基于 Rust 和 GTK 4 的 GUI 开发

use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};
const APP_ID: &str = "org.gtk_rs.HelloWorld3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button with label and margins
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(|button| {
        // Set the label to "Hello World!" after the button has been clicked on
        button.set_label("Hello World!");
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

如果您仔细查看这段代码，您会注意到它的右上角有一个小眼睛符号。按下它后，您可以看到完整代码。我们将在整本书中使用它来隐藏那些对传达信息并不重要的细节。如果您想按照本书一步步编写程序，请注意这一点。在这里，我们隐藏了我们引入gtk::Button的内容。

现在有一个按钮，如果我们单击它，它的标签将变为 “Hello World！”。

创建我们的第一个 gtk-rs 应用程序不是很难，对吧？现在让我们更好地了解我们到底在这里做了什么。

控件

控件(Widget)是组成 GTK 应用程序的组件。 GTK 提供了许多控件，如果这些控件不合适，您甚至可以自定义。例如，控件包含了显示控件、按钮、容器和窗口。一种控件可能能够包含其他控件，它可能会用于展示信息，并且可能会对交互做出反应。

Widget Gallery 有助于找出适合你的需求的控件。假设我们想向应用程序添加一个按钮。我们这里有很多选择，但让我们以最简单的一个——Button。

GTK 是一个面向对象的框架，因此所有控件都是继承树的一部分，顶部是 GObject. 继承树如下所示：

GObject
╰── Widget
    ╰── Button

GTK 文档还告诉我们，Button实现了 GtkAccessible, GtkActionable, GtkBuildable, GtkConstraintTarget 接口。

现在让我们将其与 gtk-rs 中的 Button 结构进行比较。 gtk-rs 文档告诉我们它实现了哪些 trait。我们发现这些 trait 在 GTK 文档中要么有相应的基类，要么有接口。在 “Hello World” 程序中，我们希望对按钮单击做出反应。这种行为是按钮特有的，因此我们希望在 ButtonExt trait 中找到合适的方法。而事实上，ButtonExt 包含了 connect_clicked 方法。

use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};
const APP_ID: &str = "org.gtk_rs.HelloWorld3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button with label and margins
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(|button| {
        // Set the label to "Hello World!" after the button has been clicked on
        button.set_label("Hello World!");
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

GObject 相关概念

GTK 是一个面向对象的框架。它是用 C 语言编写的，而C 语言不支持开箱即用的面向对象。这就是为什么 GTK 依赖 GObject 库来提供对象系统的原因。

我们已经了解了 gtk-rs 会将 GObject 概念（如继承和接口）映射到 Rust 的 trait 上。在本章中，我们将学习：

如何管理 GObject 的内存
如何通过子类化创建我们自己的 GObject
如何处理泛型值
如何使用属性
如何发送和接收信号

内存管理

在编写 gtk-rs 程序时，内存管理可能有点棘手。让我们来看看为什么会出现这种情况以及如何处理。

在第一个示例中，我们的窗口只有一个按钮。每点击一次按钮，一个整数变量 number 就会自增一次。

use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement0";

// DOES NOT COMPILE!
fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(application: &Application) {
    // Create two buttons
    let button_increase = Button::builder()
        .label("Increase")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // A mutable integer
    let mut number = 0;

    // Connect callbacks
    // When a button is clicked, `number` should be changed
    button_increase.connect_clicked(|_| number += 1);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(application)
        .title("My GTK App")
        .child(&button_increase)
        .build();

    // Present the window
    window.present();
}

Rust 编译器拒绝编译这个程序，同时还吐出了多条错误信息。让我们逐一查看。


error[E0373]: closure may outlive the current function, but it borrows `number`, which is owned by the current function
   |
32 |     button_increase.connect_clicked(|_| number += 1);
   |                                     ^^^ ------ `number` is borrowed here
   |                                     |
   |                                     may outlive borrowed value `number`
   |
note: function requires argument type to outlive `'static`
   |
32 |     button_increase.connect_clicked(|_| number += 1);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: to force the closure to take ownership of `number` (and any other referenced variables), use the `move` keyword
   |
32 |     button_increase.connect_clicked(move |_| number += 1);
   |

我们的闭包只借用了 number. GTK 中的信号处理器要求其引用具有静态( `static)生命周期，因此我们不能借用一个只在 build_ui 函数作用域中存在的变量。编译器也给出了解决方法。在闭包前面添加 move 关键字，number 就会被移入闭包。

use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement0";

fn main() -> glib::ExitCode {
   // Create a new application
   let app = Application::builder().application_id(APP_ID).build();

   // Connect to "activate" signal of `app`
   app.connect_activate(build_ui);

   // Run the application
   app.run()
}

fn build_ui(application: &Application) {
   // Create two buttons
   let button_increase = Button::builder()
       .label("Increase")
       .margin_top(12)
       .margin_bottom(12)
       .margin_start(12)
       .margin_end(12)
       .build();

    // DOES NOT COMPILE!
    // A mutable integer
    let mut number = 0;

    // Connect callbacks
    // When a button is clicked, `number` should be changed
    button_increase.connect_clicked(move |_| number += 1);

   // Create a window
   let window = ApplicationWindow::builder()
       .application(application)
       .title("My GTK App")
       .child(&button_increase)
       .build();

   // Present the window
   window.present();
}

但这样仍然会出现以下错误信息：


error[E0594]: cannot assign to `number`, as it is a captured variable in a `Fn` closure
   |
32 |     button_increase.connect_clicked(move |_| number += 1);
   |                                              ^^^^^^^^^^^ cannot assign

为了理解该错误信息，我们必须了解 FnOnce、FnMut 和 Fn 这三种闭包(closure) trait 之间的区别。使用实现 FnOnce 特性的闭包的 API 给 API 消费者提供了最大的自由度。闭包只被调用一次，因此它甚至可以使用自己的状态。信号处理器可以被多次调用，所以它们不能接受 FnOnce。

限制性更强的 FnMut trait 不允许闭包消耗其状态，但它们仍可以对其进行修改。信号处理器也不允许这样做，因为它们可以从自身内部调用。这将导致多个可变引用，而借用检查器根本不喜欢这种情况。

这样就只剩下 Fn. 状态可以不可变地借用，但我们如何修改 number 呢？我们需要一种具有内部可变性的数据类型，比如 std::cell::Cell.

Cell 只适用于实现了 Copy trait 的对象。对于其他对象，则应使用RefCell. 有关内部可变性的更多信息，请参见《Rust Atomics and Locks》一书中的这一部分。

文件名：listings/g_object_memory_management/1/main.rs

use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};
use std::cell::Cell;

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(application: &Application) {
    // Create two buttons
    let button_increase = Button::builder()
        .label("Increase")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // A mutable integer
    let number = Cell::new(0);

    // Connect callbacks
    // When a button is clicked, `number` should be changed
    button_increase.connect_clicked(move |_| number.set(number.get() + 1));

    // Create a window
    let window = ApplicationWindow::builder()
        .application(application)
        .title("My GTK App")
        .child(&button_increase)
        .build();

    // Present the window
    window.present();
}

现在编译结果符合预期。

让我们举一个稍微复杂一点的例子：两个按钮都修改了同一个数字number。为此，我们需要一种方法，让两个闭包都拥有同一个值的所有权？

这正是 std::rc::Rc 类型的作用。

Rc 会计算通过 Clone::clone 创建和通过 Drop::drop 释放的强引用的数量，只有当这个数量降为零时，才会释放这个值。

如果我们想修改 Rc的内容，可以再次使用 Cell 类型。

文件名：listings/g_object_memory_management/2/main.rs

use std::cell::Cell;
use std::rc::Rc;

use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}
fn build_ui(app: &Application) {
    // Create two buttons
    let button_increase = Button::builder()
        .label("Increase")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();
    let button_decrease = Button::builder()
        .label("Decrease")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Reference-counted object with inner-mutability
    let number = Rc::new(Cell::new(0));

    // Connect callbacks, when a button is clicked `number` will be changed
    let number_copy = number.clone();
    button_increase.connect_clicked(move |_| number_copy.set(number_copy.get() + 1));
    button_decrease.connect_clicked(move |_| number.set(number.get() - 1));

    // Add buttons to `gtk_box`
    let gtk_box = gtk::Box::builder()
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_increase);
    gtk_box.append(&button_decrease);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

不过，用临时变量（如 number_copy）来填充作用域并不是一件好事。

我们可以使用 glib::clone! 宏来改善这种情况。

文件名：listings/g_object_memory_management/3/main.rs

use std::cell::Cell;
use std::rc::Rc;

use glib::clone;
use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}
fn build_ui(app: &Application) {
    // Create two buttons
    let button_increase = Button::builder()
        .label("Increase")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();
    let button_decrease = Button::builder()
        .label("Decrease")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Reference-counted object with inner mutability
    let number = Rc::new(Cell::new(0));
    // Connect callbacks
    // When a button is clicked, `number` will be changed
    button_increase.connect_clicked(clone!(
        #[strong]
        number,
        move |_| {
            number.set(number.get() + 1);
        }
    ));
    button_decrease.connect_clicked(move |_| {
        number.set(number.get() - 1);
    });

    // Add buttons to `gtk_box`
    let gtk_box = gtk::Box::builder()
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_increase);
    gtk_box.append(&button_decrease);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

就像 Rc<Cell<T>>一样，GObject 也是引用计数和可变的。因此，我们可以像传递number一样将按钮传递给闭包。

文件名：listings/g_object_memory_management/4/main.rs

use std::cell::Cell;
use std::rc::Rc;

use glib::clone;
use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement4";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create two buttons
    let button_increase = Button::builder()
        .label("Increase")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();
    let button_decrease = Button::builder()
        .label("Decrease")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    let number = Rc::new(Cell::new(0));

    // Connect callbacks
    // When a button is clicked, `number` and label of the other button will be changed
    button_increase.connect_clicked(clone!(
        #[weak]
        number,
        #[strong]
        button_decrease,
        move |_| {
            number.set(number.get() + 1);
            button_decrease.set_label(&number.get().to_string());
        }
    ));
    button_decrease.connect_clicked(clone!(
        #[strong]
        button_increase,
        move |_| {
            number.set(number.get() - 1);
            button_increase.set_label(&number.get().to_string());
        }
    ));

    // Add buttons to `gtk_box`
    let gtk_box = gtk::Box::builder()
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_increase);
    gtk_box.append(&button_decrease);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

如果我们现在点击其中一个按钮，另一个按钮的标签就会改变。

但是，哎呀！我们是不是忘了引用计数系统的一个恼人之处？是的：循环引用.。button_increase 持有 button_decrease 的强引用，反之亦然。强引用可以防止引用的值被释放。如果这个链条导致一个循环，那么这个循环中的所有值都不会被释放。使用弱引用可以打破这种循环，因为弱引用不会使其值存活，而是提供了一种方法，可以在该值仍然存活时检索强引用。由于我们希望应用程序释放不需要的内存，因此我们应该在按钮上使用弱引用。

文件名：listings/g_object_memory_management/5/main.rs

use std::cell::Cell;
use std::rc::Rc;

use glib::clone;
use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement5";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create two buttons
    let button_increase = Button::builder()
        .label("Increase")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();
    let button_decrease = Button::builder()
        .label("Decrease")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Reference-counted object with inner mutability
    let number = Rc::new(Cell::new(0));

    // Connect callbacks
    // When a button is clicked, `number` and label of the other button will be changed
    button_increase.connect_clicked(clone!(
        #[weak]
        number,
        #[weak]
        button_decrease,
        move |_| {
            number.set(number.get() + 1);
            button_decrease.set_label(&number.get().to_string());
        }
    ));
    button_decrease.connect_clicked(clone!(
        #[weak]
        button_increase,
        move |_| {
            number.set(number.get() - 1);
            button_increase.set_label(&number.get().to_string());
        }
    ));

    // Add buttons to `gtk_box`
    let gtk_box = gtk::Box::builder()
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_increase);
    gtk_box.append(&button_decrease);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

现在循环引用被破坏了。

每次点击按钮时，glib::clone 都会尝试升级弱引用。例如，如果我们现在点击了一个按钮，而另一个按钮已不存在，回调将被跳过。

默认情况下，它会立即从闭包返回，返回值为 () 。如果闭包期望不同的返回值，可以指定 @default-return。

请注意，我们在第二个闭包中移动了 number。如果我们在两个闭包中都移动了弱引用，那么没有任何东西能让 number 继续存活，闭包也不会被调用。考虑到这一点，button_increase 和 button_decrease 也会在 build_ui 的作用域结束时被丢弃。那么谁来保持按钮的存活呢？

文件名：listings/g_object_memory_management/5/main.rs

use std::cell::Cell;
use std::rc::Rc;

use glib::clone;
use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement5";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create two buttons
    let button_increase = Button::builder()
        .label("Increase")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();
    let button_decrease = Button::builder()
        .label("Decrease")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Reference-counted object with inner mutability
    let number = Rc::new(Cell::new(0));

    // Connect callbacks
    // When a button is clicked, `number` and label of the other button will be changed
    button_increase.connect_clicked(clone!(
        #[weak]
        number,
        #[weak]
        button_decrease,
        move |_| {
            number.set(number.get() + 1);
            button_decrease.set_label(&number.get().to_string());
        }
    ));
    button_decrease.connect_clicked(clone!(
        #[weak]
        button_increase,
        move |_| {
            number.set(number.get() - 1);
            button_increase.set_label(&number.get().to_string());
        }
    ));

    // Add buttons to `gtk_box`
    let gtk_box = gtk::Box::builder()
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_increase);
    gtk_box.append(&button_decrease);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

当我们将按钮附加到 gtk_box 时，gtk_box 会保留对按钮的强引用。

文件名：listings/g_object_memory_management/5/main.rs

use std::cell::Cell;
use std::rc::Rc;

use glib::clone;
use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectMemoryManagement5";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create two buttons
    let button_increase = Button::builder()
        .label("Increase")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();
    let button_decrease = Button::builder()
        .label("Decrease")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Reference-counted object with inner mutability
    let number = Rc::new(Cell::new(0));

    // Connect callbacks
    // When a button is clicked, `number` and label of the other button will be changed
    button_increase.connect_clicked(clone!(
        #[weak]
        number,
        #[weak]
        button_decrease,
        move |_| {
            number.set(number.get() + 1);
            button_decrease.set_label(&number.get().to_string());
        }
    ));
    button_decrease.connect_clicked(clone!(
        #[weak]
        button_increase,
        move |_| {
            number.set(number.get() - 1);
            button_increase.set_label(&number.get().to_string());
        }
    ));

    // Add buttons to `gtk_box`
    let gtk_box = gtk::Box::builder()
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_increase);
    gtk_box.append(&button_decrease);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

当我们将 gtk_box 设置为 window 的子窗口时，window 会保持对它的强引用。

直到我们关闭窗口，它都会保持 gtk_box 以及按钮的存活。

由于我们的应用程序只有一个窗口，关闭窗口也就意味着退出应用程序。

只要尽可能使用弱引用，您就会发现完全可以避免应用程序中的循环引用。在没有循环引用的情况下，您可以依靠 GTK 来正确管理您传递给它的 GObject 的内存。

子类化

GObject 在很大程度上依赖于继承。因此，如果我们想创建一个自定义的 GObject，通过子类化来实现是很合理的。让我们用一个自定义按钮来替换 "Hello World!" 应用程序中的按钮，看看它是如何工作的。首先，我们需要创建一个实现结构体来保存状态并重写虚方法。

文件名：listings/g_object_subclassing/1/custom_button/imp.rs

use gtk::glib;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Default)]
pub struct CustomButton;

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for CustomButton {
    const NAME: &'static str = "MyGtkAppCustomButton";
    type Type = super::CustomButton;
    type ParentType = gtk::Button;
}

// Trait shared by all GObjects
impl ObjectImpl for CustomButton {}

// Trait shared by all widgets
impl WidgetImpl for CustomButton {}

// Trait shared by all buttons
impl ButtonImpl for CustomButton {}

有关子类化的说明请参见 ObjectSubclass.

NAME 应由 crate-name 和 object-name 组成，以避免名称冲突。这里应使用大驼峰命名法。
Type 指的是之后将创建的实际 GObject。
ParentType 是我们继承的 GObject。

之后，我们就可以选择重写我们祖先的虚方法。由于我们现在只想拥有一个普通按钮，所以我们什么也不重写。不过，我们仍然需要添加空的 impl。接下来，我们将描述我们自定义的 GObject 的公共接口。

文件名：listings/g_object_subclassing/1/custom_button/mod.rs

mod imp;

use glib::Object;
use gtk::glib;

glib::wrapper! {
    pub struct CustomButton(ObjectSubclass<imp::CustomButton>)
        @extends gtk::Button, gtk::Widget,
        @implements gtk::Accessible, gtk::Actionable, gtk::Buildable, gtk::ConstraintTarget;
}

impl CustomButton {
    pub fn new() -> Self {
        Object::builder().build()
    }

    pub fn with_label(label: &str) -> Self {
        Object::builder().property("label", label).build()
    }
}

impl Default for CustomButton {
    fn default() -> Self {
        Self::new()
    }
}

glib::wrapper!实现了与 ParentType 相同的 trait。理论上，这意味着 ParentType 也是我们唯一需要指定的。不幸的是，还没有人找到好的方法来做到这一点。这就是为什么到目前为止，在 Rust 中对 GObjects 进行子类化需要提及 GObject 和 GInitiallyUnowned 以外的所有祖先和接口。对于 gtk::Button，我们可以在 GTK4 的相应文档页中查找其祖先和接口。

完成这些步骤后，我们就可以用自定义按钮( CustomButton)替换 gtk::Button 了。

文件名：listings/g_object_subclassing/1/main.rs

mod custom_button;

use custom_button::CustomButton;
use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow};

const APP_ID: &str = "org.gtk_rs.GObjectSubclassing1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = CustomButton::with_label("Press me!");
    button.set_margin_top(12);
    button.set_margin_bottom(12);
    button.set_margin_start(12);
    button.set_margin_end(12);

    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |button| {
        // Set the label to "Hello World!" after the button has been clicked on
        button.set_label("Hello World!");
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

用两个结构体来描述对象是 C 语言中定义 GObject 的一种特殊方式。imp::CustomButton 处理 GObject 的状态和重写的虚方法。 CustomButton 从已实现的 trait 和添加的方法中确定要暴露的方法。

添加功能

我们可以用 CustomButton 代替 gtk::Button。这很酷，但在实际应用中不太有吸引力。尽管收益为零，但毕竟提供了不少代码模板。

所以，让我们把它变得更有趣一些吧！gtk::Button 并不会保存太多状态，但我们可以让 CustomButton 保存一个数字。

文件名：listings/g_object_subclassing/2/custom_button/imp.rs

use std::cell::Cell;

use gtk::glib;
use gtk::prelude::*;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Default)]
pub struct CustomButton {
    number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for CustomButton {
    const NAME: &'static str = "MyGtkAppCustomButton";
    type Type = super::CustomButton;
    type ParentType = gtk::Button;
}

// Trait shared by all GObjects
impl ObjectImpl for CustomButton {
    fn constructed(&self) {
        self.parent_constructed();
        self.obj().set_label(&self.number.get().to_string());
    }
}

// Trait shared by all widgets
impl WidgetImpl for CustomButton {}

// Trait shared by all buttons
impl ButtonImpl for CustomButton {
    fn clicked(&self) {
        self.number.set(self.number.get() + 1);
        self.obj().set_label(&self.number.get().to_string())
    }
}

我们在 ObjectImpl 中重写了 constructed，这样按钮的标签就会初始化为number. 我们还重写了 ButtonImpl 中的 clicked，这样每次点击都会使number自增并更新标签。

文件名：listings/g_object_subclassing/2/main.rs

mod custom_button;

use custom_button::CustomButton;
use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow};

const APP_ID: &str = "org.gtk_rs.GObjectSubclassing2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = CustomButton::new();
    button.set_margin_top(12);
    button.set_margin_bottom(12);
    button.set_margin_start(12);
    button.set_margin_end(12);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

在 build_ui 中，我们不再调用 connect_clicked，仅此而已。重新构建后，应用程序出现了标签为 "0" 的自定义按钮。每次点击按钮，标签显示的数字都会增加 1。

那么，我们什么时候需要从 GObject 继承呢？

我们想使用某个控件，但要添加状态和重写虚函数。
我们想将 Rust 对象传递给函数，但该函数需要一个 GObject。
我们想向对象添加属性或信号。

泛型值

一些与 GObject 相关的函数依赖于其参数或返回参数的泛型。由于 GObject 的内省（introspection）是通过 C 语言接口工作的，因此这些函数不能依赖于任何强大的 Rust 概念。在这种情况下，需要使用glib::Value 或 glib::Variant.

Value

我们先从 Value 开始。从概念上讲，Value 类似 Rust 的 enum ，定义如下：

enum Value <T> {
    bool(bool),
    i8(i8),
    i32(i32),
    u32(u32),
    i64(i64),
    u64(u64),
    f32(f32),
    f64(f64),
    // boxed types
    String(Option<String>),
    Object(Option<dyn IsA<glib::Object>>),
}

例如，您可以这样使用 Value 代表 i32 的值。

文件名：listings/g_object_values/1/main.rs

use gtk::prelude::*;

fn main() {
    // Store `i32` as `Value`
    let integer_value = 10.to_value();

    // Retrieve `i32` from `Value`
    let integer = integer_value
        .get::<i32>()
        .expect("The value needs to be of type `i32`.");

    // Check if the retrieved value is correct
    assert_eq!(integer, 10);

    // Store string as `Value`
    let string_value = "Hello!".to_value();

    // Retrieve `String` from `Value`
    let string = string_value
        .get::<String>()
        .expect("The value needs to be of type `String`.");

    // Check if the retrieved value is correct
    assert_eq!(string, "Hello!".to_string());

    // Store `Option<String>` as `Value`
    let string_some_value = "Hello!".to_value();
    let string_none_value = None::<String>.to_value();

    // Retrieve `String` from `Value`
    let string_some = string_some_value
        .get::<Option<String>>()
        .expect("The value needs to be of type `Option<String>`.");
    let string_none = string_none_value
        .get::<Option<String>>()
        .expect("The value needs to be of type `Option<String>`.");

    // Check if the retrieved value is correct
    assert_eq!(string_some, Some("Hello!".to_string()));
    assert_eq!(string_none, None);
}

还要注意的是，在上述枚举中，String 或 glib::Object 等 boxed 类型被封装在一个 Option 中。这源于 C 语言，在 C 语言中，每个 boxed 类型都有可能是 None（或 NULL）。您仍然可以按照与上述 i32 相同的方式访问它。如果指定了错误的类型，get 会返回 Err，而且如果 Value 代表 None，也会返回 Err。

文件名：listings/g_object_values/1/main.rs

use gtk::prelude::*;

fn main() {
    // Store `i32` as `Value`
    let integer_value = 10.to_value();

    // Retrieve `i32` from `Value`
    let integer = integer_value
        .get::<i32>()
        .expect("The value needs to be of type `i32`.");

    // Check if the retrieved value is correct
    assert_eq!(integer, 10);

    // Store string as `Value`
    let string_value = "Hello!".to_value();

    // Retrieve `String` from `Value`
    let string = string_value
        .get::<String>()
        .expect("The value needs to be of type `String`.");

    // Check if the retrieved value is correct
    assert_eq!(string, "Hello!".to_string());

    // Store `Option<String>` as `Value`
    let string_some_value = "Hello!".to_value();
    let string_none_value = None::<String>.to_value();

    // Retrieve `String` from `Value`
    let string_some = string_some_value
        .get::<Option<String>>()
        .expect("The value needs to be of type `Option<String>`.");
    let string_none = string_none_value
        .get::<Option<String>>()
        .expect("The value needs to be of type `Option<String>`.");

    // Check if the retrieved value is correct
    assert_eq!(string_some, Some("Hello!".to_string()));
    assert_eq!(string_none, None);
}

如果要区分是指定了错误的类型还是 Value 值为 None ，只需调用 get::<Option<T>> 即可。

文件名：listings/g_object_values/1/main.rs

use gtk::prelude::*;

fn main() {
    // Store `i32` as `Value`
    let integer_value = 10.to_value();

    // Retrieve `i32` from `Value`
    let integer = integer_value
        .get::<i32>()
        .expect("The value needs to be of type `i32`.");

    // Check if the retrieved value is correct
    assert_eq!(integer, 10);

    // Store string as `Value`
    let string_value = "Hello!".to_value();

    // Retrieve `String` from `Value`
    let string = string_value
        .get::<String>()
        .expect("The value needs to be of type `String`.");

    // Check if the retrieved value is correct
    assert_eq!(string, "Hello!".to_string());

    // Store `Option<String>` as `Value`
    let string_some_value = "Hello!".to_value();
    let string_none_value = None::<String>.to_value();

    // Retrieve `String` from `Value`
    let string_some = string_some_value
        .get::<Option<String>>()
        .expect("The value needs to be of type `Option<String>`.");
    let string_none = string_none_value
        .get::<Option<String>>()
        .expect("The value needs to be of type `Option<String>`.");

    // Check if the retrieved value is correct
    assert_eq!(string_some, Some("Hello!".to_string()));
    assert_eq!(string_none, None);
}

我们将在后面处理属性和信号时使用 Value。

Variant

当数据需要序列化时，例如将数据发送到另一个进程、发送到网络上，或将数据存储到磁盘时，就会用到Variant. 虽然 GVariant 支持任意复杂的类型，但 Rust 绑定目前仅限于bool, u8, i16, u16, i32, u32, i64, u64, f64, &str/String 和 VariantDict. 上述类型的容器也可以使用，如 HashMap、Vec、Option、最多 16 个元素的元组(tuple)和 Variant。只要 Rust 结构体的成员可以用Variant表示，Variant甚至可以从 Rust 结构体派生。

在最简单的情况下，将 Rust 类型转换为 Variant 或反向转换，与处理 Value 的方式非常相似。

文件名：listings/g_object_values/2/main.rs

use gtk::prelude::*;

fn main() {
    // Store `i32` as `Variant`
    let integer_variant = 10.to_variant();

    // Retrieve `i32` from `Variant`
    let integer = integer_variant
        .get::<i32>()
        .expect("The variant needs to be of type `i32`.");

    // Check if the retrieved value is correct
    assert_eq!(integer, 10);

    let variant = vec!["Hello", "there!"].to_variant();
    assert_eq!(variant.n_children(), 2);
    let vec = &variant
        .get::<Vec<String>>()
        .expect("The variant needs to be of type `String`.");
    assert_eq!(vec[0], "Hello");
}

不过，Variant 也可以表示 HashMap 或 Vec 等容器。下面的代码段展示了如何在 Vec 和 Variant 之间进行转换。更多示例请参见文档。

文件名：listings/g_object_values/2/main.rs

use gtk::prelude::*;

fn main() {
    // Store `i32` as `Variant`
    let integer_variant = 10.to_variant();

    // Retrieve `i32` from `Variant`
    let integer = integer_variant
        .get::<i32>()
        .expect("The variant needs to be of type `i32`.");

    // Check if the retrieved value is correct
    assert_eq!(integer, 10);

    let variant = vec!["Hello", "there!"].to_variant();
    assert_eq!(variant.n_children(), 2);
    let vec = &variant
        .get::<Vec<String>>()
        .expect("The variant needs to be of type `String`.");
    assert_eq!(vec[0], "Hello");
}

我们将在使用 gio::Settings 保存设置或通过 gio::Action 激活操作时使用 Variant.

