Rust开发Slint GUI时，如何正确获取TextEdit的最新文本？

我正在学习Slint和Rust，读取TextEdit组件的文本属性时遇到问题：点击Gen QRNote按钮，初始文本“Pouet”能正常打印，但修改TextEdit内容后再次点击，输出的还是初始值，无法获取编辑后的内容。

我的Slint GUI定义：

import { Button, VerticalBox } from "std-widgets.slint";
import { HorizontalBox, TextEdit } from "std-widgets.slint";

export component AppWindow inherits Window {
    in-out property<int> counter: 42;
    out property<string> thetext: "Pouet";
    callback request-increase-value();
    callback compute-qr-code();
    callback qr-note-edited();
    VerticalBox {
        TextEdit {
            text: thetext;
            width: 300px;
            height: 300px;
            edited => {
                root.qr-note-edited();
            }
        }
        Button {
            text: "Increase value";
            clicked => {
                root.request-increase-value();
            }
        }
        Button {
            text: "Gen QRNote";
            clicked => {
                root.compute-qr-code();
            }
        }
    }
}

Rust的main()函数代码：

slint::include_modules!();

fn main() -> Result<(), slint::PlatformError> {
    let ui = AppWindow::new()?;

    let ui_handle = ui.as_weak();
    ui.on_request_increase_value(move || {
        let ui = ui_handle.unwrap();
        ui.set_counter(ui.get_counter() + 1);
        println!("button pushed");
    });

    let ui_handle = ui.as_weak();
    ui.on_compute_qr_code(move || {
        let ui = ui_handle.unwrap();
        println!("{}",ui.get_thetext());
    });

    let ui_handle = ui.as_weak();
    ui.on_qr_note_edited(move || {
        let ui = ui_handle.unwrap();
        println!("text changed -> {}", ui.get_thetext());
    });

    ui.run()
}

核心问题不是UI引用的问题（你的as_weak()用法是正确的），而是属性绑定的方向错误：

1. 你定义的thetext是out属性，这意味着它只能从组件内部向外传递值，无法接收外部（或TextEdit）的修改。需要改成in-out属性，支持双向传递。
2. 原代码中TextEdit的text只是单向绑定到thetext，TextEdit内容修改后不会同步回thetext，所以你读取的始终是初始值。

有两种修复方式：

方式一：手动同步文本值 #

修改Slint代码：

• 将out property<string> thetext: "Pouet";改为in-out property<string> thetext: "Pouet";
• 在TextEdit的edited回调中，把当前文本同步到thetext属性：

import { Button, VerticalBox } from "std-widgets.slint";
import { HorizontalBox, TextEdit } from "std-widgets.slint";

export component AppWindow inherits Window {
    in-out property<int> counter: 42;
    in-out property<string> thetext: "Pouet";
    callback request-increase-value();
    callback compute-qr-code();
    callback qr-note-edited();
    VerticalBox {
        TextEdit {
            text: thetext;
            width: 300px;
            height: 300px;
            edited => {
                root.thetext = self.text;
                root.qr-note-edited();
            }
        }
        Button {
            text: "Increase value";
            clicked => {
                root.request-increase-value();
            }
        }
        Button {
            text: "Gen QRNote";
            clicked => {
                root.compute-qr-code();
            }
        }
    }
}

方式二：使用双向绑定（更简洁） #

Slint支持双向绑定语法<=>，直接让TextEdit的text和thetext属性双向同步，无需手动在回调里赋值：

import { Button, VerticalBox } from "std-widgets.slint";
import { HorizontalBox, TextEdit } from "std-widgets.slint";

export component AppWindow inherits Window {
    in-out property<int> counter: 42;
    in-out property<string> thetext: "Pouet";
    callback request-increase-value();
    callback compute-qr-code();
    callback qr-note-edited();
    VerticalBox {
        TextEdit {
            text: <=> thetext;
            width: 300px;
            height: 300px;
            edited => {
                root.qr-note-edited();
            }
        }
        Button {
            text: "Increase value";
            clicked => {
                root.request-increase-value();
            }
        }
        Button {
            text: "Gen QRNote";
            clicked => {
                root.compute-qr-code();
            }
        }
    }
}

两种方式修改后，点击Gen QRNote按钮就能正确获取TextEdit中编辑后的文本值了，Rust代码不需要做任何修改。

内容的提问来源于stack exchange，提问作者FabienM