阻止UI線程，但繼續處理傳入呼叫

Question

我正在為3D建模應用程序開發插件。 對於此應用程序，還有一個我想自動化的第三方插件（渲染引擎）。

我要做的是創建Camera List<Camera> cameraViews ，遍歷所有這些，並告訴渲染引擎開始渲染

foreach ( Camera camera in cameraViews )
{
    // tell the modellingApplication to apply camera
    modellingApplication.ApplyCameraToView(camera);

    // tell the render engine to render the image
    string path = "somePathWhereIWantToSaveTheImage"
    renderEngine.renderCurrentScene(path)

    // .renderCurrentScene() seems to be async, because my code, which is on the UI thread
    // continues... so:

    // make sure that the image is saved before continuing to the next image
    while ( !File.Exists(path) )
    {
        Thread.Sleep(500);
    }
}

但是，這不會起作用。 renderingplugin似乎完成了一些異步工作，但是在進行異步工作時，它正在調用主線程來檢索信息。

我找到了一種解決方法：在調用渲染引擎進行渲染之后，立即調用MessageBox。 這將阻止代碼繼續執行，但異步調用仍將繼續處理。 我知道，這是奇怪的行為。 更奇怪的是，當renderengine完成調用UI線程以獲取信息並繼續自己的過程時，我的MessageBox自動關閉。 使我的代碼繼續進入while循環，以檢查映像是否保存在磁盤上。

foreach ( Camera camera in cameraViews )
{
    // tell the modellingApplication to apply camera
    modellingApplication.ApplyCameraToView(camera);

    // tell the render engine to render the image
    string path = "somePathWhereIWantToSaveTheImage"
    renderEngine.renderCurrentScene(path)

    // .renderCurrentScene() seems to be async, because my code, which is on the UI thread
    // continues... so:

    // show the messagebox, as this will block the code but not the renderengine.. (?)
    MessageBox.Show("Currently processed: " + path);

    // hmm, messagebox gets automatically closed, that's great, but weird...

    // make sure that the image is saved before continuing to the next image
    while ( !File.Exists(path) )
    {
        Thread.Sleep(500);
    }
}

除了消息框部分之外，這真是太好了。 我不想顯示一個消息框，我只是想暫停我的代碼而不阻塞整個線程（因為仍然接受從renderengine到ui線程的調用）。

如果renderengine不異步完成工作，那會容易得多。

Answer 1

我覺得這不是最好的答案，但希望它就是您要尋找的。 這就是您阻止線程繼續的方式。

    // Your UI thread should already have a Dispatcher object. If you do this elsewhere, then you will need your class to inherit DispatcherObject.
    private DispatcherFrame ThisFrame;

    public void Main()
    {
        // Pausing the Thread
        Pause();
    }

    public void Pause()
    {
        ThisFrame = new DispatcherFrame(true);
        Dispatcher.PushFrame(ThisFrame);
    }

    public void UnPause()
    {
        if (ThisFrame != null && ThisFrame.Continue)
        {
             ThisFrame.Continue = false;
             ThisFrame = null;
        }
    }

如果您希望在中間阻塞的同時仍接收該線程並在該線程上執行操作，則可以執行以下操作。 感覺，嗯……有點怪癖，所以不要只復制並粘貼而不確保我在鍵入時沒有犯重大錯誤。 我還沒喝咖啡。

// Used while a work item is processing. If you have something that you want to wait on this process. Or you could use event handlers or something.
private DispatcherFrame CompleteFrame;
// Controls blocking of the thread.
private DispatcherFrame TaskFrame;

// Set to true to stop the task manager.
private bool Close;

// A collection of tasks you want to queue up on this specific thread. 
private List<jTask> TaskCollection;

public void QueueTask(jTask newTask)
{
    //Task Queued.

    lock (TaskCollection) { TaskCollection.Add(newTask); }
    if (TaskFrame != null) { TaskFrame.Continue = false; }
}

// Call this method when you want to start the task manager and let it wait for a task.
private void FireTaskManager()
{
    do
    {
        if (TaskCollection != null)
        {
            if (TaskCollection.Count > 0 && TaskCollection[0] != null) 
            { 
                ProcessWorkItem(TaskCollection[0]);
                lock (TaskCollection) { TaskCollection.RemoveAt(0); }
            }
            else { WaitForTask(); }
        }
    }
    while (!Close);
}

// Call if you are waiting for something to complete.
private void WaitForTask()
{
    if (CompleteFrame != null) { CompleteFrame.Continue = false; }

    // Waiting For Task.

    TaskFrame = new DispatcherFrame(true);
    Dispatcher.PushFrame(TaskFrame);
    TaskFrame = null;
}

/// <summary>
/// Pumping block will release when all queued tasks are complete. 
/// </summary>
private void WaitForComplete()
{
    if (TaskCollection.Count > 0)
    {
        CompleteFrame = new DispatcherFrame(true);
        Dispatcher.PushFrame(CompleteFrame);
        CompleteFrame = null;
    }
}

private void ProcessWorkItem(jTask taskItem)
{
    if (taskItem != null) { object obj = taskItem.Go(); }
}