属性

属性(Properties)为访问 GObject 的状态提供了一个公共 API.

让我们通过 Switch 控件来看看如何实现这一点。它的一个属性叫做 active. 根据 GTK 文档，它可以被读取和写入。因此，gtk-rs 提供了相应的 is_active 和 set_active 方法。

文件名：listings/g_object_properties/1/main.rs

use gtk::prelude::*;
use gtk::{glib, Align, Application, ApplicationWindow, Box, Orientation, Switch};

const APP_ID: &str = "org.gtk_rs.GObjectProperties1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create the switch
    let switch = Switch::new();

    // Set and then immediately obtain active property
    switch.set_active(true);
    let switch_active = switch.is_active();

    // This prints: "The active property of switch is true"
    println!("The active property of switch is {}", switch_active);

    // Set up box
    let gtk_box = Box::builder()
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .valign(Align::Center)
        .halign(Align::Center)
        .spacing(12)
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&switch);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

属性不仅可以通过 getter 和 setter 访问，还可以相互绑定。让我们看看两个 Switch 实例是如何绑定的。

文件名：listings/g_object_properties/2/main.rs

use gtk::prelude::*;
use gtk::{glib, Align, Application, ApplicationWindow, Box, Orientation, Switch};

const APP_ID: &str = "org.gtk_rs.GObjectProperties3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create the switches
    let switch_1 = Switch::new();
    let switch_2 = Switch::new();

    switch_1
        .bind_property("active", &switch_2, "active")
        .bidirectional()
        .build();

    // Set up box
    let gtk_box = Box::builder()
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .valign(Align::Center)
        .halign(Align::Center)
        .spacing(12)
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&switch_1);
    gtk_box.append(&switch_2);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

在本例中，我们希望将 switch_1 的 "active" 属性与 switch_2 的 "active" 属性绑定。我们还希望绑定是双向的，因此通过调用 bidirectional 方法来指定。

文件名：listings/g_object_properties/2/main.rs

use gtk::prelude::*;
use gtk::{glib, Align, Application, ApplicationWindow, Box, Orientation, Switch};

const APP_ID: &str = "org.gtk_rs.GObjectProperties3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create the switches
    let switch_1 = Switch::new();
    let switch_2 = Switch::new();

    switch_1
        .bind_property("active", &switch_2, "active")
        .bidirectional()
        .build();

    // Set up box
    let gtk_box = Box::builder()
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .valign(Align::Center)
        .halign(Align::Center)
        .spacing(12)
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&switch_1);
    gtk_box.append(&switch_2);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

现在，当我们点击两个开关中的一个时，另一个也会被切换。

给自定义 GObject 添加属性

我们还可以为自定义 GObject 添加属性。我们可以通过将 CustomButton 的 number 绑定到一个属性来演示这一点。大部分工作由 glib::Properties 派生宏(derive macro)完成。我们告诉它封装类型是 super::CustomButton。我们还给 number 添加了注释，这样宏就知道它应该创建一个可读可写的属性 "number"。宏还会生成本章稍后将使用的封装方法。

文件名：listings/g_object_properties/3/custom_button/imp.rs

use std::cell::Cell;

use glib::Properties;
use gtk::glib;
use gtk::prelude::*;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Properties, Default)]
#[properties(wrapper_type = super::CustomButton)]
pub struct CustomButton {
    #[property(get, set)]
    number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for CustomButton {
    const NAME: &'static str = "MyGtkAppCustomButton";
    type Type = super::CustomButton;
    type ParentType = gtk::Button;
}

// Trait shared by all GObjects
#[glib::derived_properties]
impl ObjectImpl for CustomButton {
    fn constructed(&self) {
        self.parent_constructed();

        // Bind label to number
        // `SYNC_CREATE` ensures that the label will be immediately set
        let obj = self.obj();
        obj.bind_property("number", obj.as_ref(), "label")
            .sync_create()
            .build();
    }
}

// Trait shared by all widgets
impl WidgetImpl for CustomButton {}

// Trait shared by all buttons
impl ButtonImpl for CustomButton {
    fn clicked(&self) {
        let incremented_number = self.obj().number() + 1;
        self.obj().set_number(incremented_number);
    }
}

glib::derived_properties 宏为每个使用 Property 宏生成属性的 GObject 生成了模板。在 constructed 中，我们通过绑定 "label "属性来使用新属性 "number"。bind_property 会自行将 "number "的整数值转换为 "label "的字符串。现在，我们不必再在 "clicked" 回调函数中调整标签了。

文件名：listings/g_object_properties/3/custom_button/imp.rs

use std::cell::Cell;

use glib::Properties;
use gtk::glib;
use gtk::prelude::*;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Properties, Default)]
#[properties(wrapper_type = super::CustomButton)]
pub struct CustomButton {
    #[property(get, set)]
    number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for CustomButton {
    const NAME: &'static str = "MyGtkAppCustomButton";
    type Type = super::CustomButton;
    type ParentType = gtk::Button;
}

// Trait shared by all GObjects
#[glib::derived_properties]
impl ObjectImpl for CustomButton {
    fn constructed(&self) {
        self.parent_constructed();

        // Bind label to number
        // `SYNC_CREATE` ensures that the label will be immediately set
        let obj = self.obj();
        obj.bind_property("number", obj.as_ref(), "label")
            .sync_create()
            .build();
    }
}

// Trait shared by all widgets
impl WidgetImpl for CustomButton {}

// Trait shared by all buttons
impl ButtonImpl for CustomButton {
    fn clicked(&self) {
        let incremented_number = self.obj().number() + 1;
        self.obj().set_number(incremented_number);
    }
}

我们还必须调整 clicked 方法。以前我们直接修改 number，现在我们可以使用生成的封装方法 number 和 set_number。这样就会发出 "notify "信号，这对于绑定正常工作是必要的。

use std::cell::Cell;

use glib::Properties;
use gtk::glib;
use gtk::prelude::*;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Properties, Default)]
#[properties(wrapper_type = super::CustomButton)]
pub struct CustomButton {
    #[property(get, set)]
    number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for CustomButton {
    const NAME: &'static str = "MyGtkAppCustomButton";
    type Type = super::CustomButton;
    type ParentType = gtk::Button;
}

// Trait shared by all GObjects
#[glib::derived_properties]
impl ObjectImpl for CustomButton {
    fn constructed(&self) {
        self.parent_constructed();

        // Bind label to number
        // `SYNC_CREATE` ensures that the label will be immediately set
        let obj = self.obj();
        obj.bind_property("number", obj.as_ref(), "label")
            .sync_create()
            .build();
    }
}

// Trait shared by all widgets
impl WidgetImpl for CustomButton {}

// Trait shared by all buttons
impl ButtonImpl for CustomButton {
    fn clicked(&self) {
        let incremented_number = self.obj().number() + 1;
        self.obj().set_number(incremented_number);
    }
}

让我们通过创建两个自定义按钮来看看能做些什么。

文件名：listings/g_object_properties/3/main.rs

mod custom_button;

use custom_button::CustomButton;
use gtk::prelude::*;
use gtk::{glib, Align, Application, ApplicationWindow, Box, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectProperties4";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create the buttons
    let button_1 = CustomButton::new();
    let button_2 = CustomButton::new();

    // Assure that "number" of `button_2` is always 1 higher than "number" of `button_1`
    button_1
        .bind_property("number", &button_2, "number")
        // How to transform "number" from `button_1` to "number" of `button_2`
        .transform_to(|_, number: i32| {
            let incremented_number = number + 1;
            Some(incremented_number.to_value())
        })
        // How to transform "number" from `button_2` to "number" of `button_1`
        .transform_from(|_, number: i32| {
            let decremented_number = number - 1;
            Some(decremented_number.to_value())
        })
        .bidirectional()
        .sync_create()
        .build();

    // The closure will be called
    // whenever the property "number" of `button_1` gets changed
    button_1.connect_number_notify(|button| {
        println!("The current number of `button_1` is {}.", button.number());
    });

    // Set up box
    let gtk_box = Box::builder()
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .valign(Align::Center)
        .halign(Align::Center)
        .spacing(12)
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_1);
    gtk_box.append(&button_2);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

我们已经看到，绑定的属性不一定必须是同一类型。利用 transform_to 和 transform_from, 我们可以确保 button_2 显示的数字总是比 button_1 显示的数字大 1.

文件名：listings/g_object_properties/3/main.rs

mod custom_button;

use custom_button::CustomButton;
use gtk::prelude::*;
use gtk::{glib, Align, Application, ApplicationWindow, Box, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectProperties4";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create the buttons
    let button_1 = CustomButton::new();
    let button_2 = CustomButton::new();

    // Assure that "number" of `button_2` is always 1 higher than "number" of `button_1`
    button_1
        .bind_property("number", &button_2, "number")
        // How to transform "number" from `button_1` to "number" of `button_2`
        .transform_to(|_, number: i32| {
            let incremented_number = number + 1;
            Some(incremented_number.to_value())
        })
        // How to transform "number" from `button_2` to "number" of `button_1`
        .transform_from(|_, number: i32| {
            let decremented_number = number - 1;
            Some(decremented_number.to_value())
        })
        .bidirectional()
        .sync_create()
        .build();

    // The closure will be called
    // whenever the property "number" of `button_1` gets changed
    button_1.connect_number_notify(|button| {
        println!("The current number of `button_1` is {}.", button.number());
    });

    // Set up box
    let gtk_box = Box::builder()
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .valign(Align::Center)
        .halign(Align::Center)
        .spacing(12)
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_1);
    gtk_box.append(&button_2);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

现在，如果我们点击其中一个按钮，另一个按钮的 "number" 和 "label" 属性也会随之改变。

属性的另一个优点是，当属性发生变化时，可以将回调连接到事件。例如：

文件名：listings/g_object_properties/3/main.rs

mod custom_button;

use custom_button::CustomButton;
use gtk::prelude::*;
use gtk::{glib, Align, Application, ApplicationWindow, Box, Orientation};

const APP_ID: &str = "org.gtk_rs.GObjectProperties4";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create the buttons
    let button_1 = CustomButton::new();
    let button_2 = CustomButton::new();

    // Assure that "number" of `button_2` is always 1 higher than "number" of `button_1`
    button_1
        .bind_property("number", &button_2, "number")
        // How to transform "number" from `button_1` to "number" of `button_2`
        .transform_to(|_, number: i32| {
            let incremented_number = number + 1;
            Some(incremented_number.to_value())
        })
        // How to transform "number" from `button_2` to "number" of `button_1`
        .transform_from(|_, number: i32| {
            let decremented_number = number - 1;
            Some(decremented_number.to_value())
        })
        .bidirectional()
        .sync_create()
        .build();

    // The closure will be called
    // whenever the property "number" of `button_1` gets changed
    button_1.connect_number_notify(|button| {
        println!("The current number of `button_1` is {}.", button.number());
    });

    // Set up box
    let gtk_box = Box::builder()
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .valign(Align::Center)
        .halign(Align::Center)
        .spacing(12)
        .orientation(Orientation::Vertical)
        .build();
    gtk_box.append(&button_1);
    gtk_box.append(&button_2);

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&gtk_box)
        .build();

    // Present the window
    window.present();
}

现在，每当 "number" 属性发生变化时，闭包就会被执行，并将 "number" 的当前值打印到标准输出中。

将属性引入您的自定义 GObject 将会非常有用，如果您想：

绑定（不同）GObject 的状态
在属性值发生变化时通知消费者

请注意，每次值发生变化时发送信号都会产生（计算）代价。如果您只想暴露内部状态，添加 getter 和 setter 方法是更好的选择。

信号

GObject 信号是一个为特定事件注册回调的系统。例如，如果我们按下一个按钮，"clicked（点击）"信号就会发出。然后，该信号将负责执行所有已注册的回调函数。

gtk-rs 提供了注册回调的便捷方法。在我们的 "Hello World" 示例中，我们将 "clicked" 信号连接到一个闭包，一旦它被调用，就会将按钮的标签设置为 "Hello World"。

use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};
const APP_ID: &str = "org.gtk_rs.HelloWorld3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button with label and margins
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(|button| {
        // Set the label to "Hello World!" after the button has been clicked on
        button.set_label("Hello World!");
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

如果我们愿意，可以使用通用的 connect_closure 方法和 glib::closure_local! 宏来连接它。

文件名：listings/g_object_signals/1/main.rs

use glib::closure_local;
use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.GObjectSignals1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_closure(
        "clicked",
        false,
        closure_local!(move |button: Button| {
            // Set the label to "Hello World!" after the button has been clicked on
            button.set_label("Hello World!");
        }),
    );


    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

connect_closure 的优势在于它还能与自定义信号一起使用。

如果您需要在闭包中克隆引用计数对象，则不必将其封装在另一个clone! 宏中。 closure_local! 接受与创建强/弱引用相同的语法，并具有监视功能，一旦监视对象被删除，闭包就会自动断开连接。

向自定义 GObject 添加信号

让我们看看如何创建自己的信号。现在，让我们可以来扩展 CustomButton。首先，我们覆盖 ObjectImpl 中的 signals 方法。 std::sync::OnceLock 可以确保 SIGNALS 只被初始化一次。

文件名：listings/g_object_signals/2/custom_button/imp.rs

use std::cell::Cell;
use std::sync::OnceLock;

use glib::subclass::Signal;
use glib::Properties;
use gtk::glib;
use gtk::prelude::*;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Properties, Default)]
#[properties(wrapper_type = super::CustomButton)]
pub struct CustomButton {
    #[property(get, set)]
    number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for CustomButton {
    const NAME: &'static str = "MyGtkAppCustomButton";
    type Type = super::CustomButton;
    type ParentType = gtk::Button;
}

// Trait shared by all GObjects
#[glib::derived_properties]
impl ObjectImpl for CustomButton {
    fn signals() -> &'static [Signal] {
        static SIGNALS: OnceLock<Vec<Signal>> = OnceLock::new();
        SIGNALS.get_or_init(|| {
            vec![Signal::builder("max-number-reached")
                .param_types([i32::static_type()])
                .build()]
        })
    }

    fn constructed(&self) {
        self.parent_constructed();

        // Bind label to number
        // `SYNC_CREATE` ensures that the label will be immediately set
        let obj = self.obj();
        obj.bind_property("number", obj.as_ref(), "label")
            .sync_create()
            .build();
    }
}

// Trait shared by all widgets
impl WidgetImpl for CustomButton {}

static MAX_NUMBER: i32 = 8;

// Trait shared by all buttons
impl ButtonImpl for CustomButton {
    fn clicked(&self) {
        let incremented_number = self.obj().number() + 1;
        let obj = self.obj();
        // If `number` reached `MAX_NUMBER`,
        // emit "max-number-reached" signal and set `number` back to 0
        if incremented_number == MAX_NUMBER {
            obj.emit_by_name::<()>("max-number-reached", &[&incremented_number]);
            obj.set_number(0);
        } else {
            obj.set_number(incremented_number);
        }
    }
}

signals 方法负责定义一组信号。在本例中，我们只创建了一个名为 "max-number-reached" 的信号。在命名信号时，我们确保使用短横线命名法(kebab-case)进行命名。当信号发出时，它会发送一个 i32 值。

我们希望在number 达到 MAX_NUMBER 时发出信号。在发送信号的同时，我们还将发送 number 当前的值。之后，我们将number 重置为 0.

文件名：listings/g_object_signals/2/custom_button/imp.rs

use std::cell::Cell;
use std::sync::OnceLock;

use glib::subclass::Signal;
use glib::Properties;
use gtk::glib;
use gtk::prelude::*;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Properties, Default)]
#[properties(wrapper_type = super::CustomButton)]
pub struct CustomButton {
    #[property(get, set)]
    number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for CustomButton {
    const NAME: &'static str = "MyGtkAppCustomButton";
    type Type = super::CustomButton;
    type ParentType = gtk::Button;
}

// Trait shared by all GObjects
#[glib::derived_properties]
impl ObjectImpl for CustomButton {
    fn signals() -> &'static [Signal] {
        static SIGNALS: OnceLock<Vec<Signal>> = OnceLock::new();
        SIGNALS.get_or_init(|| {
            vec![Signal::builder("max-number-reached")
                .param_types([i32::static_type()])
                .build()]
        })
    }

    fn constructed(&self) {
        self.parent_constructed();

        // Bind label to number
        // `SYNC_CREATE` ensures that the label will be immediately set
        let obj = self.obj();
        obj.bind_property("number", obj.as_ref(), "label")
            .sync_create()
            .build();
    }
}

// Trait shared by all widgets
impl WidgetImpl for CustomButton {}

static MAX_NUMBER: i32 = 8;

// Trait shared by all buttons
impl ButtonImpl for CustomButton {
    fn clicked(&self) {
        let incremented_number = self.obj().number() + 1;
        let obj = self.obj();
        // If `number` reached `MAX_NUMBER`,
        // emit "max-number-reached" signal and set `number` back to 0
        if incremented_number == MAX_NUMBER {
            obj.emit_by_name::<()>("max-number-reached", &[&incremented_number]);
            obj.set_number(0);
        } else {
            obj.set_number(incremented_number);
        }
    }
}

如果我们现在按下按钮，其标签上的数字就会增加，直到达到 MAX_NUMBER. 然后它会发出 "max-number-reached" 信号，我们可以很好地连接到该信号。现在，每当我们收到 "max-number-reached" 信号时，相应的数字就会打印到标准输出中。

Filename: listings/g_object_signals/2/main.rs

mod custom_button;

use custom_button::CustomButton;
use glib::closure_local;
use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow};

const APP_ID: &str = "org.gtk_rs.GObjectSignals2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}
fn build_ui(app: &Application) {
    // Create a button
    let button = CustomButton::new();
    button.set_margin_top(12);
    button.set_margin_bottom(12);
    button.set_margin_start(12);
    button.set_margin_end(12);

    button.connect_closure(
        "max-number-reached",
        false,
        closure_local!(move |_button: CustomButton, number: i32| {
            println!("The maximum number {} has been reached", number);
        }),
    );

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

现在，您已经知道如何连接各种信号以及如何创建自己的信号。如果您想通知 GObject 的消费者发生了某一事件，自定义信号尤其有用。

主事件循环

我们现在已经能自如地使用回调了，但它们究竟是如何工作的呢？所有这些都是异步发生的，因此必须有一个东西来管理事件和调度响应。不出所料，这就是所谓的主事件循环。

主循环管理各种事件——从鼠标点击、键盘按下到文件事件。所有这些工作都在同一线程内完成。在所有任务之间快速迭代会给人一种并行的错觉。这就是为什么你可以在进度条增长的同时移动窗口。

不过，你肯定见过图形界面无响应，至少有几秒钟是这样。当单个任务耗时过长时，就会出现这种情况。下面的示例使用 std::thread::sleep 来表示一个长时间运行的任务。

文件名：listings/main_event_loop/1/main.rs

use std::thread;
use std::time::Duration;

use gtk::prelude::*;
use gtk::{self, glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.MainEventLoop1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |_| {
        // GUI is blocked for 5 seconds after the button is pressed
        let five_seconds = Duration::from_secs(5);
        thread::sleep(five_seconds);
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

按下按钮后，界面会完全冻结五秒钟。我们甚至无法移动窗口。调用sleep是一个人为的例子，但我们经常希望一次性运行一个时间稍长的操作。

如何避免阻塞主循环

为了避免阻塞主循环，我们可以使用 gio::spawn_blocking 生成一个新任务，让操作在线程池中运行。

文件名：listings/main_event_loop/2/main.rs

use std::thread;
use std::time::Duration;

use gtk::prelude::*;
use gtk::{self, gio, glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.MainEventLoop2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |_| {
        // The long running operation runs now in a separate thread
        gio::spawn_blocking(move || {
            let five_seconds = Duration::from_secs(5);
            thread::sleep(five_seconds);
        });
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

现在，当我们按下按钮时，界面不会冻结。但是，每按一次按钮就会生成一个新任务。这不一定是我们想要的。

如果你来自 Rust 之外的其他语言，那么在考虑其他选项之前，你可能会对在独立线程中运行任务的想法感到不舒服。幸运的是，Rust 的安全保证让你不再担心并发会带来令人讨厌的错误。

通道

通常，我们希望跟踪任务中的工作。在我们的例子中，我们不希望用户在现有任务仍在运行时产生额外的任务。为了与任务交换信息，我们可以使用 async-channel 创建一个通道。让我们在终端执行以下命令来添加它：

cargo add async-channel

我们要发送一个 bool 值，以告知是否希望按钮对点击做出反应。由于我们在单独的线程中发送，因此可以使用 send_blocking. 那接收呢？每次收到消息时，我们都想根据收到的 bool 设置按钮的灵敏度。但是，我们不想在等待接收消息时阻塞主循环。毕竟这才是整个练习的重点！

我们通过在一个异步(async)代码块中等待消息来解决这个问题。这个异步代码块在 glib 主循环中使用 spawn_future_local 生成。

另请参阅 spawn_future ，从主线程外在主循环上生成异步代码块。

文件名：listings/main_event_loop/3/main.rs

use std::thread;
use std::time::Duration;

use glib::clone;
use gtk::prelude::*;
use gtk::{gio, glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.MainEventLoop3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Create channel that can hold at most 1 message at a time
    let (sender, receiver) = async_channel::bounded(1);
    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |_| {
        let sender = sender.clone();
        // The long running operation runs now in a separate thread
        gio::spawn_blocking(move || {
            // Deactivate the button until the operation is done
            sender
                .send_blocking(false)
                .expect("The channel needs to be open.");
            let five_seconds = Duration::from_secs(5);
            thread::sleep(five_seconds);
            // Activate the button again
            sender
                .send_blocking(true)
                .expect("The channel needs to be open.");
        });
    });

