在WPF中显示“等待”屏幕

单线程操作确实会很痛苦,而且它永远不会像你想的那样工作。在WPF中,窗口最终会变黑,程序将变为“无响应”。

我建议使用BackgroundWorker来完成长时间运行的任务。

private void DoWork(object sender, DoWorkEventArgs e)
{
    //Do the long running process
}

private void WorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    //Hide your wait dialog
}

private void StartWork()
{
   //Show your wait dialog
   BackgroundWorker worker = new BackgroundWorker();
   worker.DoWork += DoWork;
   worker.RunWorkerCompleted += WorkerCompleted;
   worker.RunWorkerAsync();
}

这确实是最简单的方法,而不是试图单线程完成。

this thread .

public static void ForceUIToUpdate()
{
  DispatcherFrame frame = new DispatcherFrame();

  Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Render, new DispatcherOperationCallback(delegate(object parameter)
  {
    frame.Continue = false;
    return null;
  }), null);

  Dispatcher.PushFrame(frame);
}

执行一段代码,以与执行实际任务的方法相同的方式同步显示等待消息。只需将这一行放在冗长的过程之前:

Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Normal, (Action)(() => { /* Your code to display a waiting message */ }));

.

注: here .

选项#2

做这件事 桌面应用程序 Application.DoEvents 方法。WPF提供了两种方法来实现类似的结果:

选项#2.1 DispatcherFrame class .

检查一个有点笨重的例子 MSDN :

[SecurityPermissionAttribute(SecurityAction.Demand, Flags = SecurityPermissionFlag.UnmanagedCode)]
public void DoEvents()
{
    DispatcherFrame frame = new DispatcherFrame();
    Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(ExitFrame), frame);
    Dispatcher.PushFrame(frame);
}

public object ExitFrame(object f)
{
    ((DispatcherFrame)f).Continue = false;
    return null;
}

调用空操作

Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Background, (Action)(() => { }));

请参阅讨论,哪一个(2.1或2.2)更好 here

选项#3

当您显示的不是简单的等待消息,而是动画时,它会派上用场。在等待另一个长时间渲染操作完成的同时渲染加载动画是一个问题。基本上,我们需要两个渲染线程。你不能在一个窗口中有多个渲染线程,但你可以将加载动画放在一个有自己渲染线程的新窗口中,使其看起来不像是一个单独的窗口。

下载 从 this github “,但我在网上找不到了),或者看看下面的主要观点:

public partial class LoadingOverlayWindow : Window
{
    /// <summary>
    ///     Launches a loading window in its own UI thread and positions it over <c>overlayedElement</c>.
    /// </summary>
    /// <param name="overlayedElement"> An element for overlaying by the waiting form/message </param>
    /// <returns> A reference to the created window </returns>
    public static LoadingOverlayWindow CreateAsync(FrameworkElement overlayedElement)
    {
        // Get the coordinates where the loading overlay should be shown
        var locationFromScreen = overlayedElement.PointToScreen(new Point(0, 0));

        // Launch window in its own thread with a specific size and position
        var windowThread = new Thread(() =>
            {
                var window = new LoadingOverlayWindow
                    {
                        Left = locationFromScreen.X,
                        Top = locationFromScreen.Y,
                        Width = overlayedElement.ActualWidth,
                        Height = overlayedElement.ActualHeight
                    };
                window.Show();
                window.Closed += window.OnWindowClosed;
                Dispatcher.Run();
            });
        windowThread.SetApartmentState(ApartmentState.STA);
        windowThread.Start();

        // Wait until the new thread has created the window
        while (windowLauncher.Window == null) {}

        // The window has been created, so return a reference to it
        return windowLauncher.Window;
    }

    public LoadingOverlayWindow()
    {
        InitializeComponent();
    }

    private void OnWindowClosed(object sender, EventArgs args)
    {
        Dispatcher.InvokeShutdown();
    }
}

另一种选择是将长时间运行的例程编写为返回的函数 IEnumerable<double>

yield return 30;

例如,这意味着已经完成了30%的路程。然后,您可以使用WPF计时器在“后台”将其作为协作协程执行。

It's described in some detail here, with sample code.