等待UI重新呈现完成 [英] Waiting for UI re-rendering to complete

问题描述

我这里实际上遇到了2个类似的问题，没有运气在网上找到任何东西.

I've actually got 2 similar problems here with no luck finding anything on the web.

问题1:使用BackgroundWorker，我正在完成％的情况下更新了UI，但是我正在使用UserState，因为我想报告百分比的百分比.问题是，根据输入的不同，有时很少会发生更新(每两秒钟一个百分比)，而其他时候却非常快(每秒触发多次更新的小数百分比).在后一种情况下，我遇到了堆栈溢出(无双关语)的问题.我猜测ProgressChanged事件的调用太多了.现在，这是原型代码，我将直接在progressChanged事件中更新TextBlock，而不使用ViewModels，但稍后再讲.不知道这是否可能是问题.有没有一种方法可以让此更改进度的事件被调用，它需要多长时间运行一次，但是要说些类似的话:如果(！mytextblock.IsRendering())mytextblock.text = newPercent;

Problem 1: Using a BackgroundWorker, I am updating the UI with the % done, but I am using the UserState because I want to report fraction of a percent. The problem is, depending on the inputs, sometimes updates happen rarely (a percent every couple seconds) and other times very fast (triggering fractional % updates many times a second). In the latter case, I'm getting a stack overflow (no pun intended) issue. I'm guessing the ProgressChanged event is just getting called too much. This is for now prototype code and I'm updating a TextBlock directly in the progressChanged event and not using ViewModels, but I will later. Not sure if this might be the problem. Is there a way to allow this progress changed event to get called how often it needs to, but say something like: if (!mytextblock.IsRendering()) mytextblock.text = newPercent;

这样，它会在绘制完最后一个数字后立即进行更新.如果跳过百分比，那没关系.

That way it updates just when it's done drawing the last number. If percents get skipped, that's ok.

问题2:这是一个个人项目，在这里我进行屏幕截图，以某种方式对其进行更改，然后在wpf程序中显示更改后的图像，并不断重复.有没有办法说:抓屏编辑图片更新UIWaitForUIToRender//< -------我该怎么做?重复

Problem 2: This is a personal project where I'm taking a screen capture, changing it in some way, then showing the changed image within the wpf program, and repeat continuously. Is there a way to say: GrabScreen EditImage UpdateUI WaitForUIToRender // <------- how do I do this? Repeat

谢谢

推荐答案

 public class TimedAction 
{
    public static void ExecuteWithDelay(Action action, TimeSpan delay)
    {
        var timer = new DispatcherTimer();
        timer.Interval = delay;
        timer.Tag = action;
        timer.Tick += timer_Tick;
        timer.Start();
    }

    static void timer_Tick(object sender, EventArgs e)
    {
        var timer = (DispatcherTimer)sender;
        var action = (Action)timer.Tag;

        action.Invoke();
        timer.Stop();
    }

    public static void ExecuteAfterRendering(Action action)
    {
        ExecuteAfterFrames(action, 3);
    }

    public static void ExecuteAfterFrames(Action action, int frames)
    {
        var timedAction = new TimedAction();
        timedAction._currentAction = action;
        timedAction._framesToWait = frames;
    }

    private Action _currentAction;
    private int _framesToWait;
    private int _currentFrame = 0;
    private TimedAction()
    {
        CompositionTarget.Rendering += CompositionTarget_Rendering;
    }

    private void Dispose()
    {
        CompositionTarget.Rendering -= CompositionTarget_Rendering;
    }

    void CompositionTarget_Rendering(object sender, EventArgs e)
    {
        _currentFrame++;
        if (_currentFrame == _framesToWait)
        {
            _currentAction.Invoke();
            Dispose();
        }
    }

}

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