    // The main loop executes the asynchronous block
    glib::spawn_future_local(clone!(
        #[weak]
        button,
        async move {
            while let Ok(enable_button) = receiver.recv().await {
                button.set_sensitive(enable_button);
            }
        }
    ));

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

正如你所看到的，生成一个任务仍然不会冻结我们的用户界面。不过，现在我们无法同时启动多个任务，因为在启动第一个任务后，按钮就变得不敏感了。任务完成后，按钮又会变得敏感。

如果任务本质上是异步的怎么办？让我们尝试用 [`glib::timeout_future_seconds`](https://gtk-rs.org/gtk-rs-core/stable/latest/docs/glib/fn.timeout_future_seconds.html) 代替 `std::thread::sleep` 来表示我们的任务。它返回一个 [`std::future::Future`](https://doc.rust-lang.org/std/future/trait.Future.html)，这意味着我们可以在异步上下文中等待它。转换后的代码在外观和行为上与多线程代码非常相似。

文件名：listings/main_event_loop/4/main.rs

use glib::clone;
use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.MainEventLoop4";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Create channel that can hold at most 1 message at a time
    let (sender, receiver) = async_channel::bounded(1);
    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |_| {
        glib::spawn_future_local(clone!(
            #[strong]
            sender,
            async move {
                // Deactivate the button until the operation is done
                sender
                    .send(false)
                    .await
                    .expect("The channel needs to be open.");
                glib::timeout_future_seconds(5).await;
                // Activate the button again
                sender
                    .send(true)
                    .await
                    .expect("The channel needs to be open.");
            }
        ));
    });

    // The main loop executes the asynchronous block
    glib::spawn_future_local(clone!(
        #[weak]
        button,
        async move {
            while let Ok(enable_button) = receiver.recv().await {
                button.set_sensitive(enable_button);
            }
        }
    ));

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

由于我们又是单线程运行，我们甚至可以不需要通道并实现相同结果。

文件名：listings/main_event_loop/5/main.rs

use glib::clone;
use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.MainEventLoop5";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |button| {
        glib::spawn_future_local(clone!(
            #[weak]
            button,
            async move {
                // Deactivate the button until the operation is done
                button.set_sensitive(false);
                glib::timeout_future_seconds(5).await;
                // Activate the button again
                button.set_sensitive(true);
            }
        ));
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

但我们为什么不在多线程示例中做同样的事情呢？

use std::{thread, time::Duration};

use glib::{clone, MainContext, PRIORITY_DEFAULT};
use gtk::{glib, gio};
use gtk::prelude::*;
use gtk::{Application, ApplicationWindow, Button};

fn main() {
    // Create a new application
    let app = Application::builder()
       .application_id("org.gtk_rs.MainEventLoop6")
       .build();

    // Connect to "activate" signal
    app.connect_activate(build_ui);

    // Get command-line arguments
    let args: Vec<String> = args().collect();
    // Run the application
    app.run(&args);
}

// When the application is launched…
fn build_ui(application: &Application) {
    // Create a window
    let window = ApplicationWindow::builder()
        .application(application)
        .title("My GTK App")
        .build();

    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // DOES NOT COMPILE!
    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |button| {
        button.clone();
        // The long running operation runs now in a separate thread
        gio::spawn_blocking(move || {
            // Deactivate the button until the operation is done
            button.set_sensitive(false);
            let five_seconds = Duration::from_secs(5);
            thread::sleep(five_seconds);
            // Activate the button again
            button.set_sensitive(true);
        });
    });

    // Add button
    window.set_child(Some(&button));
    window.present();
}

原因很简单，因为我们会收到这样的错误信息：

error[E0277]: `NonNull<GObject>` cannot be shared between threads safely

help: within `gtk4::Button`, the trait `Sync` is not implemented for `NonNull<GObject>`

经过循环引用后，我们发现了 GTK GObjects 的第二个缺点：它们不是线程安全的。

在 `async` 上下文中嵌入阻塞调用

在前面的代码片段中，我们已经看到在 glib 主循环中生成一个 async 块或 async future 比在独立线程上运行任务能带来更简洁的代码。在 gtk-rs 应用中执行 async 函数时，我们还可以关注一些有趣的方面。

首先，阻塞函数可以嵌入 async 上下文中。在下面的列表中，我们要执行一个同步函数，该函数返回一个布尔值，运行时间为 10 秒。为了将其集成到 async 代码块中，我们通过 spawn_blocking 在单独的线程中运行该函数。然后，我们可以在 spawn_blocking 的返回值上调用 await 来获取函数的返回值。

文件名：listings/main_event_loop/6/main.rs

use glib::clone;
use gtk::prelude::*;
use gtk::{gio, glib};
use gtk::{Application, ApplicationWindow, Button};
use std::thread;
use std::time::Duration;

const APP_ID: &str = "org.gtk_rs.MainEventLoop6";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |button| {
        // The main loop executes the asynchronous block
        glib::spawn_future_local(clone!(
            #[weak]
            button,
            async move {
                // Deactivate the button until the operation is done
                button.set_sensitive(false);
                let enable_button = gio::spawn_blocking(move || {
                    let five_seconds = Duration::from_secs(5);
                    thread::sleep(five_seconds);
                    true
                })
                .await
                .expect("Task needs to finish successfully.");
                // Set sensitivity of button to `enable_button`
                button.set_sensitive(enable_button);
            }
        ));
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

从外部 crate 运行异步函数

glib 生态系统中的异步函数总是可以在 glib 主循环中生成。通常情况下，依赖于 async-std 或 smol 的 crate 也可以工作。以 ashpd 为例，它允许沙箱应用程序与桌面交互。默认情况下，它依赖于 async-std。我们可以通过运行以下命令将其添加到我们的依赖中。

cargo add ashpd --features gtk4

您需要使用 Linux 桌面环境才能在本地运行下面的示例。此示例使用 ashpd::desktop::account::UserInformation 访问用户信息。我们从按钮获取一个 gtk::Native 对象，创建一个 ashp::WindowIdentifier 并将其传递给用户信息请求。

我们需要通过 WindowIdentifier 使对话框成为模态对话框。这意味着对话框将位于窗口顶部，并冻结应用程序的其他部分，不让用户输入。

Filename: listings/main_event_loop/7/main.rs

use ashpd::desktop::account::UserInformation;
use ashpd::WindowIdentifier;
use glib::clone;
use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.MainEventLoop7";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |button| {
        // The main loop executes the asynchronous block
        glib::spawn_future_local(clone!(
            #[weak]
            button,
            async move {
                // Get native of button for window identifier
                let native = button.native().expect("Need to be able to get native.");
                // Get window identifier so that the dialog will be modal to the main window
                let identifier = WindowIdentifier::from_native(&native).await;
                let request = UserInformation::request()
                    .reason("App would like to access user information.")
                    .identifier(identifier)
                    .send()
                    .await;

                if let Ok(response) = request.and_then(|r| r.response()) {
                    println!("User name: {}", response.name());
                } else {
                    println!("Could not access user information.")
                }
            }
        ));
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

按下按钮后，会打开一个对话框，显示将要共享的信息。如果您决定共享，您的用户名将被打印在控制台上。

Tokio

tokio 是 Rust 最流行的异步平台。因此，许多高质量的 crate 都是其生态系统的一部分。网络客户端 reqwest 就属于这一类。让我们执行以下命令来添加它

cargo add reqwest@0.12 --features rustls-tls --no-default-features

一旦按下按钮，我们就会向 www.gtk-rs.org 发送 GET 请求。然后通过通道将响应发送到主线程。

文件名：listings/main_event_loop/8/main.rs

use glib::clone;
use gtk::glib;
use gtk::prelude::*;
use gtk::{Application, ApplicationWindow, Button};

const APP_ID: &str = "org.gtk_rs.MainEventLoop8";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    let (sender, receiver) = async_channel::bounded(1);
    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |_| {
        // The main loop executes the asynchronous block
        glib::spawn_future_local(clone!(
            #[strong]
            sender,
            async move {
                let response = reqwest::get("https://www.gtk-rs.org").await;
                sender
                    .send(response)
                    .await
                    .expect("The channel needs to be open.");
            }
        ));
    });

    // The main loop executes the asynchronous block
    glib::spawn_future_local(async move {
        while let Ok(response) = receiver.recv().await {
            if let Ok(response) = response {
                println!("Status: {}", response.status());
            } else {
                println!("Could not make a `GET` request.");
            }
        }
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

编译正常，甚至似乎可以运行。但是，当我们按下按钮时却什么也没发生。检查控制台时发现了以下错误信息：

thread 'main' panicked at
'there is no reactor running, must be called from the context of a Tokio 1.x runtime'

在撰写本文时，reqwest 没有说明这一要求。不幸的是，其他依赖 tokio 的库也是如此。让我们咬咬牙，添加 tokio：

cargo add tokio@1 --features rt-multi-thread

由于我们已经在主线程上运行了 glib 主循环，因此我们不想在主线程上运行 tokio 运行时。因此，我们要避免使用 #[tokio::main] 宏或顶级 block_on 调用。这样做会阻塞运行时的一个线程与 GLib 主循环，既浪费资源，又可能产生奇怪的 bug。

相反，我们将 tokio::runtime::Runtime 与静态变量绑定。

use std::sync::OnceLock;

use glib::clone;
use gtk::glib;
use gtk::prelude::*;
use gtk::{Application, ApplicationWindow, Button};
use tokio::runtime::Runtime;

const APP_ID: &str = "org.gtk_rs.MainEventLoop0";

// DOES NOT COMPILE!
static RUNTIME: Runtime =
    Runtime::new().expect("Setting up tokio runtime needs to succeed.");

fn main() -> glib::ExitCode {
   // Create a new application
   let app = Application::builder().application_id(APP_ID).build();

   // Connect to "activate" signal of `app`
   app.connect_activate(build_ui);

   // Run the application
   app.run()
}

fn build_ui(app: &Application) {
   // Create a button
   let button = Button::builder()
       .label("Press me!")
       .margin_top(12)
       .margin_bottom(12)
       .margin_start(12)
       .margin_end(12)
       .build();

   // ANCHOR: callback
   let (sender, receiver) = async_channel::bounded(1);
   // Connect to "clicked" signal of `button`
   button.connect_clicked(move |_| {
       RUNTIME.spawn(clone!(#[strong] sender, async move {
           let response = reqwest::get("https://www.gtk-rs.org").await;
           sender.send(response).await.expect("The channel needs to be open.");
       }));
   });

   // The main loop executes the asynchronous block
   glib::spawn_future_local(async move {
       while let Ok(response) = receiver.recv().await {
           if let Ok(response) = response {
               println!("Status: {}", response.status());
           } else {
               println!("Could not make a `GET` request.");
           }
       }
   });
   // ANCHOR_END: callback

   // Create a window
   let window = ApplicationWindow::builder()
       .application(app)
       .title("My GTK App")
       .child(&button)
       .build();

   // Present window
   window.present();
}

不幸的是，它无法编译。和往常一样，Rust 的错误信息非常有用。

cannot call non-const fn `tokio::runtime::Runtime::new` in statics
calls in statics are limited to constant functions, tuple structs and tuple variants
consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate

我们可以直接遵循建议，但标准库也提供了相应的解决方案。使用 std::sync::OnceLock 时，我们可以使用常函数 OnceLock::new() 初始化静态变量，并在函数 runtime 首次调用时初始化。

文件名：listings/main_event_loop/9/main.rs

use std::sync::OnceLock;

use glib::clone;
use gtk::glib;
use gtk::prelude::*;
use gtk::{Application, ApplicationWindow, Button};
use tokio::runtime::Runtime;

const APP_ID: &str = "org.gtk_rs.MainEventLoop9";

fn runtime() -> &'static Runtime {
    static RUNTIME: OnceLock<Runtime> = OnceLock::new();
    RUNTIME.get_or_init(|| {
        Runtime::new().expect("Setting up tokio runtime needs to succeed.")
    })
}

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    let (sender, receiver) = async_channel::bounded(1);
    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |_| {
        runtime().spawn(clone!(
            #[strong]
            sender,
            async move {
                let response = reqwest::get("https://www.gtk-rs.org").await;
                sender
                    .send(response)
                    .await
                    .expect("The channel needs to be open.");
            }
        ));
    });

    // The main loop executes the asynchronous block
    glib::spawn_future_local(async move {
        while let Ok(response) = receiver.recv().await {
            if let Ok(response) = response {
                println!("Status: {}", response.status());
            } else {
                println!("Could not make a `GET` request.");
            }
        }
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

在按钮回调中，我们现在可以使用 tokio 而不是 glib 来生成 reqwest async 代码块。

文件名：listings/main_event_loop/9/main.rs

use std::sync::OnceLock;

use glib::clone;
use gtk::glib;
use gtk::prelude::*;
use gtk::{Application, ApplicationWindow, Button};
use tokio::runtime::Runtime;

const APP_ID: &str = "org.gtk_rs.MainEventLoop9";

fn runtime() -> &'static Runtime {
    static RUNTIME: OnceLock<Runtime> = OnceLock::new();
    RUNTIME.get_or_init(|| {
        Runtime::new().expect("Setting up tokio runtime needs to succeed.")
    })
}

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    let (sender, receiver) = async_channel::bounded(1);
    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |_| {
        runtime().spawn(clone!(
            #[strong]
            sender,
            async move {
                let response = reqwest::get("https://www.gtk-rs.org").await;
                sender
                    .send(response)
                    .await
                    .expect("The channel needs to be open.");
            }
        ));
    });

    // The main loop executes the asynchronous block
    glib::spawn_future_local(async move {
        while let Ok(response) = receiver.recv().await {
            if let Ok(response) = response {
                println!("Status: {}", response.status());
            } else {
                println!("Could not make a `GET` request.");
            }
        }
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

如果我们现在按下按钮，就会在控制台中看到以下信息：

Status: 200 OK

在接下来的章节中，我们将不再需要 tokio、reqwest 或 ashpd，因此让我们再次执行删除操作：

cargo remove tokio reqwest ashpd

如何确定能否在 glib 主循环中生成async 任务？当调用的函数来自以下库时，glib 应该能够生成任务：

来自 glib 生态系统，
不依赖运行时，只依赖 futures 系列 crate (futures-io, futures-core 等等),
依赖于 async-std 或 smol 运行时，或
具有 cargo features 依赖于 async-std/smol 而不是 tokio.

结论

您不希望阻塞主线程足够长的时间，以至于用户察觉不到。但是，什么时候应该执行异步任务，而不是在单独的线程中执行任务呢？让我们再来看看不同的情况。

如果任务将时间花在计算上，而不是等待网络响应，那么它就是计算密集型(CPU-bound). 这意味着你必须在一个单独的线程中运行任务，并让它通过一个通道发送结果。

如果您的任务是IO密集型(IO bound), 那么答案取决于您可以使用的 crate 和需要完成的工作类型。

使用 glib、smol、async-std 或 futures trait 系列 crates 函数的轻量级 I/O 工作可以在主循环中启动。这样，通常就能避免通过通道进行同步。
在独立线程/异步执行器中运行繁重的 I/O 工作仍可避免主循环饱和。如果您不确定，建议进行基准测试。

如果工作的最佳 crate 依赖于 tokio，则必须使用 tokio 运行时生成它，并通过通道进行通信。

设置(Settings)

我们现在已经学会了多种处理状态的方法。但是，每次我们关闭应用程序时，它都消失了。让我们学习如何通过在 gio::Settings 中存储 Switch 的状态来使用它。

一开始，我们必须创建一个GSchema xml 文件，以描述我们的应用程序计划在设置中存储的数据类型。

文件名：listings/settings/1/org.gtk_rs.Settings1.gschema.xml

<?xml version="1.0" encoding="utf-8"?>
<schemalist>
  <schema id="org.gtk_rs.Settings1" path="/org/gtk_rs/Settings1/">
    <key name="is-switch-enabled" type="b">
      <default>false</default>
      <summary>Default switch state</summary>
    </key>
  </schema>
</schemalist>

让我们一步一步来。这个id与我们在创建应用程序时使用的应用程序 ID 相同。

文件名：listings/settings/1/main.rs

use gio::Settings;
use gtk::prelude::*;
use gtk::{gio, glib, Align, Application, ApplicationWindow, Switch};

const APP_ID: &str = "org.gtk_rs.Settings1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Initialize settings
    let settings = Settings::new(APP_ID);

    // Get the last switch state from the settings
    let is_switch_enabled = settings.boolean("is-switch-enabled");

    // Create a switch
    let switch = Switch::builder()
        .margin_top(48)
        .margin_bottom(48)
        .margin_start(48)
        .margin_end(48)
        .valign(Align::Center)
        .halign(Align::Center)
        .state(is_switch_enabled)
        .build();

    switch.connect_state_set(move |_, is_enabled| {
        // Save changed switch state in the settings
        settings
            .set_boolean("is-switch-enabled", is_enabled)
            .expect("Could not set setting.");
        // Allow to invoke other event handlers
        glib::Propagation::Proceed
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&switch)
        .build();

    // Present window
    window.present();
}

path 必须以正斜杠字符（'/'）开头和结尾，并且不能包含两个连续的斜杠字符。创建 path 时，我们建议使用id，将 '.' 替换为 '/'，并在开头和结尾添加 '/'。

我们只想存储一个name为 "is-switch-enabled" 的键。这是一个布尔值，因此其类型为 "b"（其他选项请参见 GVariant Format Strings）。我们还将其默认值设为 false（完整语法请参见 GVariant Text Format）。最后，我们添加一个摘要。

现在，我们需要复制并编译 schema.

在 Linux 或 macOS 机器上执行以下命令即可安装 schema：

mkdir -p $HOME/.local/share/glib-2.0/schemas
cp org.gtk_rs.Settings1.gschema.xml $HOME/.local/share/glib-2.0/schemas/
glib-compile-schemas $HOME/.local/share/glib-2.0/schemas/

或者在 Windows 上运行：

mkdir C:/ProgramData/glib-2.0/schemas/
cp org.gtk_rs.Settings1.gschema.xml C:/ProgramData/glib-2.0/schemas/
glib-compile-schemas C:/ProgramData/glib-2.0/schemas/

我们通过指定应用程序 ID 来初始化 Settings 对象。

文件名：listings/settings/1/main.rs

use gio::Settings;
use gtk::prelude::*;
use gtk::{gio, glib, Align, Application, ApplicationWindow, Switch};

const APP_ID: &str = "org.gtk_rs.Settings1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Initialize settings
    let settings = Settings::new(APP_ID);

    // Get the last switch state from the settings
    let is_switch_enabled = settings.boolean("is-switch-enabled");

    // Create a switch
    let switch = Switch::builder()
        .margin_top(48)
        .margin_bottom(48)
        .margin_start(48)
        .margin_end(48)
        .valign(Align::Center)
        .halign(Align::Center)
        .state(is_switch_enabled)
        .build();

    switch.connect_state_set(move |_, is_enabled| {
        // Save changed switch state in the settings
        settings
            .set_boolean("is-switch-enabled", is_enabled)
            .expect("Could not set setting.");
        // Allow to invoke other event handlers
        glib::Propagation::Proceed
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&switch)
        .build();

    // Present window
    window.present();
}

然后我们获取设置密钥，并在创建 Switch 时使用它。

文件名：listings/settings/1/main.rs

use gio::Settings;
use gtk::prelude::*;
use gtk::{gio, glib, Align, Application, ApplicationWindow, Switch};

const APP_ID: &str = "org.gtk_rs.Settings1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Initialize settings
    let settings = Settings::new(APP_ID);

    // Get the last switch state from the settings
    let is_switch_enabled = settings.boolean("is-switch-enabled");

    // Create a switch
    let switch = Switch::builder()
        .margin_top(48)
        .margin_bottom(48)
        .margin_start(48)
        .margin_end(48)
        .valign(Align::Center)
        .halign(Align::Center)
        .state(is_switch_enabled)
        .build();

    switch.connect_state_set(move |_, is_enabled| {
        // Save changed switch state in the settings
        settings
            .set_boolean("is-switch-enabled", is_enabled)
            .expect("Could not set setting.");
        // Allow to invoke other event handlers
        glib::Propagation::Proceed
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&switch)
        .build();

    // Present window
    window.present();
}

最后，我们保证，只要点击开关，开关状态就会保存在设置中。

文件名：listings/settings/1/main.rs

use gio::Settings;
use gtk::prelude::*;
use gtk::{gio, glib, Align, Application, ApplicationWindow, Switch};

const APP_ID: &str = "org.gtk_rs.Settings1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Initialize settings
    let settings = Settings::new(APP_ID);

    // Get the last switch state from the settings
    let is_switch_enabled = settings.boolean("is-switch-enabled");

    // Create a switch
    let switch = Switch::builder()
        .margin_top(48)
        .margin_bottom(48)
        .margin_start(48)
        .margin_end(48)
        .valign(Align::Center)
        .halign(Align::Center)
        .state(is_switch_enabled)
        .build();

    switch.connect_state_set(move |_, is_enabled| {
        // Save changed switch state in the settings
        settings
            .set_boolean("is-switch-enabled", is_enabled)
            .expect("Could not set setting.");
        // Allow to invoke other event handlers
        glib::Propagation::Proceed
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&switch)
        .build();

    // Present window
    window.present();
}

现在，即使关闭应用程序，Switch 也会保留其状态。但我们可以做得更好。开关有一个属性 "active"，而 Settings 允许我们将属性与特定设置绑定。因此，我们就来做这件事。

我们可以删除初始化 Switch 之前的 boolean 调用以及 connect_state_set 调用。然后，我们通过指定键、对象和属性名称将设置绑定到属性。

文件名：listings/settings/2/main.rs

use gio::Settings;
use gtk::prelude::*;
use gtk::{gio, glib, Align, Application, ApplicationWindow, Switch};

const APP_ID: &str = "org.gtk_rs.Settings2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Initialize settings
    let settings = Settings::new(APP_ID);

    // Create a switch
    let switch = Switch::builder()
        .margin_top(48)
        .margin_bottom(48)
        .margin_start(48)
        .margin_end(48)
        .valign(Align::Center)
        .halign(Align::Center)
        .build();

    settings
        .bind("is-switch-enabled", &switch, "active")
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&switch)
        .build();

    // Present window
    window.present();
}

只要有一个属性与一个设置很好地对应，你可能就会想把它绑定到设置上。在其他情况下，通过 getter 和 setter 方法与设置交互往往是正确的选择。

保存窗口状态

很多时候，我们希望窗口状态在会话之间持续存在。如果用户调整窗口大小或将其最大化，他们可能会希望下次打开应用程序时，窗口仍保持同样的状态。 GTK 并没有提供这种功能，但幸运的是，手动实现它并不难。我们基本上需要两个整数(高度 height 和宽度 width) 和一个布尔值（is_maximized）来持久化。我们已经知道如何通过使用 gio::Settings 来做到这一点。

文件名：listings/saving_window_state/1/org.gtk_rs.SavingWindowState1.gschema.xml

<?xml version="1.0" encoding="utf-8"?>
<schemalist>
  <schema id="org.gtk_rs.SavingWindowState1" path="/org/gtk_rs/SavingWindowState1/">
    <key name="window-width" type="i">
      <default>-1</default>
      <summary>Default window width</summary>
    </key>
    <key name="window-height" type="i">
      <default>-1</default>
      <summary>Default window height</summary>
    </key>
    <key name="is-maximized" type="b">
      <default>false</default>
      <summary>Default window maximized behaviour</summary>
    </key>
  </schema>
</schemalist>

由于我们不关心中间状态，因此只在构建窗口时加载窗口状态，并在关闭窗口时保存窗口状态。这可以通过创建自定义窗口来实现。首先，我们创建一个窗口，并添加用于访问设置和窗口状态的便捷方法。

文件名：listings/saving_window_state/1/custom_window/mod.rs

mod imp;

use gio::Settings;
use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application};

use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    pub fn save_window_size(&self) -> Result<(), glib::BoolError> {
        // Get the size of the window
        let size = self.default_size();

