WPF是否可以有多个GUI线程? [英] Can/Does WPF have multiple GUI threads?

问题描述

WPF是否可以有多个GUI线程?还是总是只有一个GUI线程(即使我有多个Windows/对话框)?

Can/Does WPF have multiple GUI threads? Or does it always only have one GUI thread (even if I have multiple windows/dialogs)?

我之所以问是因为我有来自其他线程的事件，并且我想在GUI线程中处理它们(因为我需要根据事件来修改主窗口的控件).

I'm asking because I have events coming from other threads and I'd like to handle them in the GUI thread (because I need to modify the controls of my main window accordings to the events).

顺便说一句:我知道我需要为此使用Dispatcher对象.因此，我可以重新提问一下:WPF中的所有GUI元素始终只有一个Dispatcher对象吗?

Btw: I know I need to use a Dispatcher object for this purpose. So, I could rephrase my question and ask: Is there always only one Dispatcher object for all GUI elements in WPF?

推荐答案

基于第一个答案中的链接，我自己进行了一些验证.我想在这里分享结果.首先:

Based on the link in the first answer I did some verification on my own. I'd like to share the results here. First of all:

可以有多个GUI线程(因此有多个Dispatcher实例).

There can be multiple GUI threads (and therefor multiple Dispatcher instances).

但是:

仅创建一个新窗口(是否有模式)不会创建一个新的GUI线程.一个人需要显式创建该线程(通过创建一个新的Thread).

Simply creating a new window (modal or not) does not create a new GUI thread. One needs to create the thread explicitly (by creating a new instance of Thread).

注意:代替使用单独的线程，模态对话框很可能通过使用

Note: Instead of using separate threads, modal dialogs are likely being realized by using Dispatcher.PushFrame() which blocks the caller of this method while still allowing events to be dispatched.

我创建了一个简单的WPF类(同样，基于第一个答案的链接)来验证所有这些内容.我在这里分享它，以便您可以尝试一下.

I've created a simple WPF class (again, based on the link from the first answer) to verify all this stuff. I share it here so you can play around with it a little bit.

MainWindow.xaml:

MainWindow.xaml:

<Window x:Class="WindowThreadingTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Width="250" Height="130">
  <StackPanel>
    <StackPanel Orientation="Horizontal">
      <TextBlock Text="Thread's ID is "/>
      <TextBlock x:Name="m_threadId"/>
    </StackPanel>
    <StackPanel Orientation="Horizontal">
      <TextBlock Text="Thread's threading apartment is "/>
      <TextBlock x:Name="m_threadTA"/>
    </StackPanel>
    <Button Click="OnCreateNewWindow" Content="Open New Window"/>
    <Button Click="OnAccessTest" Content="Access Test"/>
  </StackPanel>
</Window>

MainWindow.xaml.cs:

MainWindow.xaml.cs:

using System;
using System.Threading;
using System.Windows;
using System.Windows.Media;

namespace WindowThreadingTest {
  /// <summary>
  /// Interaction logic for MainWindow.xaml
  /// </summary>
  public partial class MainWindow : Window {
    private static uint s_windowNumber = 0;

    private readonly MainWindow m_prevWindow;

    public MainWindow() : this(null) { }

    public MainWindow(MainWindow prevWindow) {
      InitializeComponent();

      this.m_prevWindow = prevWindow;

      this.Title = String.Format("Window {0}", ++s_windowNumber);

      Thread thread = Thread.CurrentThread;
      this.m_threadId.Text = thread.ManagedThreadId.ToString();
      this.m_threadTA.Text = thread.GetApartmentState().ToString();
    }

    private void OnCreateNewWindow(object sender, RoutedEventArgs e) {
      CreateNewWindow(true, false, true);
    }

    private void CreateNewWindow(bool newThread, bool modal, bool showInTaskbar) {
      MainWindow mw = this;

      if (newThread) {
        Thread thread = new Thread(() => {
          MainWindow w = new MainWindow(this);
          w.ShowInTaskbar = showInTaskbar;

          if (modal) {
            // ShowDialog automatically starts the event queue for the new windows in the new thread. The window isn't
            // modal though.
            w.ShowDialog();
          } else {
            w.Show();
            w.Closed += (sender2, e2) => w.Dispatcher.InvokeShutdown();
            System.Windows.Threading.Dispatcher.Run();
          }
        });

        thread.SetApartmentState(ApartmentState.STA);
        thread.Start();

      } else {
        MainWindow w = new MainWindow(this);
        w.ShowInTaskbar = showInTaskbar;
        if (modal) {
          // Even modal dialogs run in the same thread.
          w.ShowDialog();
        } else {
          w.Show();
        }
      }
    }

    private void OnAccessTest(object sender, RoutedEventArgs e) {
      if (m_prevWindow == null) {
        return;
      }

      this.Background = Brushes.Lavender;
      try {
        m_prevWindow.Background = Brushes.LightBlue;
      } catch (InvalidOperationException excpt) {
        MessageBox.Show("Exception: " + excpt.Message, "Invalid Operation");
      }
      m_prevWindow.Dispatcher.Invoke((Action)(() => m_prevWindow.Background = Brushes.Green));

      this.Dispatcher.Invoke((Action)(() => {
        try {
          m_prevWindow.Background = Brushes.Red;
        } catch (InvalidOperationException excpt) {
          MessageBox.Show("Exception: " + excpt.Message, "Invalid Dispatcher Operation");
        }
      }));
    }
  }
}

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