c# - 为什么 UI 元素不在 Button Click 事件处理程序中反射(reflect)它们的状态？

Question

在下面的例子中，我怎样才能得到:

• 按钮为“禁用-灰色”
• 消息说“正在工作......”

同时工作正在完成，而不是之后工作完成？

XAML:

<Window x:Class="TestIsEnabled8938.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <StackPanel Margin="10" HorizontalAlignment="Left">

        <Button x:Name="Button_Refresh" 
                    HorizontalAlignment="Left"  
                    DockPanel.Dock="Top" 
                    Content="Refresh" 
                    Click="Button_Refresh_Click" 
                    Height="25" 
                    Width="200"/>

        <TextBlock x:Name="Message" Text="Button is ready to click."/>
    </StackPanel>
</Window>

代码隐藏:

using System.Windows;
using System.Threading;

namespace TestIsEnabled8938
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
        }

        private void Button_Refresh_Click(object sender, RoutedEventArgs e)
        {
            Message.Text = "working...";
            Button_Refresh.IsEnabled = false;

            //do work
            Thread.Sleep(2000);

            Message.Text = "Button is ready to click again.";
            Button_Refresh.IsEnabled = true;
        }
    }
}

这也行不通:

Dispatcher.Invoke(new Action(() => { Message.Text = "working..."; }));
Dispatcher.Invoke(new Action(() => { Button_Refresh.IsEnabled = false; }));

回答:

感谢 Heinzi，这段代码有效:

using System.Windows;
using System.Threading;
using System.ComponentModel;

namespace TestIsEnabled8938
{
    public partial class Window1 : Window
    {
        BackgroundWorker backgroundWorker;

        public Window1()
        {
            InitializeComponent();

            backgroundWorker = new BackgroundWorker();

            backgroundWorker.DoWork += (sender, args) =>
            {
                Thread.Sleep(3000);
            };

            backgroundWorker.RunWorkerCompleted += (sender, args) =>
            {
                Message.Text = "button is ready to click again";
                Button_Refresh.IsEnabled = true;
            };
        }

        private void Button_Refresh_Click(object sender, RoutedEventArgs e)
        {
            Message.Text = "working...";
            Button_Refresh.IsEnabled = false;
            backgroundWorker.RunWorkerAsync();
        }
    }
}

Answer 1

如果您希望 UI 在任务运行时更新(并保持响应)，您需要使用单独的线程，例如使用 BackgroundWorker。

代码示例(未经测试):

BackgroundWorker bwButtonWorker;

public Window1() {
    InitializeComponent();

    bwButtonWorker = new BackgroundWorker();

    bwButtonWorker.DoWork += (sender, args) => {
        // do your lengthy stuff here -- this happens in a separate thread
        Thread.Sleep(2000);
    }

    bwButtonWorker.RunWorkerCompleted += (sender, args) => {
        // this happens in the UI thread, so you can modify your UI elements here
        Message.Text = "Button is ready to click again.";
        Button_Refresh.IsEnabled = true;
    }
}

private void Button_Refresh_Click(object sender, RoutedEventArgs e)
{
    Message.Text = "working...";
    Button_Refresh.IsEnabled = false;
    bwButtonWorker.RunWorkerAsync();
}