        // Set the window state in `settings`
        self.settings().set_int("window-width", size.0)?;
        self.settings().set_int("window-height", size.1)?;
        self.settings()
            .set_boolean("is-maximized", self.is_maximized())?;

        Ok(())
    }

    fn load_window_size(&self) {
        // Get the window state from `settings`
        let width = self.settings().int("window-width");
        let height = self.settings().int("window-height");
        let is_maximized = self.settings().boolean("is-maximized");

        // Set the size of the window
        self.set_default_size(width, height);

        // If the window was maximized when it was closed, maximize it again
        if is_maximized {
            self.maximize();
        }
    }
}

我们通过将 "application" 属性传递给 glib::Object::new 来设置该属性。您甚至可以用这种方法设置多个属性。在创建新的 GObject 时，这比手动调用 setter 方法要好得多。

实现的结构包含 settings. 您可以看到，我们将 settings 嵌入到 std::cell::OnceCell 中。当你知道只需初始化一次值时，这是 RefCell<Option<T>> 的一个很好的替代方法。我们还重写了 constructed 和 close_request 方法，通过它们来加载或保存窗口状态。

文件名：listings/saving_window_state/1/custom_window/imp.rs

use gio::Settings;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, ApplicationWindow};
use std::cell::OnceCell;

#[derive(Default)]
pub struct Window {
    pub settings: OnceCell<Settings>,
}

#[glib::object_subclass]
impl ObjectSubclass for Window {
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = ApplicationWindow;
}
impl ObjectImpl for Window {
    fn constructed(&self) {
        self.parent_constructed();
        // Load latest window state
        let obj = self.obj();
        obj.setup_settings();
        obj.load_window_size();
    }
}
impl WidgetImpl for Window {}
impl WindowImpl for Window {
    // Save window state right before the window will be closed
    fn close_request(&self) -> glib::Propagation {
        // Save window size
        self.obj()
            .save_window_size()
            .expect("Failed to save window state");
        // Allow to invoke other event handlers
        glib::Propagation::Proceed
    }
}
impl ApplicationWindowImpl for Window {}

就是这样！现在，我们的窗口可以在应用程序会话之间保持状态。

列表控件

有时，您想以某种排列方式显示元素列表。gtk::ListBox 和 gtk::FlowBox 是两个容器部件，可以让您做到这一点。 ListBox 是垂直列表，而 FlowBox 是网格。

让我们通过在 ListBox 中添加标签来探索这一概念。标签将显示从 0 到 100 的整数。

文件名：listings/list_widgets/1/main.rs

use gtk::prelude::*;
use gtk::{
    glib, Application, ApplicationWindow, Label, ListBox, PolicyType, ScrolledWindow,
};

const APP_ID: &str = "org.gtk_rs.ListWidgets1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `ListBox` and add labels with integers from 0 to 100
    let list_box = ListBox::new();
    for number in 0..=100 {
        let label = Label::new(Some(&number.to_string()));
        list_box.append(&label);
    }

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_box)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

我们不能同时显示这么多部件。因此，我们将 ListBox 添加到 gtk::ScrolledWindow 中。现在我们可以滚动浏览我们的元素了。

文件名：listings/list_widgets/1/main.rs

use gtk::prelude::*;
use gtk::{
    glib, Application, ApplicationWindow, Label, ListBox, PolicyType, ScrolledWindow,
};

const APP_ID: &str = "org.gtk_rs.ListWidgets1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `ListBox` and add labels with integers from 0 to 100
    let list_box = ListBox::new();
    for number in 0..=100 {
        let label = Label::new(Some(&number.to_string()));
        list_box.append(&label);
    }

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_box)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

Views

这很简单。不过，目前我们为每个元素创建一个小部件。由于每个窗口小部件都会占用一些资源，因此很多窗口小部件会导致用户界面反应变慢。根据部件类型的不同，即使有成千上万个元素也可能不是问题。但是，我们怎么可能处理社交媒体时间线中无数的帖子呢？

我们改用可扩展列表！

**模型(model)**保存我们的数据，对其进行过滤并描述其顺序。
**列表项工厂(list item factory)**定义了数据如何转换为控件。
**视图(view)**指定控件的排列方式。

使这一概念具有可扩展性的是，GTK 只需创建略多于我们目前所能看到的控件。当我们滚动浏览元素时，不可见的控件将被重复使用。下图演示了实际操作过程。

Diagram showing how list widgets are being recycled

100000 个元素是 ListBox 难以承受的，因此让我们用它来演示可扩展列表。

我们首先定义并填充模型。该模型是 gio::ListStore 的一个实例。这里的主要限制是 gio::ListStore 只接受 GObject. 因此，让我们创建一个用数字初始化的自定义 GObject IntegerObject.

文件名：listings/list_widgets/2/integer_object/mod.rs

mod imp;

use glib::Object;
use gtk::glib;

glib::wrapper! {
    pub struct IntegerObject(ObjectSubclass<imp::IntegerObject>);
}

impl IntegerObject {
    pub fn new(number: i32) -> Self {
        Object::builder().property("number", number).build()
    }
}

number 代表 IntegerObject 的内部状态。

文件名：listings/list_widgets/2/integer_object/imp.rs

use std::cell::Cell;

use glib::Properties;
use gtk::glib;
use gtk::prelude::*;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Properties, Default)]
#[properties(wrapper_type = super::IntegerObject)]
pub struct IntegerObject {
    #[property(get, set)]
    number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for IntegerObject {
    const NAME: &'static str = "MyGtkAppIntegerObject";
    type Type = super::IntegerObject;
}

// Trait shared by all GObjects
#[glib::derived_properties]
impl ObjectImpl for IntegerObject {}

现在我们用 0 到 100000 的整数填充模型。请注意，模型只处理数据。这里没有提及标签或任何其他控件。

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, Label, ListView, PolicyType,
    ScrolledWindow, SignalListItemFactory, SingleSelection,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        let label = Label::new(None);
        list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .set_child(Some(&label));
    });

    factory.connect_bind(move |_, list_item| {
        // Get `IntegerObject` from `ListItem`
        let integer_object = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .item()
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Get `Label` from `ListItem`
        let label = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .child()
            .and_downcast::<Label>()
            .expect("The child has to be a `Label`.");

        // Set "label" to "number"
        label.set_label(&integer_object.number().to_string());
    });

    let selection_model = SingleSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

ListItemFactory 负责处理控件及其与模型的关系。在这里，我们使用了 SignalListItemFactory ，它可以为 ListItem 生命周期中的每一个相关步骤发出一个信号。当需要创建新的部件时，"setup"（设置）信号就会发出。我们连接到该信号，为每个请求的部件创建一个标签。

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, Label, ListView, PolicyType,
    ScrolledWindow, SignalListItemFactory, SingleSelection,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        let label = Label::new(None);
        list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .set_child(Some(&label));
    });

    factory.connect_bind(move |_, list_item| {
        // Get `IntegerObject` from `ListItem`
        let integer_object = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .item()
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Get `Label` from `ListItem`
        let label = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .child()
            .and_downcast::<Label>()
            .expect("The child has to be a `Label`.");

        // Set "label" to "number"
        label.set_label(&integer_object.number().to_string());
    });

    let selection_model = SingleSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

在“绑定”步骤中，我们将模型中的数据绑定到各个列表项。

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, Label, ListView, PolicyType,
    ScrolledWindow, SignalListItemFactory, SingleSelection,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        let label = Label::new(None);
        list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .set_child(Some(&label));
    });

    factory.connect_bind(move |_, list_item| {
        // Get `IntegerObject` from `ListItem`
        let integer_object = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .item()
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Get `Label` from `ListItem`
        let label = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .child()
            .and_downcast::<Label>()
            .expect("The child has to be a `Label`.");

        // Set "label" to "number"
        label.set_label(&integer_object.number().to_string());
    });

    let selection_model = SingleSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

我们只希望单个项目可选，因此选择了 SingleSelection。其他选项是多选（MultiSelection）和不选（NoSelection）。然后，我们将模型和工厂传递给 ListView。

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, Label, ListView, PolicyType,
    ScrolledWindow, SignalListItemFactory, SingleSelection,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        let label = Label::new(None);
        list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .set_child(Some(&label));
    });

    factory.connect_bind(move |_, list_item| {
        // Get `IntegerObject` from `ListItem`
        let integer_object = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .item()
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Get `Label` from `ListItem`
        let label = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .child()
            .and_downcast::<Label>()
            .expect("The child has to be a `Label`.");

        // Set "label" to "number"
        label.set_label(&integer_object.number().to_string());
    });

    let selection_model = SingleSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

每个 ListView 都必须是 ScrolledWindow 的直接子窗口，因此我们要将其添加到 ScrolledWindow 中。

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, Label, ListView, PolicyType,
    ScrolledWindow, SignalListItemFactory, SingleSelection,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        let label = Label::new(None);
        list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .set_child(Some(&label));
    });

    factory.connect_bind(move |_, list_item| {
        // Get `IntegerObject` from `ListItem`
        let integer_object = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .item()
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Get `Label` from `ListItem`
        let label = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .child()
            .and_downcast::<Label>()
            .expect("The child has to be a `Label`.");

        // Set "label" to "number"
        label.set_label(&integer_object.number().to_string());
    });

    let selection_model = SingleSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

现在，我们可以轻松地滚动浏览一长串整数。

让我们看看还能做些什么。我们可能想在每次激活行时增加数字。为此，我们首先要为 IntegerObject 添加 increase_number 方法。

文件名：listings/list_widgets/3/integer_object/mod.rs

mod imp;

use glib::Object;
use gtk::glib;

glib::wrapper! {
    pub struct IntegerObject(ObjectSubclass<imp::IntegerObject>);
}

impl IntegerObject {
    pub fn new(number: i32) -> Self {
        Object::builder().property("number", number).build()
    }

    pub fn increase_number(self) {
        self.set_number(self.number() + 1);
    }
}

为了与 ListView 交互，我们要连接到它的 "激活(activate)" 信号。

文件名：listings/list_widgets/3/main.rs

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, Label, ListView, PolicyType,
    ScrolledWindow, SignalListItemFactory, SingleSelection,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        let label = Label::new(None);
        list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .set_child(Some(&label));
    });

    factory.connect_bind(move |_, list_item| {
        // Get `IntegerObject` from `ListItem`
        let integer_object = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .item()
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Get `Label` from `ListItem`
        let label = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .child()
            .and_downcast::<Label>()
            .expect("The child has to be a `Label`.");

        // Bind "label" to "number"
        integer_object
            .bind_property("number", &label, "label")
            .sync_create()
            .build();
    });

    let selection_model = SingleSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    list_view.connect_activate(move |list_view, position| {
        // Get `IntegerObject` from model
        let model = list_view.model().expect("The model has to exist.");
        let integer_object = model
            .item(position)
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Increase "number" of `IntegerObject`
        integer_object.increase_number();
    });

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

现在，每当我们激活一个元素，例如双击该元素，模型中 IntegerObject 对应的 "数字(number)" 属性就会增加 1. 然而，IntegerObject 被修改后，对应的 Label 并不会立即改变。一种简单的方法是在 SignalListItemFactory 的 "绑定(bind)"步骤中绑定属性。

文件名：listings/list_widgets/3/main.rs

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, Label, ListView, PolicyType,
    ScrolledWindow, SignalListItemFactory, SingleSelection,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        let label = Label::new(None);
        list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .set_child(Some(&label));
    });

    factory.connect_bind(move |_, list_item| {
        // Get `IntegerObject` from `ListItem`
        let integer_object = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .item()
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Get `Label` from `ListItem`
        let label = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem")
            .child()
            .and_downcast::<Label>()
            .expect("The child has to be a `Label`.");

        // Bind "label" to "number"
        integer_object
            .bind_property("number", &label, "label")
            .sync_create()
            .build();
    });

    let selection_model = SingleSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    list_view.connect_activate(move |list_view, position| {
        // Get `IntegerObject` from model
        let model = list_view.model().expect("The model has to exist.");
        let integer_object = model
            .item(position)
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Increase "number" of `IntegerObject`
        integer_object.increase_number();
    });

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

乍一看，这似乎可行。但是，当你滚动并激活几个列表元素时，你会发现有时多个数字会发生变化，即使你只激活了一个。这与视图的内部工作方式有关。并不是每个模型项都属于一个部件，而是随着视图的滚动，部件会被循环使用。这也意味着，在我们的例子中，多个数字将绑定到同一个部件上。

表达式(Expressions)

类似这样的情况非常常见，因此 GTK 提供了一种属性绑定的替代方法：表达式(Expression)。作为第一步，它允许我们删除 "绑定(bind)" 步骤。让我们看看 "设置(setup)" 步骤现在是如何工作的。

文件名：listings/list_widgets/4/main.rs

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, Label, ListView, PolicyType,
    ScrolledWindow, SignalListItemFactory, SingleSelection, Widget,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets4";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        // Create label
        let label = Label::new(None);
        let list_item = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem");
        list_item.set_child(Some(&label));

        // Bind `list_item->item->number` to `label->label`
        list_item
            .property_expression("item")
            .chain_property::<IntegerObject>("number")
            .bind(&label, "label", Widget::NONE);
    });

    let selection_model = SingleSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    list_view.connect_activate(move |list_view, position| {
        // Get `IntegerObject` from model
        let model = list_view.model().expect("The model has to exist.");
        let integer_object = model
            .item(position)
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Increase "number" of `IntegerObject`
        integer_object.increase_number();
    });

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

表达式提供了一种描述值引用的方法。有趣的是，这些引用可以是几步之外的。这样，在上面的代码段中，我们就可以将 list_item 的属性 "item" 的 "number" 属性与标签的 "label" 属性绑定。

值得注意的是，在 "设置(setup)" 阶段，我们无法知道哪个列表项属于哪个标签，因为当我们滚动列表时，这一点会发生变化。在这里，表达式的另一个功能就显现出来了。表达式允许我们描述对象或属性之间的关系，而这些关系可能还不存在。我们只需告诉它，只要属于它的数字发生变化，就必须更改标签。这样，我们也不会遇到多个标签绑定到同一个数字上的问题。现在，当我们激活一个标签时，只有相应的数字会发生可见的变化。

让我们进一步扩展应用程序。例如，我们可以过滤我们的模型，使其只允许偶数。为此，我们可以将其与 gtk::CustomFilter 一起传递给 gtk::FilterListModel .

文件名：listings/list_widgets/5/main.rs

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, CustomFilter, CustomSorter,
    FilterChange, FilterListModel, Label, ListView, PolicyType, ScrolledWindow,
    SignalListItemFactory, SingleSelection, SortListModel, SorterChange, Widget,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets5";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        // Create label
        let label = Label::new(None);
        let list_item = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem");
        list_item.set_child(Some(&label));

        // Bind `list_item->item->number` to `label->label`
        list_item
            .property_expression("item")
            .chain_property::<IntegerObject>("number")
            .bind(&label, "label", Widget::NONE);
    });

    let filter = CustomFilter::new(move |obj| {
        // Get `IntegerObject` from `glib::Object`
        let integer_object = obj
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");

        // Only allow even numbers
        integer_object.number() % 2 == 0
    });
    let filter_model = FilterListModel::new(Some(model), Some(filter.clone()));

    let sorter = CustomSorter::new(move |obj1, obj2| {
        // Get `IntegerObject` from `glib::Object`
        let integer_object_1 = obj1
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");
        let integer_object_2 = obj2
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");

        // Get property "number" from `IntegerObject`
        let number_1 = integer_object_1.number();
        let number_2 = integer_object_2.number();

        // Reverse sorting order -> large numbers come first
        number_2.cmp(&number_1).into()
    });
    let sort_model = SortListModel::new(Some(filter_model), Some(sorter.clone()));

    let selection_model = SingleSelection::new(Some(sort_model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    list_view.connect_activate(move |list_view, position| {
        // Get `IntegerObject` from model
        let model = list_view.model().expect("The model has to exist.");
        let integer_object = model
            .item(position)
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Increase "number" of `IntegerObject`
        integer_object.increase_number();

        // Notify that the filter and sorter have been changed
        filter.changed(FilterChange::Different);
        sorter.changed(SorterChange::Different);
    });

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

此外，我们还可以颠倒模型的顺序。现在，我们将过滤后的模型与 gtk::CustomSorter 一起传递给 gtk::SortListModel.

文件名：listings/list_widgets/5/main.rs

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, CustomFilter, CustomSorter,
    FilterChange, FilterListModel, Label, ListView, PolicyType, ScrolledWindow,
    SignalListItemFactory, SingleSelection, SortListModel, SorterChange, Widget,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets5";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        // Create label
        let label = Label::new(None);
        let list_item = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem");
        list_item.set_child(Some(&label));

        // Bind `list_item->item->number` to `label->label`
        list_item
            .property_expression("item")
            .chain_property::<IntegerObject>("number")
            .bind(&label, "label", Widget::NONE);
    });

    let filter = CustomFilter::new(move |obj| {
        // Get `IntegerObject` from `glib::Object`
        let integer_object = obj
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");

        // Only allow even numbers
        integer_object.number() % 2 == 0
    });
    let filter_model = FilterListModel::new(Some(model), Some(filter.clone()));

    let sorter = CustomSorter::new(move |obj1, obj2| {
        // Get `IntegerObject` from `glib::Object`
        let integer_object_1 = obj1
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");
        let integer_object_2 = obj2
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");

        // Get property "number" from `IntegerObject`
        let number_1 = integer_object_1.number();
        let number_2 = integer_object_2.number();

        // Reverse sorting order -> large numbers come first
        number_2.cmp(&number_1).into()
    });
    let sort_model = SortListModel::new(Some(filter_model), Some(sorter.clone()));

    let selection_model = SingleSelection::new(Some(sort_model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    list_view.connect_activate(move |list_view, position| {
        // Get `IntegerObject` from model
        let model = list_view.model().expect("The model has to exist.");
        let integer_object = model
            .item(position)
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Increase "number" of `IntegerObject`
        integer_object.increase_number();

        // Notify that the filter and sorter have been changed
        filter.changed(FilterChange::Different);
        sorter.changed(SorterChange::Different);
    });

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

为了确保在修改数字时，我们的过滤器和排序器能得到更新，我们调用了它们的 changed 方法。

文件名：listings/list_widgets/5/main.rs

mod integer_object;

use gtk::{
    gio, glib, Application, ApplicationWindow, CustomFilter, CustomSorter,
    FilterChange, FilterListModel, Label, ListView, PolicyType, ScrolledWindow,
    SignalListItemFactory, SingleSelection, SortListModel, SorterChange, Widget,
};
use gtk::{prelude::*, ListItem};
use integer_object::IntegerObject;

const APP_ID: &str = "org.gtk_rs.ListWidgets5";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `Vec<IntegerObject>` with numbers from 0 to 100_000
    let vector: Vec<IntegerObject> = (0..=100_000).map(IntegerObject::new).collect();

    // Create new model
    let model = gio::ListStore::new::<IntegerObject>();

    // Add the vector to the model
    model.extend_from_slice(&vector);

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        // Create label
        let label = Label::new(None);
        let list_item = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem");
        list_item.set_child(Some(&label));

        // Bind `list_item->item->number` to `label->label`
        list_item
            .property_expression("item")
            .chain_property::<IntegerObject>("number")
            .bind(&label, "label", Widget::NONE);
    });

    let filter = CustomFilter::new(move |obj| {
        // Get `IntegerObject` from `glib::Object`
        let integer_object = obj
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");

        // Only allow even numbers
        integer_object.number() % 2 == 0
    });
    let filter_model = FilterListModel::new(Some(model), Some(filter.clone()));

    let sorter = CustomSorter::new(move |obj1, obj2| {
        // Get `IntegerObject` from `glib::Object`
        let integer_object_1 = obj1
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");
        let integer_object_2 = obj2
            .downcast_ref::<IntegerObject>()
            .expect("The object needs to be of type `IntegerObject`.");

        // Get property "number" from `IntegerObject`
        let number_1 = integer_object_1.number();
        let number_2 = integer_object_2.number();

        // Reverse sorting order -> large numbers come first
        number_2.cmp(&number_1).into()
    });
    let sort_model = SortListModel::new(Some(filter_model), Some(sorter.clone()));

    let selection_model = SingleSelection::new(Some(sort_model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    list_view.connect_activate(move |list_view, position| {
        // Get `IntegerObject` from model
        let model = list_view.model().expect("The model has to exist.");
        let integer_object = model
            .item(position)
            .and_downcast::<IntegerObject>()
            .expect("The item has to be an `IntegerObject`.");

        // Increase "number" of `IntegerObject`
        integer_object.increase_number();

        // Notify that the filter and sorter have been changed
        filter.changed(FilterChange::Different);
        sorter.changed(SorterChange::Different);
    });

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

更改后，应用程序看起来就像这样：

Window with a list of 100 000 integers, starting from 100 000

字符串列表

通常情况下，您只想显示一个字符串列表。但是，如果您需要对显示的数据进行过滤和排序，或者元素太多，无法用 ListBox 显示，您仍然需要使用视图。 GTK 为这种情况提供了一个方便的模型： gtk::StringList.

让我们通过一个小例子来看看如何使用这个 API。过滤器和排序器由工厂控制，所以这里没有什么变化。

首先，我们向模型中添加一系列字符串。

文件名：listings/list_widgets/6/main.rs

use gtk::{glib, prelude::*, ListItem};
use gtk::{
    Application, ApplicationWindow, Label, ListView, NoSelection, PolicyType,
    ScrolledWindow, SignalListItemFactory, StringList, StringObject, Widget,
};

const APP_ID: &str = "org.gtk_rs.ListWidgets6";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `StringList` with number from 0 to 100_000
    // `StringList` implements FromIterator<String>
    let model: StringList = (0..=100_000).map(|number| number.to_string()).collect();

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        // Create label
        let label = Label::new(None);
        let list_item = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem");
        list_item.set_child(Some(&label));

        // Bind `list_item->item->string` to `label->label`
        list_item
            .property_expression("item")
            .chain_property::<StringObject>("string")
            .bind(&label, "label", Widget::NONE);
    });

    let selection_model = NoSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

请注意，我们可以直接从字符串的迭代器中创建一个 StringList. 这意味着我们不必再为我们的模型创建一个自定义的 GObject.

像往常一样，我们通过表达式将标签与列表项连接起来。在这里，我们可以使用 StringObject, 它可以通过属性 "string"显示内容。

文件名：listings/list_widgets/6/main.rs

use gtk::{glib, prelude::*, ListItem};
use gtk::{
    Application, ApplicationWindow, Label, ListView, NoSelection, PolicyType,
    ScrolledWindow, SignalListItemFactory, StringList, StringObject, Widget,
};

const APP_ID: &str = "org.gtk_rs.ListWidgets6";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a `StringList` with number from 0 to 100_000
    // `StringList` implements FromIterator<String>
    let model: StringList = (0..=100_000).map(|number| number.to_string()).collect();

    let factory = SignalListItemFactory::new();
    factory.connect_setup(move |_, list_item| {
        // Create label
        let label = Label::new(None);
        let list_item = list_item
            .downcast_ref::<ListItem>()
            .expect("Needs to be ListItem");
        list_item.set_child(Some(&label));

        // Bind `list_item->item->string` to `label->label`
        list_item
            .property_expression("item")
            .chain_property::<StringObject>("string")
            .bind(&label, "label", Widget::NONE);
    });

    let selection_model = NoSelection::new(Some(model));
    let list_view = ListView::new(Some(selection_model), Some(factory));

    let scrolled_window = ScrolledWindow::builder()
        .hscrollbar_policy(PolicyType::Never) // Disable horizontal scrolling
        .min_content_width(360)
        .child(&list_view)
        .build();

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .default_width(600)
        .default_height(300)
        .child(&scrolled_window)
        .build();

    // Present window
    window.present();
}

结论

我们现在知道了如何显示数据列表。少量元素可由 ListBox 或 FlowBox 处理。这些窗口小部件使用方便，必要时还可以绑定到 gio::ListStore 等模型上。这样就可以更方便地修改、排序和过滤数据。但是，如果我们需要这些部件具有可扩展性，我们仍然需要使用 ListView, ColumnView 或 GridView.

复合模板

在此之前，每当我们构建预定义的部件时，我们都依赖于构建器模式。提醒一下，我们就是这样使用它来构建我们值得信赖的 "Hello World!

use gtk::prelude::*;
use gtk::{glib, Application, ApplicationWindow, Button};
const APP_ID: &str = "org.gtk_rs.HelloWorld3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a button with label and margins
    let button = Button::builder()
        .label("Press me!")
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(|button| {
        // Set the label to "Hello World!" after the button has been clicked on
        button.set_label("Hello World!");
    });

    // Create a window
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .child(&button)
        .build();

    // Present window
    window.present();
}

直接从代码中创建小部件固然很好，但却很难将逻辑与用户界面分离开来。这就是为什么大多数工具包都允许使用标记语言来描述用户界面，GTK 也不例外。例如，下面的 `xml` 文件描述了 “Hello World!” 应用。

文件名：listings/composite_templates/1/resources/window.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="MyGtkAppWindow" parent="GtkApplicationWindow">
    <property name="title">My GTK App</property>
    <child>
      <object class="GtkButton" id="button">
        <property name="label">Press me!</property>
        <property name="margin-top">12</property>
        <property name="margin-bottom">12</property>
        <property name="margin-start">12</property>
        <property name="margin-end">12</property>  
      </object>
    </child>
  </template>
</interface>

最外层的标签必须是 <interface> （接口）。然后开始列出要描述的元素。为了定义一个复合模板，我们指定了要创建的自定义控件的名称 MyGtkAppWindow 及其派生自的父级 gtk::ApplicationWindow. 这些 xml 文件与编程语言无关，这也是为什么这些类使用原始名称的原因。幸运的是，它们都是这样转换的：gtk::ApplicationWindow → GtkApplicationWindow. 然后我们就可以为 ApplicationWindow 指定属性了（在这里给出）。由于 ApplicationWindow 可以包含其他控件，我们使用 <child> 标记来添加一个 gtk::Button. 我们希望以后能引用该按钮，因此还设置了它的 id.

Resources（资源）

为了将模板文件嵌入应用程序，我们使用了 gio::Resource. 要嵌入的文件同样由 xml 文件描述。我们还为模板文件添加了压缩(compressed)和预处理(preprocess)属性，以减小资源的最终大小。

文件名：listings/composite_templates/1/resources/resources.gresource.xml

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/org/gtk_rs/example/">
    <file compressed="true" preprocess="xml-stripblanks">window.ui</file>
  </gresource>
</gresources>

现在，我们必须编译资源并将其链接到应用程序。一种方法是在 cargo 编译脚本中执行 glib_build_tools::compile_resources.

首先，我们必须在 Cargo.toml 中添加 glib-build-tools 作为编译依赖，方法是执行：

cargo add glib-build-tools --build

然后，我们在软件包根目录下创建一个 build.rs，内容如下。每当我们使用 cargo 触发编译时，它就会对资源进行编译，然后静态链接我们的可执行文件。

文件名：listings/build.rs

fn main() {
    glib_build_tools::compile_resources(
        &["composite_templates/1/resources"],
        "composite_templates/1/resources/resources.gresource.xml",
        "composite_templates_1.gresource",
    );
}

最后，我们通过调用宏 gio::resources_register_include! 来注册并包含资源。在您自己的应用程序中，请注意在创建 gtk::Application 之前注册资源。

文件名：listings/composite_templates/1/main.rs

mod window;

use gtk::prelude::*;
use gtk::{gio, glib, Application};
use window::Window;

const APP_ID: &str = "org.gtk_rs.CompositeTemplates1";

fn main() -> glib::ExitCode {
    // Register and include resources
    gio::resources_register_include!("composite_templates_1.gresource")
        .expect("Failed to register resources.");

    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}
fn build_ui(app: &Application) {
    // Create new window and present it
    let window = Window::new(app);
    window.present();
}

在我们的代码中，我们创建了一个继承自 gtk::ApplicationWindow 的自定义控件，以使用我们的模板。文件名：listings/composite_templates/1/window/mod.rs

mod imp;

use glib::Object;
use gtk::{gio, glib, Application};

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }
}

在实现结构中，我们添加了派生宏 gtk::CompositeTemplate. 我们还指定模板信息来自前缀为 /org/gtk-rs/example 的资源，其中包含 window.ui 文件。

模板的一个非常方便的功能是模板子结构。使用方法是在模板中添加一个与 id 属性同名的结构成员。然后，TemplateChild 会存储一个控件的引用，供以后使用。稍后，当我们要为按钮添加回调时，这将非常有用。

文件名：listings/composite_templates/1/window/imp.rs

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, Button, CompositeTemplate};

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub button: TemplateChild<Button>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Connect to "clicked" signal of `button`
        self.button.connect_clicked(move |button| {
            // Set the label to "Hello World!" after the button has been clicked on
            button.set_label("Hello World!");
        });
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

在 ObjectSubclass trait 中，我们确保 NAME 与模板中的类相对应，ParentType 与模板中的父类相对应。我们还在 class_init 和 instance_init 中绑定并初始化模板。

文件名：listings/composite_templates/1/window/imp.rs

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, Button, CompositeTemplate};

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub button: TemplateChild<Button>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Connect to "clicked" signal of `button`
        self.button.connect_clicked(move |button| {
            // Set the label to "Hello World!" after the button has been clicked on
            button.set_label("Hello World!");
        });
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

最后，我们将回调连接到构造函数(constructed)中按钮(button)的 "clicked" 信号。由于在 self 中存储了引用，所以按钮很容易就能找到。

文件名：listings/composite_templates/1/window/imp.rs

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, Button, CompositeTemplate};

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub button: TemplateChild<Button>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Connect to "clicked" signal of `button`
        self.button.connect_clicked(move |button| {
            // Set the label to "Hello World!" after the button has been clicked on
            button.set_label("Hello World!");
        });
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

自定义控件

我们还可以在模板文件中实例化自定义控件。首先我们定义 CustomButton，它继承于 gtk::Button. 像往常一样，我们在 imp.rs 中定义实现结构。请注意我们在这里定义的 NAME，稍后我们将需要它在模板中进行引用。

文件名：listings/composite_templates/2/custom_button/imp.rs

use gtk::glib;
use gtk::subclass::prelude::*;

// Object holding the state
#[derive(Default)]
pub struct CustomButton;

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for CustomButton {
    const NAME: &'static str = "MyGtkAppCustomButton";
    type Type = super::CustomButton;
    type ParentType = gtk::Button;
}

// Trait shared by all GObjects
impl ObjectImpl for CustomButton {}

// Trait shared by all widgets
impl WidgetImpl for CustomButton {}

// Trait shared by all buttons
impl ButtonImpl for CustomButton {}

我们还在 mod.rs 中定义了公共结构。

文件名：listings/composite_templates/2/custom_button/mod.rs

use glib::Object;
use gtk::glib;

mod imp;

glib::wrapper! {
    pub struct CustomButton(ObjectSubclass<imp::CustomButton>)
        @extends gtk::Button, gtk::Widget,
        @implements gtk::Accessible, gtk::Actionable,
                    gtk::Buildable, gtk::ConstraintTarget;
}

impl CustomButton {
    pub fn new() -> Self {
        Object::builder().build()
    }
}

impl Default for CustomButton {
    fn default() -> Self {
        Self::new()
    }
}

由于我们现在要引用 CustomButton，因此还必须将模板子代的类型更改为 CustomButton。

文件名：listings/composite_templates/2/window/imp.rs

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, CompositeTemplate};

use crate::custom_button::CustomButton;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub button: TemplateChild<CustomButton>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Connect to "clicked" signal of `button`
        self.button.connect_clicked(move |button| {
            // Set the label to "Hello World!" after the button has been clicked on
            button.set_label("Hello World!");
        });
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

最后，我们可以在复合模板中用 MyGtkAppCustomButton 替换 GtkButton。由于自定义按钮是 gtk::Button 的直接子类，并且没有做任何修改，因此我们应用程序的行为将保持不变。

文件名：listings/composite_templates/2/resources/window.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="MyGtkAppWindow" parent="GtkApplicationWindow">
    <property name="title">My GTK App</property>
    <child>
      <object class="MyGtkAppCustomButton" id="button">
        <property name="label">Press me!</property>
        <property name="margin-top">12</property>
        <property name="margin-bottom">12</property>
        <property name="margin-start">12</property>
        <property name="margin-end">12</property>  
      </object>
    </child>
  </template>
</interface>

Template Callbacks

我们甚至可以在复合模板中指定信号的处理程序。这可以通过 <signal> 标记来实现，该标记包含信号名称和 Rust 代码中的处理程序。

文件名：listings/composite_templates/3/resources/window.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="MyGtkAppWindow" parent="GtkApplicationWindow">
    <property name="title">My GTK App</property>
    <child>
      <object class="MyGtkAppCustomButton" id="button">
        <signal name="clicked" handler="handle_button_clicked"/>
        <property name="label">Press me!</property>
        <property name="margin-top">12</property>
        <property name="margin-bottom">12</property>
        <property name="margin-start">12</property>
        <property name="margin-end">12</property>  
      </object>
    </child>
  </template>
</interface>

然后，我们在定义 handle_button_clicked 时应用 template_callbacks 宏。我们可以通过查看要处理的信号的 connect_* 方法来确定函数签名。在我们的例子中就是 connect_clicked. 它需要一个 Fn(&Self) 类型的函数。 Self 指的是我们的按钮。这意味着 handle_button_clicked 有一个 &CustomButton 类型的参数。

文件名：listings/composite_templates/3/window/imp.rs

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, CompositeTemplate};

use crate::custom_button::CustomButton;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub button: TemplateChild<CustomButton>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
        klass.bind_template_callbacks();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

#[gtk::template_callbacks]
impl Window {
    #[template_callback]
    fn handle_button_clicked(button: &CustomButton) {
        // Set the label to "Hello World!" after the button has been clicked on
        button.set_label("Hello World!");
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

然后，我们必须使用 bind_template_callbacks 绑定模板回调。我们还需要删除 window/imp.rs 中的 button.connect_clicked 回调。

文件名：listings/composite_templates/3/window/imp.rs

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, CompositeTemplate};

use crate::custom_button::CustomButton;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub button: TemplateChild<CustomButton>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
        klass.bind_template_callbacks();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

#[gtk::template_callbacks]
impl Window {
    #[template_callback]
    fn handle_button_clicked(button: &CustomButton) {
        // Set the label to "Hello World!" after the button has been clicked on
        button.set_label("Hello World!");
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

我们还可以访问部件的状态。比方说，我们要操作存储在 imp::Window 中的一个 number.

文件名：listings/composite_templates/4/window/imp.rs

use std::cell::Cell;

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, CompositeTemplate};

use crate::custom_button::CustomButton;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub button: TemplateChild<CustomButton>,
    pub number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
        klass.bind_template_callbacks();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

#[gtk::template_callbacks]
impl Window {
    #[template_callback]
    fn handle_button_clicked(&self, button: &CustomButton) {
        let number_increased = self.number.get() + 1;
        self.number.set(number_increased);
        button.set_label(&number_increased.to_string())
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

为了访问 widget 的状态，我们必须在信号标记中添加 swapped="true".

文件名：listings/composite_templates/4/resources/window.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="MyGtkAppWindow" parent="GtkApplicationWindow">
    <property name="title">My GTK App</property>
    <child>
      <object class="MyGtkAppCustomButton" id="button">
        <signal name="clicked" handler="handle_button_clicked" swapped="true"/>
        <property name="label">Press me!</property>
        <property name="margin-top">12</property>
        <property name="margin-bottom">12</property>
        <property name="margin-start">12</property>
        <property name="margin-end">12</property>  
      </object>
    </child>
  </template>
</interface>

现在，我们可以将 &self 作为 handle_button_clicked 的第一个参数。这样，我们就可以访问窗口的状态，从而对 number 进行操作。

文件名：listings/composite_templates/4/window/imp.rs

use std::cell::Cell;

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, CompositeTemplate};

use crate::custom_button::CustomButton;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub button: TemplateChild<CustomButton>,
    pub number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
        klass.bind_template_callbacks();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

#[gtk::template_callbacks]
impl Window {
    #[template_callback]
    fn handle_button_clicked(&self, button: &CustomButton) {
        let number_increased = self.number.get() + 1;
        self.number.set(number_increased);
        button.set_label(&number_increased.to_string())
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

Registering Types

现在我们使用模板回调，就不再访问模板子模板了。让我们删除它。

文件名：listings/composite_templates/5/window/imp.rs

use std::cell::Cell;

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, CompositeTemplate};

use crate::custom_button::CustomButton;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    pub number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
        klass.bind_template_callbacks();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

#[gtk::template_callbacks]
impl Window {
    #[template_callback]
    fn handle_button_clicked(&self, button: &CustomButton) {
        let number_increased = self.number.get() + 1;
        self.number.set(number_increased);
        button.set_label(&number_increased.to_string())
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

但是，当我们现在运行它时，GTK 不再将 MyGtkAppCustomButton 视为有效的对象类型。这是怎么回事？

Gtk-CRITICAL **: Error building template class 'MyGtkAppWindow' for an instance of
                 type 'MyGtkAppWindow': Invalid object type 'MyGtkAppCustomButton'

原来，添加模板子模板不仅可以方便地引用模板中的部件，它还能确保部件类型已注册。幸运的是，我们自己也可以做到这一点。

文件名：listings/composite_templates/6/window/imp.rs

use std::cell::Cell;

use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, CompositeTemplate};

use crate::custom_button::CustomButton;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    pub number: Cell<i32>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        // Register `CustomButton`
        CustomButton::ensure_type();

        klass.bind_template();
        klass.bind_template_callbacks();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

#[gtk::template_callbacks]
impl Window {
    #[template_callback]
    fn handle_button_clicked(&self, button: &CustomButton) {
        let number_increased = self.number.get() + 1;
        self.number.set(number_increased);
        button.set_label(&number_increased.to_string())
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

我们调用 class_init 中的 ensure_type 方法，瞧：我们的应用程序又能运行了。

结论

借助自定义控件，我们可以：

将状态和部分状态作为属性保留下来，
添加信号并且
覆盖行为。

借助复合模板，我们可以：

简要地描述复杂的用户界面，
轻松访问模板内的控件，
并为信号指定处理函数。

这里涉及的应用程序接口非常广泛，因此尤其是在开始学习时，您需要查看相关文档。 UI 文件的基本语法在 Builder 中解释，而控件的特定语法则在 Widget 中解释。如果某个控件接受附加元素，通常会在该控件的文档中加以说明。

在下一章中，我们将了解复合模板如何帮助我们创建稍大的应用程序，如 To-Do 应用程序。

创建一个简单的待办事项应用

在我们学习了这么多概念之后，终于到了付诸实践的时候了。我们要制作一个待办事项应用程序！

目前，我们只需制作一个最小版本即可。一个输入新任务的输入框和一个显示任务的列表视图就足够了。类似这样：

To-Do App with a couple of tasks, some of them crossed-off

窗口

这个模型可以用下面的复合模板来描述。

文件：listings/todo/1/resources/window.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="TodoWindow" parent="GtkApplicationWindow">
    <property name="width-request">360</property>
    <property name="title" translatable="yes">To-Do</property>
    <child>
      <object class="GtkBox">
        <property name="orientation">vertical</property>
        <property name="margin-top">12</property>
        <property name="margin-bottom">12</property>
        <property name="margin-start">12</property>
        <property name="margin-end">12</property>
        <property name="spacing">6</property>
        <child>
          <object class="GtkEntry" id="entry">
            <property name="placeholder-text" translatable="yes">Enter a Task…</property>
            <property name="secondary-icon-name">list-add-symbolic</property>
          </object>
        </child>
        <child>
          <object class="GtkScrolledWindow">
            <property name="hscrollbar-policy">never</property>
            <property name="min-content-height">360</property>
            <property name="vexpand">true</property>
            <child>
              <object class="GtkListView" id="tasks_list">
                <property name="valign">start</property>
              </object>
            </child>
          </object>
        </child>
      </object>
    </child>
  </template>
</interface>

为了使用复合模板，我们创建了一个自定义控件。它的父类是 gtk::ApplicationWindow，因此我们继承自它。像往常一样，我们必须列出除了 GObject 和 GInitiallyUnowned 之外的所有祖先和接口。

mod imp;

use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, NoSelection, SignalListItemFactory};
use gtk::{prelude::*, ListItem};

use crate::task_object::TaskObject;
use crate::task_row::TaskRow;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with selection and pass it to the list view
        let selection_model = NoSelection::new(Some(self.tasks()));
        self.imp().tasks_list.set_model(Some(&selection_model));
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }
}

然后初始化 imp::Window 的复合模板。我们存储输入框(entry)、列表视图(list view)和列表模型(list model)的引用。这将在我们以后为窗口添加方法时派上用场。之后，我们将添加用于初始化复合模板的典型模板。我们只需确保 window.ui 中模板的 class 属性与 NAME 匹配即可。

文件名：listings/todo/1/window/imp.rs

use std::cell::RefCell;

use glib::subclass::InitializingObject;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, CompositeTemplate, Entry, ListView};

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/Todo1/window.ui")]
pub struct Window {
    #[template_child]
    pub entry: TemplateChild<Entry>,
    #[template_child]
    pub tasks_list: TemplateChild<ListView>,
    pub tasks: RefCell<Option<gio::ListStore>>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "TodoWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Setup
        let obj = self.obj();
        obj.setup_tasks();
        obj.setup_callbacks();
        obj.setup_factory();
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

main.rs 也没有什么新东西。

文件名：listings/todo/1/main.rs

mod task_object;
mod task_row;
mod window;

use gtk::prelude::*;
use gtk::{gio, glib, Application};
use window::Window;

fn main() -> glib::ExitCode {
    // Register and include resources
    gio::resources_register_include!("todo_1.gresource")
        .expect("Failed to register resources.");

    // Create a new application
    let app = Application::builder()
        .application_id("org.gtk_rs.Todo1")
        .build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a new custom window and present it
    let window = Window::new(app);
    window.present();
}

最后，我们指定资源。这里已经包含了 task_row.ui，我们将在本章稍后处理。

文件名：listings/todo/1/resources/resources.gresource.xml

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/org/gtk_rs/Todo1/">
    <file compressed="true" preprocess="xml-stripblanks">task_row.ui</file>
    <file compressed="true" preprocess="xml-stripblanks">window.ui</file>
  </gresource>
</gresources>

任务对象

目前还不错。主用户界面已经完成，但输入框还不能对输入做出反应。另外，输入内容会放在哪里呢？我们甚至还没有建立列表模型。让我们开始吧！

正如在列表部件一章中所讨论的，我们首先要创建一个自定义 GObject。该对象将存储任务的状态，其中包括：

一个布尔值用于描述任务是否完成
一个字符串存储任务名称

文件名：listings/todo/1/task_object/mod.rs

mod imp;

use glib::Object;
use gtk::glib;

glib::wrapper! {
    pub struct TaskObject(ObjectSubclass<imp::TaskObject>);
}

impl TaskObject {
    pub fn new(completed: bool, content: String) -> Self {
        Object::builder()
            .property("completed", completed)
            .property("content", content)
            .build()
    }
}

#[derive(Default)]
pub struct TaskData {
    pub completed: bool,
    pub content: String,
}

与列表一章不同的是，状态存储在一个结构体中，而不是 imp::TaskObject 的单个成员中。这对于在后续章节中保存状态非常方便。

文件名：listings/todo/1/task_object/mod.rs

mod imp;

use glib::Object;
use gtk::glib;

glib::wrapper! {
    pub struct TaskObject(ObjectSubclass<imp::TaskObject>);
}

impl TaskObject {
    pub fn new(completed: bool, content: String) -> Self {
        Object::builder()
            .property("completed", completed)
            .property("content", content)
            .build()
    }
}

#[derive(Default)]
pub struct TaskData {
    pub completed: bool,
    pub content: String,
}

我们将把 completed 和 content 作为属性公开。由于数据现在是在一个结构体中，而不是在单个成员变量中，因此我们必须添加更多注解。对于每个属性，我们都要额外指定名称、类型和要访问的 TaskData 成员变量。

文件名：listings/todo/1/task_object/imp.rs

use std::cell::RefCell;

use glib::Properties;
use gtk::glib;
use gtk::prelude::*;
use gtk::subclass::prelude::*;

use super::TaskData;

// Object holding the state
#[derive(Properties, Default)]
#[properties(wrapper_type = super::TaskObject)]
pub struct TaskObject {
    #[property(name = "completed", get, set, type = bool, member = completed)]
    #[property(name = "content", get, set, type = String, member = content)]
    pub data: RefCell<TaskData>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for TaskObject {
    const NAME: &'static str = "TodoTaskObject";
    type Type = super::TaskObject;
}

// Trait shared by all GObjects
#[glib::derived_properties]
impl ObjectImpl for TaskObject {}

任务行

下面我们来看看各个任务。任务的行应该是这样的：

同样，我们用一个复合模板来描述模型。

文件名：listings/todo/1/resources/task_row.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="TodoTaskRow" parent="GtkBox">
    <child>
      <object class="GtkCheckButton" id="completed_button">
        <property name="margin-top">12</property>
        <property name="margin-bottom">12</property>
        <property name="margin-start">12</property>
        <property name="margin-end">12</property>
      </object>
    </child>
    <child>
      <object class="GtkLabel" id="content_label">
        <property name="margin-top">12</property>
        <property name="margin-bottom">12</property>
        <property name="margin-start">12</property>
        <property name="margin-end">12</property>
      </object>
    </child>
  </template>
</interface>

在这个代码中，我们用 gtk:Box 实现 TaskRow：

文件名：listings/todo/1/task_row/mod.rs

mod imp;

use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, pango};
use pango::{AttrInt, AttrList};

use crate::task_object::TaskObject;

glib::wrapper! {
    pub struct TaskRow(ObjectSubclass<imp::TaskRow>)
    @extends gtk::Box, gtk::Widget,
    @implements gtk::Accessible, gtk::Buildable, gtk::ConstraintTarget, gtk::Orientable;
}

impl Default for TaskRow {
    fn default() -> Self {
        Self::new()
    }
}

impl TaskRow {
    pub fn new() -> Self {
        Object::builder().build()
    }

    pub fn bind(&self, task_object: &TaskObject) {
        // Get state
        let completed_button = self.imp().completed_button.get();
        let content_label = self.imp().content_label.get();
        let mut bindings = self.imp().bindings.borrow_mut();

        // Bind `task_object.completed` to `task_row.completed_button.active`
        let completed_button_binding = task_object
            .bind_property("completed", &completed_button, "active")
            .bidirectional()
            .sync_create()
            .build();
        // Save binding
        bindings.push(completed_button_binding);

        // Bind `task_object.content` to `task_row.content_label.label`
        let content_label_binding = task_object
            .bind_property("content", &content_label, "label")
            .sync_create()
            .build();
        // Save binding
        bindings.push(content_label_binding);

        // Bind `task_object.completed` to `task_row.content_label.attributes`
        let content_label_binding = task_object
            .bind_property("completed", &content_label, "attributes")
            .sync_create()
            .transform_to(|_, active| {
                let attribute_list = AttrList::new();
                if active {
                    // If "active" is true, content of the label will be strikethrough
                    let attribute = AttrInt::new_strikethrough(true);
                    attribute_list.insert(attribute);
                }
                Some(attribute_list.to_value())
            })
            .build();
        // Save binding
        bindings.push(content_label_binding);
    }

    pub fn unbind(&self) {
        // Unbind all stored bindings
        for binding in self.imp().bindings.borrow_mut().drain(..) {
            binding.unbind();
        }
    }
}

在 imp::TaskRow 中，我们保存了 completed_button 和 content_label 的引用。我们还存储了绑定的可变vector。当我们把 TaskObject 的状态绑定到相应的 TaskRow 时，就会明白为什么需要这样做了。

文件名：listings/todo/1/task_row/imp.rs

use std::cell::RefCell;

use glib::Binding;
use gtk::subclass::prelude::*;
use gtk::{glib, CheckButton, CompositeTemplate, Label};

// Object holding the state
#[derive(Default, CompositeTemplate)]
#[template(resource = "/org/gtk_rs/Todo1/task_row.ui")]
pub struct TaskRow {
    #[template_child]
    pub completed_button: TemplateChild<CheckButton>,
    #[template_child]
    pub content_label: TemplateChild<Label>,
    // Vector holding the bindings to properties of `TaskObject`
    pub bindings: RefCell<Vec<Binding>>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for TaskRow {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "TodoTaskRow";
    type Type = super::TaskRow;
    type ParentType = gtk::Box;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &glib::subclass::InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for TaskRow {}

// Trait shared by all widgets
impl WidgetImpl for TaskRow {}

// Trait shared by all boxes
impl BoxImpl for TaskRow {}

现在我们可以将所有内容整合在一起。我们重写 imp::Window::constructed，以便在创建窗口时设置窗口内容。

文件名：listings/todo/1/window/imp.rs

use std::cell::RefCell;

use glib::subclass::InitializingObject;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, CompositeTemplate, Entry, ListView};

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/Todo1/window.ui")]
pub struct Window {
    #[template_child]
    pub entry: TemplateChild<Entry>,
    #[template_child]
    pub tasks_list: TemplateChild<ListView>,
    pub tasks: RefCell<Option<gio::ListStore>>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "TodoWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Setup
        let obj = self.obj();
        obj.setup_tasks();
        obj.setup_callbacks();
        obj.setup_factory();
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

由于我们需要经常访问列表模型，为此我们添加了便捷方法 Window::tasks. 在 Window::setup_tasks 中，我们创建了一个新模型。然后在 imp::Window 和 gtk::ListView 中存储对模型的引用。

mod imp;

use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, NoSelection, SignalListItemFactory};
use gtk::{prelude::*, ListItem};

use crate::task_object::TaskObject;
use crate::task_row::TaskRow;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with selection and pass it to the list view
        let selection_model = NoSelection::new(Some(self.tasks()));
        self.imp().tasks_list.set_model(Some(&selection_model));
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }
}

我们还创建了一个方法 new_task，它可以获取条目的内容、清除条目并使用内容创建新任务。

mod imp;

use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, NoSelection, SignalListItemFactory};
use gtk::{prelude::*, ListItem};

use crate::task_object::TaskObject;
use crate::task_row::TaskRow;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with selection and pass it to the list view
        let selection_model = NoSelection::new(Some(self.tasks()));
        self.imp().tasks_list.set_model(Some(&selection_model));
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }
}

在 Window::setup_callbacks 中，我们连接到输入框的 "activate"（激活）信号。当我们在输入框中按下回车键时，就会触发该信号。然后会创建一个包含内容的新 TaskObject，并将其附加到模型中。最后，输入框将被清空。

mod imp;

use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, NoSelection, SignalListItemFactory};
use gtk::{prelude::*, ListItem};

use crate::task_object::TaskObject;
use crate::task_row::TaskRow;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with selection and pass it to the list view
        let selection_model = NoSelection::new(Some(self.tasks()));
        self.imp().tasks_list.set_model(Some(&selection_model));
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }
}

gtk::ListView 的列表元素是由一个工厂生产的。在继续实现之前，让我们退一步思考一下我们期望的行为。我们还希望 TaskRow 的 completed_button 跟随 TaskObject 的 completed。这可以通过类似于列表一章中的表达式来实现。

但是，如果我们切换 TaskRow 的 completed_button 的状态，TaskObject 的 completed 也应随之改变。遗憾的是，表达式无法处理双向关系。这意味着我们必须使用属性绑定。当不再需要时，我们需要手动解除绑定。

我们将在 Window::setup_factory 的"设置(setup)"步骤中创建空的 TaskRow 对象，并在"绑定(bind)"和"解除绑定(unbind)"步骤中处理绑定问题。

mod imp;

use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, NoSelection, SignalListItemFactory};
use gtk::{prelude::*, ListItem};

use crate::task_object::TaskObject;
use crate::task_row::TaskRow;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with selection and pass it to the list view
        let selection_model = NoSelection::new(Some(self.tasks()));
        self.imp().tasks_list.set_model(Some(&selection_model));
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }
}

在 TaskRow::bind 中绑定属性的工作原理与前几章相同。唯一不同的是，我们将绑定存储在一个vector(vector)中。这一点很有必要，因为当您滚动列表时，任务行( TaskRow )会被重复使用。这意味着随着时间的推移，任务行需要绑定到一个新的任务对象，并且必须从旧的任务对象中解除绑定。只有在能访问存储的 glib::Binding 时，解除绑定才会起作用。

文件名：listings/todo/1/task_row/mod.rs

mod imp;

use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, pango};
use pango::{AttrInt, AttrList};

use crate::task_object::TaskObject;

glib::wrapper! {
    pub struct TaskRow(ObjectSubclass<imp::TaskRow>)
    @extends gtk::Box, gtk::Widget,
    @implements gtk::Accessible, gtk::Buildable, gtk::ConstraintTarget, gtk::Orientable;
}

impl Default for TaskRow {
    fn default() -> Self {
        Self::new()
    }
}

impl TaskRow {
    pub fn new() -> Self {
        Object::builder().build()
    }

    pub fn bind(&self, task_object: &TaskObject) {
        // Get state
        let completed_button = self.imp().completed_button.get();
        let content_label = self.imp().content_label.get();
        let mut bindings = self.imp().bindings.borrow_mut();

        // Bind `task_object.completed` to `task_row.completed_button.active`
        let completed_button_binding = task_object
            .bind_property("completed", &completed_button, "active")
            .bidirectional()
            .sync_create()
            .build();
        // Save binding
        bindings.push(completed_button_binding);

        // Bind `task_object.content` to `task_row.content_label.label`
        let content_label_binding = task_object
            .bind_property("content", &content_label, "label")
            .sync_create()
            .build();
        // Save binding
        bindings.push(content_label_binding);

        // Bind `task_object.completed` to `task_row.content_label.attributes`
        let content_label_binding = task_object
            .bind_property("completed", &content_label, "attributes")
            .sync_create()
            .transform_to(|_, active| {
                let attribute_list = AttrList::new();
                if active {
                    // If "active" is true, content of the label will be strikethrough
                    let attribute = AttrInt::new_strikethrough(true);
                    attribute_list.insert(attribute);
                }
                Some(attribute_list.to_value())
            })
            .build();
        // Save binding
        bindings.push(content_label_binding);
    }

    pub fn unbind(&self) {
        // Unbind all stored bindings
        for binding in self.imp().bindings.borrow_mut().drain(..) {
            binding.unbind();
        }
    }
}

TaskRow::unbind 负责清理工作。它会遍历 vector 并解除每个绑定。最后，它会清除该 vector.

文件名：listings/todo/1/task_row/mod.rs

mod imp;

use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{glib, pango};
use pango::{AttrInt, AttrList};

use crate::task_object::TaskObject;

glib::wrapper! {
    pub struct TaskRow(ObjectSubclass<imp::TaskRow>)
    @extends gtk::Box, gtk::Widget,
    @implements gtk::Accessible, gtk::Buildable, gtk::ConstraintTarget, gtk::Orientable;
}

impl Default for TaskRow {
    fn default() -> Self {
        Self::new()
    }
}

impl TaskRow {
    pub fn new() -> Self {
        Object::builder().build()
    }

    pub fn bind(&self, task_object: &TaskObject) {
        // Get state
        let completed_button = self.imp().completed_button.get();
        let content_label = self.imp().content_label.get();
        let mut bindings = self.imp().bindings.borrow_mut();

        // Bind `task_object.completed` to `task_row.completed_button.active`
        let completed_button_binding = task_object
            .bind_property("completed", &completed_button, "active")
            .bidirectional()
            .sync_create()
            .build();
        // Save binding
        bindings.push(completed_button_binding);

        // Bind `task_object.content` to `task_row.content_label.label`
        let content_label_binding = task_object
            .bind_property("content", &content_label, "label")
            .sync_create()
            .build();
        // Save binding
        bindings.push(content_label_binding);

        // Bind `task_object.completed` to `task_row.content_label.attributes`
        let content_label_binding = task_object
            .bind_property("completed", &content_label, "attributes")
            .sync_create()
            .transform_to(|_, active| {
                let attribute_list = AttrList::new();
                if active {
                    // If "active" is true, content of the label will be strikethrough
                    let attribute = AttrInt::new_strikethrough(true);
                    attribute_list.insert(attribute);
                }
                Some(attribute_list.to_value())
            })
            .build();
        // Save binding
        bindings.push(content_label_binding);
    }

    pub fn unbind(&self) {
        // Unbind all stored bindings
        for binding in self.imp().bindings.borrow_mut().drain(..) {
            binding.unbind();
        }
    }
}

就这样，我们创建了一个基本的待办事项应用程序！在接下来的章节中，我们将添加其他功能以对其进行扩展。

动作(Actions)

到目前为止，我们已经学会了许多将控件粘在一起的方法。我们可以通过通道发送消息、发射信号、共享引用计数状态和绑定属性。现在，我们将通过学习动作(Actions)来完成我们的设置。

动作是绑定到某个 GObject 的功能。让我们来看看最简单的情况，即在没有参数的情况下激活一个动作。

文件名：listings/actions/1/main.rs

use gio::ActionEntry;
use gtk::prelude::*;
use gtk::{gio, glib, Application, ApplicationWindow};

const APP_ID: &str = "org.gtk_rs.Actions1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Set keyboard accelerator to trigger "win.close".
    app.set_accels_for_action("win.close", &["<Ctrl>W"]);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a window and set the title
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .width_request(360)
        .build();

    // Add action "close" to `window` taking no parameter
    let action_close = ActionEntry::builder("close")
        .activate(|window: &ApplicationWindow, _, _| {
            window.close();
        })
        .build();
    window.add_action_entries([action_close]);

    // Present window
    window.present();
}

首先，我们创建了一个名为 "close" 的新 gio::ActionEntry ，它不需要任何参数。我们还连接了一个回调，用于在激活动作时关闭窗口。最后，我们通过 add_action_entries将操作条目添加到窗口中。

文件名：listings/actions/1/main.rs

use gio::ActionEntry;
use gtk::prelude::*;
use gtk::{gio, glib, Application, ApplicationWindow};

const APP_ID: &str = "org.gtk_rs.Actions1";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Set keyboard accelerator to trigger "win.close".
    app.set_accels_for_action("win.close", &["<Ctrl>W"]);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a window and set the title
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .width_request(360)
        .build();

    // Add action "close" to `window` taking no parameter
    let action_close = ActionEntry::builder("close")
        .activate(|window: &ApplicationWindow, _, _| {
            window.close();
        })
        .build();
    window.add_action_entries([action_close]);

    // Present window
    window.present();
}

使用动作的最常见原因之一是快捷键，因此我们在此添加了一个。通过 set_accels_for_action，可以为某个动作分配一个或多个快捷键。有关 accelerator_parse的语法，请查阅文档。

在我们继续讨论动作的其他方面之前，让我们先来了解一下这里的一些奇特之处。 "win.close" 中的 "win" 是动作组。但 GTK 如何知道 "win" 是我们窗口的动作组呢？答案是，在窗口和应用程序中添加操作非常普遍，因此已经有两个预定义的组可用：

"app" 用于应用程序的全局动作，
"win" 用于与应用程序窗口相关的动作。

我们可以通过 insert_action_group 方法为任何控件添加动作组。让我们将动作添加到动作组 "custom-group"，然后将该组添加到我们的窗口。该动作项(action entry)不再是针对我们的窗口，"activate（激活）" 回调的第一个参数类型是 SimpleActionGroup，而不是 ApplicationWindow。这意味着我们必须将窗口克隆到闭包中。

文件名：listings/actions/2/main.rs

use gio::ActionEntry;
use glib::clone;
use gtk::gio::SimpleActionGroup;
use gtk::prelude::*;
use gtk::{gio, glib, Application, ApplicationWindow};

const APP_ID: &str = "org.gtk_rs.Actions2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);
    // Set keyboard accelerator to trigger "custom-group.close".
    app.set_accels_for_action("custom-group.close", &["<Ctrl>W"]);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a window and set the title
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .width_request(360)
        .build();

    // Add action "close" to `window` taking no parameter
    let action_close = ActionEntry::builder("close")
        .activate(clone!(
            #[weak]
            window,
            move |_, _, _| {
                window.close();
            }
        ))
        .build();

    // Create a new action group and add actions to it
    let actions = SimpleActionGroup::new();
    actions.add_action_entries([action_close]);
    window.insert_action_group("custom-group", Some(&actions));

    // Present window
    window.present();
}

如果我们将快捷键绑定到 "custom-group.close"，它就会像以前一样工作。

文件名：listings/actions/2/main.rs

use gio::ActionEntry;
use glib::clone;
use gtk::gio::SimpleActionGroup;
use gtk::prelude::*;
use gtk::{gio, glib, Application, ApplicationWindow};

const APP_ID: &str = "org.gtk_rs.Actions2";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);
    // Set keyboard accelerator to trigger "custom-group.close".
    app.set_accels_for_action("custom-group.close", &["<Ctrl>W"]);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    // Create a window and set the title
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .width_request(360)
        .build();

    // Add action "close" to `window` taking no parameter
    let action_close = ActionEntry::builder("close")
        .activate(clone!(
            #[weak]
            window,
            move |_, _, _| {
                window.close();
            }
        ))
        .build();

    // Create a new action group and add actions to it
    let actions = SimpleActionGroup::new();
    actions.add_action_entries([action_close]);
    window.insert_action_group("custom-group", Some(&actions));

    // Present window
    window.present();
}

此外，如果我们有多个相同窗口的实例，我们会希望在激活 "win.close" 时只关闭当前聚焦的窗口。事实上，"win.close" 将被派发到当前聚焦的窗口。不过，这也意味着我们实际上为每个窗口实例定义了一个动作。如果我们想使用一个全局动作，可以在应用程序上调用 add_action_entries.

添加 "win.close" 作为一个简单的示例非常有用。不过，今后我们将使用预定义的 "window.close" 操作，其作用完全相同。

参数和状态

与大多数函数一样，动作可以接受一个参数。不过，与大多数函数不同的是，它也可以是有状态的。让我们看看它是如何工作的。

文件名：listings/actions/3/main.rs

use gio::ActionEntry;
use gtk::prelude::*;
use gtk::{
    gio, glib, Align, Application, ApplicationWindow, Button, Label, Orientation,
};

const APP_ID: &str = "org.gtk_rs.Actions3";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    let original_state = 0;
    let label = Label::builder()
        .label(format!("Counter: {original_state}"))
        .build();

    // Create a button with label
    let button = Button::builder().label("Press me!").build();

    // Connect to "clicked" signal of `button`
    button.connect_clicked(move |button| {
        // Activate "win.count" and pass "1" as parameter
        let parameter = 1;
        button
            .activate_action("win.count", Some(&parameter.to_variant()))
            .expect("The action does not exist.");
    });

    // Create a `gtk::Box` and add `button` and `label` to it
    let gtk_box = gtk::Box::builder()
        .orientation(Orientation::Vertical)
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .spacing(12)
        .halign(Align::Center)
        .build();
    gtk_box.append(&button);
    gtk_box.append(&label);

    // Create a window, set the title and add `gtk_box` to it
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .width_request(360)
        .child(&gtk_box)
        .build();

    // Add action "count" to `window` taking an integer as parameter
    let action_count = ActionEntry::builder("count")
        .parameter_type(Some(&i32::static_variant_type()))
        .state(original_state.to_variant())
        .activate(move |_, action, parameter| {
            // Get state
            let mut state = action
                .state()
                .expect("Could not get state.")
                .get::<i32>()
                .expect("The variant needs to be of type `i32`.");

            // Get parameter
            let parameter = parameter
                .expect("Could not get parameter.")
                .get::<i32>()
                .expect("The variant needs to be of type `i32`.");

            // Increase state by parameter and store state
            state += parameter;
            action.set_state(&state.to_variant());

            // Update label with new state
            label.set_label(&format!("Counter: {state}"));
        })
        .build();
    window.add_action_entries([action_count]);

    // Present window
    window.present();
}

在这里，我们创建了一个 "win.count" 动作，每次激活时都会按给定参数增加状态。它还负责用当前状态更新标签。每次点击按钮都会激活动作，同时将 "1" 作为参数传递。我们的应用程序就是这样运行的：

可执行动作的(Actionable)

将动作连接到按钮的 "clicked"（点击）信号是一个典型的使用案例，这就是为什么所有按钮都实现了 Actionable 接口。这样，就可以通过设置 "action-name" 属性来指定动作。如果动作接受参数，则可通过 "action-target" 属性进行设置。有了 ButtonBuilder, 我们可以通过调用其方法来设置一切。

文件名：listings/actions/4/main.rs

use gio::ActionEntry;
use gtk::prelude::*;
use gtk::{
    gio, glib, Align, Application, ApplicationWindow, Button, Label, Orientation,
};

const APP_ID: &str = "org.gtk_rs.Actions4";

fn main() -> glib::ExitCode {
    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to "activate" signal of `app`
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn build_ui(app: &Application) {
    let original_state = 0;
    let label = Label::builder()
        .label(format!("Counter: {original_state}"))
        .build();
    // Create a button with label and action
    let button = Button::builder()
        .label("Press me!")
        .action_name("win.count")
        .action_target(&1.to_variant())
        .build();

    // Create `gtk_box` and add `button` and `label` to it
    let gtk_box = gtk::Box::builder()
        .orientation(Orientation::Vertical)
        .margin_top(12)
        .margin_bottom(12)
        .margin_start(12)
        .margin_end(12)
        .spacing(12)
        .halign(Align::Center)
        .build();
    gtk_box.append(&button);
    gtk_box.append(&label);

    // Create a window and set the title
    let window = ApplicationWindow::builder()
        .application(app)
        .title("My GTK App")
        .width_request(360)
        .child(&gtk_box)
        .build();

    // Add action "count" to `window` taking an integer as parameter
    let action_count = ActionEntry::builder("count")
        .parameter_type(Some(&i32::static_variant_type()))
        .state(original_state.to_variant())
        .activate(move |_, action, parameter| {
            // Get state
            let mut state = action
                .state()
                .expect("Could not get state.")
                .get::<i32>()
                .expect("The variant needs to be of type `i32`.");

            // Get parameter
            let parameter = parameter
                .expect("Could not get parameter.")
                .get::<i32>()
                .expect("The variant needs to be of type `i32`.");

            // Increase state by parameter and store state
            state += parameter;
            action.set_state(&state.to_variant());

            // Update label with new state
            label.set_label(&format!("Counter: {state}"));
        })
        .build();
    window.add_action_entries([action_count]);

    // Present window
    window.present();
}

还可以通过界面生成器轻松访问可执行动作的部件。像往常一样，我们通过一个复合模板来创建窗口。然后，我们可以在模板中设置 "动作名称(action-name)"和 "动作目标(action-target)"属性。

文件名：listings/actions/5/resources/window.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="MyGtkAppWindow" parent="GtkApplicationWindow">
    <property name="title">My GTK App</property>
    <child>
      <object class="GtkBox" id="gtk_box">
        <property name="orientation">vertical</property>
        <property name="margin-top">12</property>
        <property name="margin-bottom">12</property>
        <property name="margin-start">12</property>
        <property name="margin-end">12</property>
        <property name="spacing">12</property>
        <property name="halign">center</property>
        <child>
          <object class="GtkButton" id="button">
            <property name="label">Press me!</property>
            <property name="action-name">win.count</property>
            <property name="action-target">1</property>
          </object>
        </child>
        <child>
          <object class="GtkLabel" id="label">
            <property name="label">Counter: 0</property>
          </object>
        </child>
      </object>
    </child>
  </template>
</interface>

我们将在 Window::setup_actions 方法中连接操作并将其添加到窗口。

文件名：listings/actions/5/window/mod.rs

mod imp;

use gio::ActionEntry;
use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application};

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_actions(&self) {
        // Add stateful action "count" to `window` taking an integer as parameter
        let original_state = 0;
        let action_count = ActionEntry::builder("count")
            .parameter_type(Some(&i32::static_variant_type()))
            .state(original_state.to_variant())
            .activate(move |window: &Self, action, parameter| {
                // Get state
                let mut state = action
                    .state()
                    .expect("Could not get state.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Get parameter
                let parameter = parameter
                    .expect("Could not get parameter.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Increase state by parameter and store state
                state += parameter;
                action.set_state(&state.to_variant());

                // Update label with new state
                window.imp().label.set_label(&format!("Counter: {state}"));
            })
            .build();
        self.add_action_entries([action_count]);
    }
}

最后，setup_actions 将在 constructed 函数内调用。

文件名：listings/actions/5/window/imp.rs

use glib::subclass::InitializingObject;
use gtk::subclass::prelude::*;
use gtk::{glib, CompositeTemplate, Label};

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub label: TemplateChild<Label>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Add actions
        self.obj().setup_actions();
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

该应用程序的行为与我们之前的示例相同，但它将使我们在下一部分添加菜单时更加简单。

菜单

如果要创建菜单，就必须使用动作，而且要使用界面生成器。通常情况下，菜单条目中的操作符合以下三种描述之一：

无参数和无状态，
或无参数和布尔状态，
或字符串参数和字符串状态。

让我们修改我们的小程序来演示这些情况。首先，我们扩展 setup_actions。对于不带参数或状态的动作，我们可以使用预定义的 "window.close" 动作。因此，我们无需在此处添加任何内容。

通过动作 "button-frame"，我们可以操作按钮的 "has-frame" 属性。这里的惯例是，不带参数并且为布尔状态的操作应该像切换操作一样。这意味着调用者可以期待布尔状态在激活动作后切换。幸运的是，这正是带有布尔属性的 gio::PropertyAction 的默认行为。

文件名：listings/actions/6/window/mod.rs

mod imp;

use gio::{ActionEntry, PropertyAction};
use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, Orientation};

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_actions(&self) {
        // Add stateful action "count" to `window` taking an integer as parameter
        let original_state = 0;
        let action_count = ActionEntry::builder("count")
            .parameter_type(Some(&i32::static_variant_type()))
            .state(original_state.to_variant())
            .activate(move |window: &Self, action, parameter| {
                // Get state
                let mut state = action
                    .state()
                    .expect("Could not get state.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Get parameter
                let parameter = parameter
                    .expect("Could not get parameter.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Increase state by parameter and store state
                state += parameter;
                action.set_state(&state.to_variant());

                // Update label with new state
                window.imp().label.set_label(&format!("Counter: {state}"));
            })
            .build();
        // Add property action "button-frame" to `window`
        let button = self.imp().button.get();
        let action_button_frame =
            PropertyAction::new("button-frame", &button, "has-frame");
        self.add_action(&action_button_frame);

        // Add stateful action "orientation" to `window` taking a string as parameter
        let action_orientation = ActionEntry::builder("orientation")
            .parameter_type(Some(&String::static_variant_type()))
            .state("Vertical".to_variant())
            .activate(move |window: &Self, action, parameter| {
                // Get parameter
                let parameter = parameter
                    .expect("Could not get parameter.")
                    .get::<String>()
                    .expect("The value needs to be of type `String`.");

                let orientation = match parameter.as_str() {
                    "Horizontal" => Orientation::Horizontal,
                    "Vertical" => Orientation::Vertical,
                    _ => unreachable!(),
                };

                // Set orientation and save state
                window.imp().gtk_box.set_orientation(orientation);
                action.set_state(&parameter.to_variant());
            })
            .build();
        self.add_action_entries([action_count, action_orientation]);
    }
}

当您需要一个操作 GObject 属性的动作时，PropertyAction 就会派上用场。属性将作为动作的状态。如上所述，如果属性是布尔型，则动作没有参数，并在激活时切换属性。在所有其他情况下，操作都有一个与属性类型相同的参数。激活动作时，属性会被设置为与动作参数相同的值。

最后，我们添加了 "win.orientation"，一个带有字符串参数和字符串状态的动作。该操作可用于改变 gtk_box 的朝向。这里的惯例是状态(state)应设置为给定的参数。我们并不需要动作状态来实现方向切换，但它在使菜单显示当前朝向时非常有用。

文件名：listings/actions/6/window/mod.rs

mod imp;

use gio::{ActionEntry, PropertyAction};
use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, Orientation};

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_actions(&self) {
        // Add stateful action "count" to `window` taking an integer as parameter
        let original_state = 0;
        let action_count = ActionEntry::builder("count")
            .parameter_type(Some(&i32::static_variant_type()))
            .state(original_state.to_variant())
            .activate(move |window: &Self, action, parameter| {
                // Get state
                let mut state = action
                    .state()
                    .expect("Could not get state.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Get parameter
                let parameter = parameter
                    .expect("Could not get parameter.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Increase state by parameter and store state
                state += parameter;
                action.set_state(&state.to_variant());

                // Update label with new state
                window.imp().label.set_label(&format!("Counter: {state}"));
            })
            .build();
        // Add property action "button-frame" to `window`
        let button = self.imp().button.get();
        let action_button_frame =
            PropertyAction::new("button-frame", &button, "has-frame");
        self.add_action(&action_button_frame);

        // Add stateful action "orientation" to `window` taking a string as parameter
        let action_orientation = ActionEntry::builder("orientation")
            .parameter_type(Some(&String::static_variant_type()))
            .state("Vertical".to_variant())
            .activate(move |window: &Self, action, parameter| {
                // Get parameter
                let parameter = parameter
                    .expect("Could not get parameter.")
                    .get::<String>()
                    .expect("The value needs to be of type `String`.");

                let orientation = match parameter.as_str() {
                    "Horizontal" => Orientation::Horizontal,
                    "Vertical" => Orientation::Vertical,
                    _ => unreachable!(),
                };

                // Set orientation and save state
                window.imp().gtk_box.set_orientation(orientation);
                action.set_state(&parameter.to_variant());
            })
            .build();
        self.add_action_entries([action_count, action_orientation]);
    }
}

尽管 gio::Menu 也可以通过绑定创建，但最方便的方法还是使用界面生成器。我们可以在模板前添加菜单。

文件名：listings/actions/6/resources/window.ui

 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <menu id="main-menu">
+    <item>
+      <attribute name="label" translatable="yes">_Close window</attribute>
+      <attribute name="action">window.close</attribute>
+    </item>
+    <item>
+      <attribute name="label" translatable="yes">_Toggle button frame</attribute>
+      <attribute name="action">win.button-frame</attribute>
+    </item>
+    <section>
+      <attribute name="label" translatable="yes">Orientation</attribute>
+      <item>
+        <attribute name="label" translatable="yes">_Horizontal</attribute>
+        <attribute name="action">win.orientation</attribute>
+        <attribute name="target">Horizontal</attribute>
+      </item>
+      <item>
+        <attribute name="label" translatable="yes">_Vertical</attribute>
+        <attribute name="action">win.orientation</attribute>
+        <attribute name="target">Vertical</attribute>
+      </item>
+    </section>
+  </menu>
   <template class="MyGtkAppWindow" parent="GtkApplicationWindow">
     <property name="title">My GTK App</property>
+    <property name="width-request">360</property>
+    <child type="titlebar">
+      <object class="GtkHeaderBar">
+        <child type ="end">
+          <object class="GtkMenuButton">
+            <property name="icon-name">open-menu-symbolic</property>
+            <property name="menu-model">main-menu</property>
+          </object>
+        </child>
+      </object>
+    </child>
     <child>
       <object class="GtkBox" id="gtk_box">
         <property name="orientation">vertical</property>

由于我们通过 menu-model 属性将菜单连接到了 gtk::MenuButton ，因此菜单(Menu)应为 gtk::PopoverMenu. PopoverMenu 的文档还为界面生成器解释了其 xml 语法。

还要注意我们是如何指定目标的：

<attribute name="target">Horizontal</attribute>

字符串是目标的默认类型，因此我们无需指定类型。对于其他类型的目标，则需要手动指定正确的 GVariant 格式字符串。例如，一个值为 "5 "的 i32 变量对应的格式如下：

<attribute name="target" type="i">5</attribute>

这就是该应用程序的实际效果：

我们将菜单按钮(MenuButton)的属性 "icon-name" 设置为 "open-menu-symbolic"，从而更改了菜单按钮的图标。您可以在图标库中找到更多图标。这些图标可以嵌入 gio::Resource ，然后在合成模板（或其他地方）中引用。

设置(Settings)

菜单项很好地显示了有状态动作的状态，但在应用程序关闭后，对该状态的所有更改都会丢失。像往常一样，我们使用 gio::Settings 解决这个问题。首先，我们创建一个 schema，其中包含与之前创建的有状态操作相对应的设置。

文件名：listings/actions/7/org.gtk_rs.Actions7.gschema.xml

<?xml version="1.0" encoding="utf-8"?>
<schemalist>
  <schema id="org.gtk_rs.Actions7" path="/org/gtk_rs/Actions7/">
    <key name="button-frame" type="b">
      <default>true</default>
      <summary>Whether the button has a frame</summary>
    </key>
    <key name="orientation" type="s">
      <choices>
        <choice value='Horizontal'/>
        <choice value='Vertical'/>
      </choices>
      <default>'Vertical'</default>
      <summary>Orientation of GtkBox</summary>
    </key>
  </schema>
</schemalist>

同样，我们按照设置一章中描述来安装 schema. 然后将设置添加到 imp::Window. 由于 gio::Settings 没有实现 Default，我们将其封装在 std::cell::OnceCell 中。

文件名：listings/actions/7/window/imp.rs

use gio::Settings;
use glib::subclass::InitializingObject;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Button, CompositeTemplate, Label};
use std::cell::OnceCell;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub gtk_box: TemplateChild<gtk::Box>,
    #[template_child]
    pub button: TemplateChild<Button>,
    #[template_child]
    pub label: TemplateChild<Label>,
    pub settings: OnceCell<Settings>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Setup
        let obj = self.obj();
        obj.setup_settings();
        obj.setup_actions();
        obj.bind_settings();
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

现在，我们创建一些函数，使设置更容易访问。

文件名：listings/actions/7/window/mod.rs

mod imp;

use gio::{ActionEntry, Settings};
use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, Orientation};

use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn setup_actions(&self) {
        // Add stateful action "count" to `window` taking an integer as parameter
        let original_state = 0;
        let action_count = ActionEntry::builder("count")
            .parameter_type(Some(&i32::static_variant_type()))
            .state(original_state.to_variant())
            .activate(move |window: &Self, action, parameter| {
                // Get state
                let mut state = action
                    .state()
                    .expect("Could not get state.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Get parameter
                let parameter = parameter
                    .expect("Could not get parameter.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Increase state by parameter and store state
                state += parameter;
                action.set_state(&state.to_variant());

                // Update label with new state
                window.imp().label.set_label(&format!("Counter: {state}"));
            })
            .build();
        self.add_action_entries([action_count]);

        // Create action from key "button-frame" and add to action group "win"
        let action_button_frame = self.settings().create_action("button-frame");
        self.add_action(&action_button_frame);

        // Create action from key "orientation" and add to action group "win"
        let action_orientation = self.settings().create_action("orientation");
        self.add_action(&action_orientation);
    }

    fn bind_settings(&self) {
        // Bind setting "button-frame" to "has-frame" property of `button`
        let button = self.imp().button.get();
        self.settings()
            .bind("button-frame", &button, "has-frame")
            .build();

        // Bind setting "orientation" to "orientation" property of `button`
        let gtk_box = self.imp().gtk_box.get();
        self.settings()
            .bind("orientation", &gtk_box, "orientation")
            .mapping(|variant, _| {
                let orientation = variant
                    .get::<String>()
                    .expect("The variant needs to be of type `String`.");

                let orientation = match orientation.as_str() {
                    "Horizontal" => Orientation::Horizontal,
                    "Vertical" => Orientation::Vertical,
                    _ => unreachable!(),
                };

                Some(orientation.to_value())
            })
            .build();
    }
}

通过设置条目创建有状态的动作非常常见，因此设置(Settings)提供了一种方法来实现这一目的。我们使用 create_action 方法创建动作，然后将其添加到窗口的动作组中。

文件名：listings/actions/7/window/mod.rs

mod imp;

use gio::{ActionEntry, Settings};
use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, Orientation};

use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn setup_actions(&self) {
        // Add stateful action "count" to `window` taking an integer as parameter
        let original_state = 0;
        let action_count = ActionEntry::builder("count")
            .parameter_type(Some(&i32::static_variant_type()))
            .state(original_state.to_variant())
            .activate(move |window: &Self, action, parameter| {
                // Get state
                let mut state = action
                    .state()
                    .expect("Could not get state.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Get parameter
                let parameter = parameter
                    .expect("Could not get parameter.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Increase state by parameter and store state
                state += parameter;
                action.set_state(&state.to_variant());

                // Update label with new state
                window.imp().label.set_label(&format!("Counter: {state}"));
            })
            .build();
        self.add_action_entries([action_count]);

        // Create action from key "button-frame" and add to action group "win"
        let action_button_frame = self.settings().create_action("button-frame");
        self.add_action(&action_button_frame);

        // Create action from key "orientation" and add to action group "win"
        let action_orientation = self.settings().create_action("orientation");
        self.add_action(&action_orientation);
    }

    fn bind_settings(&self) {
        // Bind setting "button-frame" to "has-frame" property of `button`
        let button = self.imp().button.get();
        self.settings()
            .bind("button-frame", &button, "has-frame")
            .build();

        // Bind setting "orientation" to "orientation" property of `button`
        let gtk_box = self.imp().gtk_box.get();
        self.settings()
            .bind("orientation", &gtk_box, "orientation")
            .mapping(|variant, _| {
                let orientation = variant
                    .get::<String>()
                    .expect("The variant needs to be of type `String`.");

                let orientation = match orientation.as_str() {
                    "Horizontal" => Orientation::Horizontal,
                    "Vertical" => Orientation::Vertical,
                    _ => unreachable!(),
                };

                Some(orientation.to_value())
            })
            .build();
    }
}

由于来自 create_action 的动作遵循上述约定，我们可以尽量减少进一步的改动。每次激活时，"win.button-frame" 动作都会切换其状态，而 "win.orientation" 动作的状态则遵循给定的参数。

不过，我们仍需指定动作激活时应发生的情况。对于有状态的操作，我们不用为它的"激活"信号添加回调，而是将设置绑定到我们要操作的属性上。

文件名：listings/actions/7/window/mod.rs

mod imp;

use gio::{ActionEntry, Settings};
use glib::Object;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Application, Orientation};

use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn setup_actions(&self) {
        // Add stateful action "count" to `window` taking an integer as parameter
        let original_state = 0;
        let action_count = ActionEntry::builder("count")
            .parameter_type(Some(&i32::static_variant_type()))
            .state(original_state.to_variant())
            .activate(move |window: &Self, action, parameter| {
                // Get state
                let mut state = action
                    .state()
                    .expect("Could not get state.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Get parameter
                let parameter = parameter
                    .expect("Could not get parameter.")
                    .get::<i32>()
                    .expect("The variant needs to be of type `i32`.");

                // Increase state by parameter and store state
                state += parameter;
                action.set_state(&state.to_variant());

                // Update label with new state
                window.imp().label.set_label(&format!("Counter: {state}"));
            })
            .build();
        self.add_action_entries([action_count]);

        // Create action from key "button-frame" and add to action group "win"
        let action_button_frame = self.settings().create_action("button-frame");
        self.add_action(&action_button_frame);

        // Create action from key "orientation" and add to action group "win"
        let action_orientation = self.settings().create_action("orientation");
        self.add_action(&action_orientation);
    }

    fn bind_settings(&self) {
        // Bind setting "button-frame" to "has-frame" property of `button`
        let button = self.imp().button.get();
        self.settings()
            .bind("button-frame", &button, "has-frame")
            .build();

        // Bind setting "orientation" to "orientation" property of `button`
        let gtk_box = self.imp().gtk_box.get();
        self.settings()
            .bind("orientation", &gtk_box, "orientation")
            .mapping(|variant, _| {
                let orientation = variant
                    .get::<String>()
                    .expect("The variant needs to be of type `String`.");

                let orientation = match orientation.as_str() {
                    "Horizontal" => Orientation::Horizontal,
                    "Vertical" => Orientation::Vertical,
                    _ => unreachable!(),
                };

                Some(orientation.to_value())
            })
            .build();
    }
}

最后，我们要确保 bind_settings 在构造(constructed)内部被调用。

文件名：listings/actions/7/window/imp.rs

use gio::Settings;
use glib::subclass::InitializingObject;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, Button, CompositeTemplate, Label};
use std::cell::OnceCell;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/example/window.ui")]
pub struct Window {
    #[template_child]
    pub gtk_box: TemplateChild<gtk::Box>,
    #[template_child]
    pub button: TemplateChild<Button>,
    #[template_child]
    pub label: TemplateChild<Label>,
    pub settings: OnceCell<Settings>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "MyGtkAppWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Setup
        let obj = self.obj();
        obj.setup_settings();
        obj.setup_actions();
        obj.bind_settings();
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

动作的功能非常强大，我们在此只是浅尝辄止。如果您想了解更多，GNOME 开发者文档是一个很好的开始。

控制待办事项应用的状态

过滤任务

现在是继续开发待办事项应用的时候了。一个值得添加的功能是：过滤任务。这是一个利用我们新学到的关于 Action 的知识的好机会！使用 Action，我们可以通过菜单和键盘快捷键访问过滤器。这就是我们希望的最终效果：

请注意，屏幕录像还显示了一个标签为"清除(Clear)"的按钮，它将删除所有已完成的任务。当我们以后让应用程序在不同会话之间保存任务时，这个按钮就会派上用场。

让我们先在 window.ui 中添加菜单和标题栏。在阅读了动作一章后，我们应该会对添加的代码感到熟悉。

文件名：listings/todo/2/resources/window.ui

 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <menu id="main-menu">
+    <submenu>
+      <attribute name="label" translatable="yes">_Filter</attribute>
+      <item>
+        <attribute name="label" translatable="yes">_All</attribute>
+        <attribute name="action">win.filter</attribute>
+        <attribute name="target">All</attribute>
+      </item>
+      <item>
+        <attribute name="label" translatable="yes">_Open</attribute>
+        <attribute name="action">win.filter</attribute>
+        <attribute name="target">Open</attribute>
+      </item>
+      <item>
+        <attribute name="label" translatable="yes">_Done</attribute>
+        <attribute name="action">win.filter</attribute>
+        <attribute name="target">Done</attribute>
+      </item>
+    </submenu>
+    <item>
+      <attribute name="label" translatable="yes">_Remove Done Tasks</attribute>
+      <attribute name="action">win.remove-done-tasks</attribute>
+    </item>
+    <item>
+      <attribute name="label" translatable="yes">_Keyboard Shortcuts</attribute>
+      <attribute name="action">win.show-help-overlay</attribute>
+    </item>
+  </menu>
   <template class="TodoWindow" parent="GtkApplicationWindow">
     <property name="width-request">360</property>
     <property name="title" translatable="yes">To-Do</property>
+    <child type="titlebar">
+      <object class="GtkHeaderBar">
+        <child type="end">
+          <object class="GtkMenuButton" id="menu_button">
+            <property name="icon-name">open-menu-symbolic</property>
+            <property name="menu-model">main-menu</property>
+          </object>
+        </child>
+      </object>
+    </child>

然后，我们创建一个设置 schema。同样，"过滤器"设置与菜单调用的有状态的动作（Action）相对应。

文件名：listings/todo/2/org.gtk_rs.Todo2.gschema.xml

<?xml version="1.0" encoding="utf-8"?>
<schemalist>
  <schema id="org.gtk_rs.Todo2" path="/org/gtk_rs/Todo2/">
    <key name="filter" type="s">
      <choices>
        <choice value='All'/>
        <choice value='Open'/>
        <choice value='Done'/>
      </choices>
      <default>'All'</default>
      <summary>Filter of the tasks</summary>
    </key>
  </schema>
</schemalist>

我们按照设置一章中的描述安装 schema. 然后，我们将设置(settings)的引用添加到 imp::Window.

use std::cell::RefCell;
use std::fs::File;

use gio::Settings;
use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, CompositeTemplate, Entry, ListView};
use std::cell::OnceCell;

use crate::task_object::{TaskData, TaskObject};
use crate::utils::data_path;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/Todo2/window.ui")]
pub struct Window {
    #[template_child]
    pub entry: TemplateChild<Entry>,
    #[template_child]
    pub tasks_list: TemplateChild<ListView>,
    pub tasks: RefCell<Option<gio::ListStore>>,
    pub settings: OnceCell<Settings>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "TodoWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();

        // Create action to remove done tasks and add to action group "win"
        klass.install_action("win.remove-done-tasks", None, |window, _, _| {
            window.remove_done_tasks();
        });
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Setup
        let obj = self.obj();
        obj.setup_settings();
        obj.setup_tasks();
        obj.restore_data();
        obj.setup_callbacks();
        obj.setup_factory();
        obj.setup_actions();
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {
    fn close_request(&self) -> glib::Propagation {
        // Store task data in vector
        let backup_data: Vec<TaskData> = self
            .obj()
            .tasks()
            .iter::<TaskObject>()
            .filter_map(Result::ok)
            .map(|task_object| task_object.task_data())
            .collect();

        // Save state to file
        let file = File::create(data_path()).expect("Could not create json file.");
        serde_json::to_writer(file, &backup_data)
            .expect("Could not write data to json file");

        // Pass close request on to the parent
        self.parent_close_request()
    }
}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

同样，我们创建了一些函数，以方便访问设置。

mod imp;

use std::fs::File;

use gio::Settings;
use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{
    gio, glib, Application, CustomFilter, FilterListModel, NoSelection,
    SignalListItemFactory,
};
use gtk::{prelude::*, ListItem};

use crate::task_object::{TaskData, TaskObject};
use crate::task_row::TaskRow;
use crate::utils::data_path;
use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn filter(&self) -> Option<CustomFilter> {
        // Get filter_state from settings
        let filter_state: String = self.settings().get("filter");

        // Create custom filters
        let filter_open = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow completed tasks
            !task_object.is_completed()
        });
        let filter_done = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow done tasks
            task_object.is_completed()
        });

        // Return the correct filter
        match filter_state.as_str() {
            "All" => None,
            "Open" => Some(filter_open),
            "Done" => Some(filter_done),
            _ => unreachable!(),
        }
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with filter and selection and pass it to the list view
        let filter_model = FilterListModel::new(Some(self.tasks()), self.filter());
        let selection_model = NoSelection::new(Some(filter_model.clone()));
        self.imp().tasks_list.set_model(Some(&selection_model));

        // Filter model whenever the value of the key "filter" changes
        self.settings().connect_changed(
            Some("filter"),
            clone!(
                #[weak(rename_to = window)]
                self,
                #[weak]
                filter_model,
                move |_, _| {
                    filter_model.set_filter(window.filter().as_ref());
                }
            ),
        );
    }

    fn restore_data(&self) {
        if let Ok(file) = File::open(data_path()) {
            // Deserialize data from file to vector
            let backup_data: Vec<TaskData> = serde_json::from_reader(file).expect(
                "It should be possible to read `backup_data` from the json file.",
            );

            // Convert `Vec<TaskData>` to `Vec<TaskObject>`
            let task_objects: Vec<TaskObject> = backup_data
                .into_iter()
                .map(TaskObject::from_task_data)
                .collect();

            // Insert restored objects into model
            self.tasks().extend_from_slice(&task_objects);
        }
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }

    fn setup_actions(&self) {
        // Create action from key "filter" and add to action group "win"
        let action_filter = self.settings().create_action("filter");
        self.add_action(&action_filter);
    }

    fn remove_done_tasks(&self) {
        let tasks = self.tasks();
        let mut position = 0;
        while let Some(item) = tasks.item(position) {
            // Get `TaskObject` from `glib::Object`
            let task_object = item
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            if task_object.is_completed() {
                tasks.remove(position);
            } else {
                position += 1;
            }
        }
    }
}

我们还为 TaskObject 添加了 is_completed、task_data 和 from_task_data 方法。我们将在下面的代码段中使用它们。

文件名：listings/todo/2/task_object/mod.rs

mod imp;

use glib::Object;
use gtk::glib;
use gtk::subclass::prelude::*;
use serde::{Deserialize, Serialize};

glib::wrapper! {
    pub struct TaskObject(ObjectSubclass<imp::TaskObject>);
}

impl TaskObject {
    pub fn new(completed: bool, content: String) -> Self {
        Object::builder()
            .property("completed", completed)
            .property("content", content)
            .build()
    }

    pub fn is_completed(&self) -> bool {
        self.imp().data.borrow().completed
    }

    pub fn task_data(&self) -> TaskData {
        self.imp().data.borrow().clone()
    }

    pub fn from_task_data(task_data: TaskData) -> Self {
        Self::new(task_data.completed, task_data.content)
    }
}

#[derive(Default, Clone, Serialize, Deserialize)]
pub struct TaskData {
    pub completed: bool,
    pub content: String,
}

与前一章类似，我们让设置(settings)创建动作。然后，我们将新创建的动作"过滤器(filter)"添加到窗口中。

mod imp;

use std::fs::File;

use gio::Settings;
use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{
    gio, glib, Application, CustomFilter, FilterListModel, NoSelection,
    SignalListItemFactory,
};
use gtk::{prelude::*, ListItem};

use crate::task_object::{TaskData, TaskObject};
use crate::task_row::TaskRow;
use crate::utils::data_path;
use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn filter(&self) -> Option<CustomFilter> {
        // Get filter_state from settings
        let filter_state: String = self.settings().get("filter");

        // Create custom filters
        let filter_open = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow completed tasks
            !task_object.is_completed()
        });
        let filter_done = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow done tasks
            task_object.is_completed()
        });

        // Return the correct filter
        match filter_state.as_str() {
            "All" => None,
            "Open" => Some(filter_open),
            "Done" => Some(filter_done),
            _ => unreachable!(),
        }
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with filter and selection and pass it to the list view
        let filter_model = FilterListModel::new(Some(self.tasks()), self.filter());
        let selection_model = NoSelection::new(Some(filter_model.clone()));
        self.imp().tasks_list.set_model(Some(&selection_model));

        // Filter model whenever the value of the key "filter" changes
        self.settings().connect_changed(
            Some("filter"),
            clone!(
                #[weak(rename_to = window)]
                self,
                #[weak]
                filter_model,
                move |_, _| {
                    filter_model.set_filter(window.filter().as_ref());
                }
            ),
        );
    }

    fn restore_data(&self) {
        if let Ok(file) = File::open(data_path()) {
            // Deserialize data from file to vector
            let backup_data: Vec<TaskData> = serde_json::from_reader(file).expect(
                "It should be possible to read `backup_data` from the json file.",
            );

            // Convert `Vec<TaskData>` to `Vec<TaskObject>`
            let task_objects: Vec<TaskObject> = backup_data
                .into_iter()
                .map(TaskObject::from_task_data)
                .collect();

            // Insert restored objects into model
            self.tasks().extend_from_slice(&task_objects);
        }
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }

    fn setup_actions(&self) {
        // Create action from key "filter" and add to action group "win"
        let action_filter = self.settings().create_action("filter");
        self.add_action(&action_filter);
    }

    fn remove_done_tasks(&self) {
        let tasks = self.tasks();
        let mut position = 0;
        while let Some(item) = tasks.item(position) {
            // Get `TaskObject` from `glib::Object`
            let task_object = item
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            if task_object.is_completed() {
                tasks.remove(position);
            } else {
                position += 1;
            }
        }
    }
}

我们还添加了一个动作，允许我们删除已完成的任务。这次我们使用另一种名为 install_action 的方法。这种方法有一些限制。它只能在子类化部件时使用，而且不支持有状态的动作。但是，它的用法很简洁，而且有一个相应的姊妹方法 install_action_async，我们将在以后的章节中使用它。

use std::cell::RefCell;
use std::fs::File;

use gio::Settings;
use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, CompositeTemplate, Entry, ListView};
use std::cell::OnceCell;

use crate::task_object::{TaskData, TaskObject};
use crate::utils::data_path;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/Todo2/window.ui")]
pub struct Window {
    #[template_child]
    pub entry: TemplateChild<Entry>,
    #[template_child]
    pub tasks_list: TemplateChild<ListView>,
    pub tasks: RefCell<Option<gio::ListStore>>,
    pub settings: OnceCell<Settings>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "TodoWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();

        // Create action to remove done tasks and add to action group "win"
        klass.install_action("win.remove-done-tasks", None, |window, _, _| {
            window.remove_done_tasks();
        });
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Setup
        let obj = self.obj();
        obj.setup_settings();
        obj.setup_tasks();
        obj.restore_data();
        obj.setup_callbacks();
        obj.setup_factory();
        obj.setup_actions();
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {
    fn close_request(&self) -> glib::Propagation {
        // Store task data in vector
        let backup_data: Vec<TaskData> = self
            .obj()
            .tasks()
            .iter::<TaskObject>()
            .filter_map(Result::ok)
            .map(|task_object| task_object.task_data())
            .collect();

        // Save state to file
        let file = File::create(data_path()).expect("Could not create json file.");
        serde_json::to_writer(file, &backup_data)
            .expect("Could not write data to json file");

        // Pass close request on to the parent
        self.parent_close_request()
    }
}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

这是 remove_done_tasks 的实现。我们遍历 gio::ListStore 并删除所有已完成的任务对象。

mod imp;

use std::fs::File;

use gio::Settings;
use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{
    gio, glib, Application, CustomFilter, FilterListModel, NoSelection,
    SignalListItemFactory,
};
use gtk::{prelude::*, ListItem};

use crate::task_object::{TaskData, TaskObject};
use crate::task_row::TaskRow;
use crate::utils::data_path;
use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn filter(&self) -> Option<CustomFilter> {
        // Get filter_state from settings
        let filter_state: String = self.settings().get("filter");

        // Create custom filters
        let filter_open = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow completed tasks
            !task_object.is_completed()
        });
        let filter_done = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow done tasks
            task_object.is_completed()
        });

        // Return the correct filter
        match filter_state.as_str() {
            "All" => None,
            "Open" => Some(filter_open),
            "Done" => Some(filter_done),
            _ => unreachable!(),
        }
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with filter and selection and pass it to the list view
        let filter_model = FilterListModel::new(Some(self.tasks()), self.filter());
        let selection_model = NoSelection::new(Some(filter_model.clone()));
        self.imp().tasks_list.set_model(Some(&selection_model));

        // Filter model whenever the value of the key "filter" changes
        self.settings().connect_changed(
            Some("filter"),
            clone!(
                #[weak(rename_to = window)]
                self,
                #[weak]
                filter_model,
                move |_, _| {
                    filter_model.set_filter(window.filter().as_ref());
                }
            ),
        );
    }

    fn restore_data(&self) {
        if let Ok(file) = File::open(data_path()) {
            // Deserialize data from file to vector
            let backup_data: Vec<TaskData> = serde_json::from_reader(file).expect(
                "It should be possible to read `backup_data` from the json file.",
            );

            // Convert `Vec<TaskData>` to `Vec<TaskObject>`
            let task_objects: Vec<TaskObject> = backup_data
                .into_iter()
                .map(TaskObject::from_task_data)
                .collect();

            // Insert restored objects into model
            self.tasks().extend_from_slice(&task_objects);
        }
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }

    fn setup_actions(&self) {
        // Create action from key "filter" and add to action group "win"
        let action_filter = self.settings().create_action("filter");
        self.add_action(&action_filter);
    }

    fn remove_done_tasks(&self) {
        let tasks = self.tasks();
        let mut position = 0;
        while let Some(item) = tasks.item(position) {
            // Get `TaskObject` from `glib::Object`
            let task_object = item
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            if task_object.is_completed() {
                tasks.remove(position);
            } else {
                position += 1;
            }
        }
    }
}

激活 "win.filter" 操作后，相应的设置将被更改。因此我们需要一个方法，将此设置转换为 gtk::FilterListModel 可以理解的过滤器。可能的状态有 "全部"、"待办"和 "已完成"。对于 "待办"和 "已完成"，我们返回 Some(filter) 。如果状态为 "全部"，则无需过滤任何内容，因此我们返回 None.

mod imp;

use std::fs::File;

use gio::Settings;
use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{
    gio, glib, Application, CustomFilter, FilterListModel, NoSelection,
    SignalListItemFactory,
};
use gtk::{prelude::*, ListItem};

use crate::task_object::{TaskData, TaskObject};
use crate::task_row::TaskRow;
use crate::utils::data_path;
use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn filter(&self) -> Option<CustomFilter> {
        // Get filter_state from settings
        let filter_state: String = self.settings().get("filter");

        // Create custom filters
        let filter_open = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow completed tasks
            !task_object.is_completed()
        });
        let filter_done = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow done tasks
            task_object.is_completed()
        });

        // Return the correct filter
        match filter_state.as_str() {
            "All" => None,
            "Open" => Some(filter_open),
            "Done" => Some(filter_done),
            _ => unreachable!(),
        }
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with filter and selection and pass it to the list view
        let filter_model = FilterListModel::new(Some(self.tasks()), self.filter());
        let selection_model = NoSelection::new(Some(filter_model.clone()));
        self.imp().tasks_list.set_model(Some(&selection_model));

        // Filter model whenever the value of the key "filter" changes
        self.settings().connect_changed(
            Some("filter"),
            clone!(
                #[weak(rename_to = window)]
                self,
                #[weak]
                filter_model,
                move |_, _| {
                    filter_model.set_filter(window.filter().as_ref());
                }
            ),
        );
    }

    fn restore_data(&self) {
        if let Ok(file) = File::open(data_path()) {
            // Deserialize data from file to vector
            let backup_data: Vec<TaskData> = serde_json::from_reader(file).expect(
                "It should be possible to read `backup_data` from the json file.",
            );

            // Convert `Vec<TaskData>` to `Vec<TaskObject>`
            let task_objects: Vec<TaskObject> = backup_data
                .into_iter()
                .map(TaskObject::from_task_data)
                .collect();

            // Insert restored objects into model
            self.tasks().extend_from_slice(&task_objects);
        }
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }

    fn setup_actions(&self) {
        // Create action from key "filter" and add to action group "win"
        let action_filter = self.settings().create_action("filter");
        self.add_action(&action_filter);
    }

    fn remove_done_tasks(&self) {
        let tasks = self.tasks();
        let mut position = 0;
        while let Some(item) = tasks.item(position) {
            // Get `TaskObject` from `glib::Object`
            let task_object = item
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            if task_object.is_completed() {
                tasks.remove(position);
            } else {
                position += 1;
            }
        }
    }
}

现在，我们可以设置模型了。通过调用 filter 方法，用设置中的状态初始化 filter_model。每当关键字 "filter" 的状态发生变化时，我们就会再次调用 filter 方法来获取更新后的 filter_model.

mod imp;

use std::fs::File;

use gio::Settings;
use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{
    gio, glib, Application, CustomFilter, FilterListModel, NoSelection,
    SignalListItemFactory,
};
use gtk::{prelude::*, ListItem};

use crate::task_object::{TaskData, TaskObject};
use crate::task_row::TaskRow;
use crate::utils::data_path;
use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn filter(&self) -> Option<CustomFilter> {
        // Get filter_state from settings
        let filter_state: String = self.settings().get("filter");

        // Create custom filters
        let filter_open = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow completed tasks
            !task_object.is_completed()
        });
        let filter_done = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow done tasks
            task_object.is_completed()
        });

        // Return the correct filter
        match filter_state.as_str() {
            "All" => None,
            "Open" => Some(filter_open),
            "Done" => Some(filter_done),
            _ => unreachable!(),
        }
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with filter and selection and pass it to the list view
        let filter_model = FilterListModel::new(Some(self.tasks()), self.filter());
        let selection_model = NoSelection::new(Some(filter_model.clone()));
        self.imp().tasks_list.set_model(Some(&selection_model));

        // Filter model whenever the value of the key "filter" changes
        self.settings().connect_changed(
            Some("filter"),
            clone!(
                #[weak(rename_to = window)]
                self,
                #[weak]
                filter_model,
                move |_, _| {
                    filter_model.set_filter(window.filter().as_ref());
                }
            ),
        );
    }

    fn restore_data(&self) {
        if let Ok(file) = File::open(data_path()) {
            // Deserialize data from file to vector
            let backup_data: Vec<TaskData> = serde_json::from_reader(file).expect(
                "It should be possible to read `backup_data` from the json file.",
            );

            // Convert `Vec<TaskData>` to `Vec<TaskObject>`
            let task_objects: Vec<TaskObject> = backup_data
                .into_iter()
                .map(TaskObject::from_task_data)
                .collect();

            // Insert restored objects into model
            self.tasks().extend_from_slice(&task_objects);
        }
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }

    fn setup_actions(&self) {
        // Create action from key "filter" and add to action group "win"
        let action_filter = self.settings().create_action("filter");
        self.add_action(&action_filter);
    }

    fn remove_done_tasks(&self) {
        let tasks = self.tasks();
        let mut position = 0;
        while let Some(item) = tasks.item(position) {
            // Get `TaskObject` from `glib::Object`
            let task_object = item
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            if task_object.is_completed() {
                tasks.remove(position);
            } else {
                position += 1;
            }
        }
    }
}

然后，我们使用 set_accels_for_action 将快捷方式与其动作绑定。这里也使用了详细的动作名称。由于这必须在应用程序级别完成，setup_shortcuts 将 gtk::Application 作为参数。

文件名：listings/todo/2/main.rs

mod task_object;
mod task_row;
mod utils;
mod window;

use gtk::prelude::*;
use gtk::{gio, glib, Application};
use window::Window;

const APP_ID: &str = "org.gtk_rs.Todo2";

fn main() -> glib::ExitCode {
    // Register and include resources
    gio::resources_register_include!("todo_2.gresource")
        .expect("Failed to register resources.");

    // Create a new application
    let app = Application::builder().application_id(APP_ID).build();

    // Connect to signals
    app.connect_startup(setup_shortcuts);
    app.connect_activate(build_ui);

    // Run the application
    app.run()
}

fn setup_shortcuts(app: &Application) {
    app.set_accels_for_action("win.filter('All')", &["<Ctrl>a"]);
    app.set_accels_for_action("win.filter('Open')", &["<Ctrl>o"]);
    app.set_accels_for_action("win.filter('Done')", &["<Ctrl>d"]);
}

fn build_ui(app: &Application) {
    // Create a new custom window and present it
    let window = Window::new(app);
    window.present();
}

现在，我们创建了所有这些漂亮的快捷方式，我们希望用户能找到它们。为此，我们需要创建一个快捷方式窗口。我们再次使用一个 ui 文件来描述它，但这里我们不想使用它作为我们自定义控件模板。相反，我们用它实例化了一个现有类 gtk::ShortcutsWindow 的控件。

文件名：listings/todo/2/resources/shortcuts.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <object class="GtkShortcutsWindow" id="help_overlay">
    <property name="modal">True</property>
    <child>
      <object class="GtkShortcutsSection">
        <property name="section-name">shortcuts</property>
        <property name="max-height">10</property>
        <child>
          <object class="GtkShortcutsGroup">
            <property name="title" translatable="yes" context="shortcut window">General</property>
            <child>
              <object class="GtkShortcutsShortcut">
                <property name="title" translatable="yes" context="shortcut window">Show shortcuts</property>
                <property name="action-name">win.show-help-overlay</property>
              </object>
            </child>
            <child>
              <object class="GtkShortcutsShortcut">
                <property name="title" translatable="yes" context="shortcut window">Filter to show all tasks</property>
                <property name="action-name">win.filter('All')</property>
              </object>
            </child>
            <child>
              <object class="GtkShortcutsShortcut">
                <property name="title" translatable="yes" context="shortcut window">Filter to show only open tasks</property>
                <property name="action-name">win.filter('Open')</property>
              </object>
            </child>
            <child>
              <object class="GtkShortcutsShortcut">
                <property name="title" translatable="yes" context="shortcut window">Filter to show only completed tasks</property>
                <property name="action-name">win.filter('Done')</property>
              </object>
            </child>
          </object>
        </child>
      </object>
    </child>
  </object>
</interface>

这些条目可以用 gtk::ShortcutsSection 和 gtk::ShortcutsGroup 来组织。如果我们指定了动作名称，我们就不必重复键盘快键键。 gtk::ShortcutsShortcut 会自行查找。

请注意我们为 ShortcutsShortcut 设置 action-name 的方式。我们没有为目标使用单独的属性，而是使用了一个详细的操作名称。详细名称看上去类似： action_group.action_name(target). 目标的格式取决于其类型，此处有相关说明。尤其是字符串，必须用单引号括起来，如本例所示。

最后，我们必须将 shortcuts.ui 添加到资源中。请注意，我们给它起的别名是 gtk/help-overlay.ui. 这样做是为了利用此处记录的一个便利功能。它将在 gtk/help-overlay.ui 中查找资源，该资源定义了一个 ID 为 help_overlay 的快捷方式窗口(ShortcutsWindow)。如果能找到，它将创建一个操作 win.show-help-overlay 来显示该窗口，并将快捷键 Ctrl + ? 与之关联。

文件名：listings/todo/2/resources/resources.gresource.xml

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/org/gtk_rs/Todo2/">
    <file compressed="true" preprocess="xml-stripblanks" alias="gtk/help-overlay.ui">shortcuts.ui</file>
    <file compressed="true" preprocess="xml-stripblanks">task_row.ui</file>
    <file compressed="true" preprocess="xml-stripblanks">window.ui</file>
  </gresource>
</gresources>

保存和恢复任务

由于我们使用的是设置(Settings)，因此我们的过滤器状态将在会话之间持续存在。但是，任务本身不会。让我们来实现这一点。我们可以将任务存储在设置中，但这样会很不方便。说到序列化和反序列化，没有什么比 serde更好的了。结合 serde_json，我们可以将任务保存为序列化的 json 文件。

首先，我们使用 serde 和 serde_json crate 扩展 Cargo.toml.

cargo add serde --features derive
cargo add serde_json

文件名：listings/Cargo.toml

[dependencies]
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"

Serde 是一个用于序列化和反序列化 Rust 数据结构的框架。通过派生（derive）功能，我们只需一行代码就能使我们的结构（去）序列化。我们还使用了 rc 功能，这样 Serde 就能处理 std::rc::Rc 对象。这就是为什么我们将 TodoObject 的数据存储在一个不同的 TodoData 结构中。这样我们就可以为 TodoData 派生出序列化(Serialize)和反序列化(Deserialize).

文件名：listings/todo/2/task_object/mod.rs

mod imp;

use glib::Object;
use gtk::glib;
use gtk::subclass::prelude::*;
use serde::{Deserialize, Serialize};

glib::wrapper! {
    pub struct TaskObject(ObjectSubclass<imp::TaskObject>);
}

impl TaskObject {
    pub fn new(completed: bool, content: String) -> Self {
        Object::builder()
            .property("completed", completed)
            .property("content", content)
            .build()
    }

    pub fn is_completed(&self) -> bool {
        self.imp().data.borrow().completed
    }

    pub fn task_data(&self) -> TaskData {
        self.imp().data.borrow().clone()
    }

    pub fn from_task_data(task_data: TaskData) -> Self {
        Self::new(task_data.completed, task_data.content)
    }
}

#[derive(Default, Clone, Serialize, Deserialize)]
pub struct TaskData {
    pub completed: bool,
    pub content: String,
}

我们计划将数据存储为文件，因此我们创建了一个工具函数，为我们提供合适的文件路径。我们使用 glib::user_config_dir 获取配置目录的路径，并为应用程序创建一个新的子目录。然后返回文件路径。

文件名：listings/todo/2/utils.rs

use std::path::PathBuf;

use gtk::glib;

use crate::APP_ID;

pub fn data_path() -> PathBuf {
    let mut path = glib::user_data_dir();
    path.push(APP_ID);
    std::fs::create_dir_all(&path).expect("Could not create directory.");
    path.push("data.json");
    path
}

我们重写了 close_request 虚函数，以便在窗口关闭时保存任务。为此，我们首先遍历所有条目并将其存储在一个 Vec 中。然后将 Vec 序列化，并将数据存储为 json 文件。

use std::cell::RefCell;
use std::fs::File;

use gio::Settings;
use glib::subclass::InitializingObject;
use gtk::prelude::*;
use gtk::subclass::prelude::*;
use gtk::{gio, glib, CompositeTemplate, Entry, ListView};
use std::cell::OnceCell;

use crate::task_object::{TaskData, TaskObject};
use crate::utils::data_path;

// Object holding the state
#[derive(CompositeTemplate, Default)]
#[template(resource = "/org/gtk_rs/Todo2/window.ui")]
pub struct Window {
    #[template_child]
    pub entry: TemplateChild<Entry>,
    #[template_child]
    pub tasks_list: TemplateChild<ListView>,
    pub tasks: RefCell<Option<gio::ListStore>>,
    pub settings: OnceCell<Settings>,
}

// The central trait for subclassing a GObject
#[glib::object_subclass]
impl ObjectSubclass for Window {
    // `NAME` needs to match `class` attribute of template
    const NAME: &'static str = "TodoWindow";
    type Type = super::Window;
    type ParentType = gtk::ApplicationWindow;

    fn class_init(klass: &mut Self::Class) {
        klass.bind_template();

        // Create action to remove done tasks and add to action group "win"
        klass.install_action("win.remove-done-tasks", None, |window, _, _| {
            window.remove_done_tasks();
        });
    }

    fn instance_init(obj: &InitializingObject<Self>) {
        obj.init_template();
    }
}

// Trait shared by all GObjects
impl ObjectImpl for Window {
    fn constructed(&self) {
        // Call "constructed" on parent
        self.parent_constructed();

        // Setup
        let obj = self.obj();
        obj.setup_settings();
        obj.setup_tasks();
        obj.restore_data();
        obj.setup_callbacks();
        obj.setup_factory();
        obj.setup_actions();
    }
}

// Trait shared by all widgets
impl WidgetImpl for Window {}

// Trait shared by all windows
impl WindowImpl for Window {
    fn close_request(&self) -> glib::Propagation {
        // Store task data in vector
        let backup_data: Vec<TaskData> = self
            .obj()
            .tasks()
            .iter::<TaskObject>()
            .filter_map(Result::ok)
            .map(|task_object| task_object.task_data())
            .collect();

        // Save state to file
        let file = File::create(data_path()).expect("Could not create json file.");
        serde_json::to_writer(file, &backup_data)
            .expect("Could not write data to json file");

        // Pass close request on to the parent
        self.parent_close_request()
    }
}

// Trait shared by all application windows
impl ApplicationWindowImpl for Window {}

让我们来看看 Vec<TaskData> 将被序列化成什么样子。请注意，serde_json::to_writer 会以更简洁但可读性更差的方式保存数据。若要创建等价但格式友好的 json，只需将 to_writer 替换为 serde_json::to_writer_pretty.

文件名：data.json

[
  {
    "completed": true,
    "content": "Task Number Two"
  },
  {
    "completed": false,
    "content": "Task Number Five"
  },
  {
    "completed": true,
    "content": "Task Number Six"
  },
  {
    "completed": false,
    "content": "Task Number Seven"
  },
  {
    "completed": false,
    "content": "Task Number Eight"
  }
]

当我们启动应用程序时，我们希望恢复已保存的数据。让我们为此添加一个 restore_data 方法。我们将确保处理启动时没有数据文件的情况。这可能是我们第一次启动应用程序，因此没有以前的会话可以恢复。

mod imp;

use std::fs::File;

use gio::Settings;
use glib::{clone, Object};
use gtk::subclass::prelude::*;
use gtk::{
    gio, glib, Application, CustomFilter, FilterListModel, NoSelection,
    SignalListItemFactory,
};
use gtk::{prelude::*, ListItem};

use crate::task_object::{TaskData, TaskObject};
use crate::task_row::TaskRow;
use crate::utils::data_path;
use crate::APP_ID;

glib::wrapper! {
    pub struct Window(ObjectSubclass<imp::Window>)
        @extends gtk::ApplicationWindow, gtk::Window, gtk::Widget,
        @implements gio::ActionGroup, gio::ActionMap, gtk::Accessible, gtk::Buildable,
                    gtk::ConstraintTarget, gtk::Native, gtk::Root, gtk::ShortcutManager;
}

impl Window {
    pub fn new(app: &Application) -> Self {
        // Create new window
        Object::builder().property("application", app).build()
    }

    fn setup_settings(&self) {
        let settings = Settings::new(APP_ID);
        self.imp()
            .settings
            .set(settings)
            .expect("`settings` should not be set before calling `setup_settings`.");
    }

    fn settings(&self) -> &Settings {
        self.imp()
            .settings
            .get()
            .expect("`settings` should be set in `setup_settings`.")
    }

    fn tasks(&self) -> gio::ListStore {
        // Get state
        self.imp()
            .tasks
            .borrow()
            .clone()
            .expect("Could not get current tasks.")
    }

    fn filter(&self) -> Option<CustomFilter> {
        // Get filter_state from settings
        let filter_state: String = self.settings().get("filter");

        // Create custom filters
        let filter_open = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow completed tasks
            !task_object.is_completed()
        });
        let filter_done = CustomFilter::new(|obj| {
            // Get `TaskObject` from `glib::Object`
            let task_object = obj
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            // Only allow done tasks
            task_object.is_completed()
        });

        // Return the correct filter
        match filter_state.as_str() {
            "All" => None,
            "Open" => Some(filter_open),
            "Done" => Some(filter_done),
            _ => unreachable!(),
        }
    }

    fn setup_tasks(&self) {
        // Create new model
        let model = gio::ListStore::new::<TaskObject>();

        // Get state and set model
        self.imp().tasks.replace(Some(model));

        // Wrap model with filter and selection and pass it to the list view
        let filter_model = FilterListModel::new(Some(self.tasks()), self.filter());
        let selection_model = NoSelection::new(Some(filter_model.clone()));
        self.imp().tasks_list.set_model(Some(&selection_model));

        // Filter model whenever the value of the key "filter" changes
        self.settings().connect_changed(
            Some("filter"),
            clone!(
                #[weak(rename_to = window)]
                self,
                #[weak]
                filter_model,
                move |_, _| {
                    filter_model.set_filter(window.filter().as_ref());
                }
            ),
        );
    }

    fn restore_data(&self) {
        if let Ok(file) = File::open(data_path()) {
            // Deserialize data from file to vector
            let backup_data: Vec<TaskData> = serde_json::from_reader(file).expect(
                "It should be possible to read `backup_data` from the json file.",
            );

            // Convert `Vec<TaskData>` to `Vec<TaskObject>`
            let task_objects: Vec<TaskObject> = backup_data
                .into_iter()
                .map(TaskObject::from_task_data)
                .collect();

            // Insert restored objects into model
            self.tasks().extend_from_slice(&task_objects);
        }
    }

    fn setup_callbacks(&self) {
        // Setup callback for activation of the entry
        self.imp().entry.connect_activate(clone!(
            #[weak(rename_to = window)]
            self,
            move |_| {
                window.new_task();
            }
        ));

        // Setup callback for clicking (and the releasing) the icon of the entry
        self.imp().entry.connect_icon_release(clone!(
            #[weak(rename_to = window)]
            self,
            move |_, _| {
                window.new_task();
            }
        ));
    }

    fn new_task(&self) {
        // Get content from entry and clear it
        let buffer = self.imp().entry.buffer();
        let content = buffer.text().to_string();
        if content.is_empty() {
            return;
        }
        buffer.set_text("");

        // Add new task to model
        let task = TaskObject::new(false, content);
        self.tasks().append(&task);
    }

    fn setup_factory(&self) {
        // Create a new factory
        let factory = SignalListItemFactory::new();

        // Create an empty `TaskRow` during setup
        factory.connect_setup(move |_, list_item| {
            // Create `TaskRow`
            let task_row = TaskRow::new();
            list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .set_child(Some(&task_row));
        });

        // Tell factory how to bind `TaskRow` to a `TaskObject`
        factory.connect_bind(move |_, list_item| {
            // Get `TaskObject` from `ListItem`
            let task_object = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .item()
                .and_downcast::<TaskObject>()
                .expect("The item has to be an `TaskObject`.");

            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.bind(&task_object);
        });

        // Tell factory how to unbind `TaskRow` from `TaskObject`
        factory.connect_unbind(move |_, list_item| {
            // Get `TaskRow` from `ListItem`
            let task_row = list_item
                .downcast_ref::<ListItem>()
                .expect("Needs to be ListItem")
                .child()
                .and_downcast::<TaskRow>()
                .expect("The child has to be a `TaskRow`.");

            task_row.unbind();
        });

        // Set the factory of the list view
        self.imp().tasks_list.set_factory(Some(&factory));
    }

    fn setup_actions(&self) {
        // Create action from key "filter" and add to action group "win"
        let action_filter = self.settings().create_action("filter");
        self.add_action(&action_filter);
    }

    fn remove_done_tasks(&self) {
        let tasks = self.tasks();
        let mut position = 0;
        while let Some(item) = tasks.item(position) {
            // Get `TaskObject` from `glib::Object`
            let task_object = item
                .downcast_ref::<TaskObject>()
                .expect("The object needs to be of type `TaskObject`.");

            if task_object.is_completed() {
                tasks.remove(position);
            } else {
                position += 1;
            }
        }
    }
}

最后，我们要确保一切在 constructed 中配置好。