使用 backgroundWorker 和大量动画维护响应式用户界面

Question

我有一个 C# 应用程序（winforms 和 wpf，但对于这个问题我主要关注 winforms 应用程序），其中 backgroundWorker 用于处理数据集，然后调用 ProgressChanged 然后调用表单刷新方法强制重绘。然后根据数据集的当前帧绘制一堆椭圆。

给定的帧可能涉及绘制零到几百个椭圆之间的任意位置。

此外，我还有一个滑块控件，允许用户调整播放速率（基本上是循环内的 thread.sleep 值。）

当用户将睡眠值设置得太低时，有时重绘方法会排队，并且 UI 变得无响应。（这取决于帧中椭圆的数量和计算机的速度。在 UI 上重新绘制延迟是 100%，而不是任何其他处理，这基本上只是增加一个计数器和设置标签文本。)

我希望能够检测排队情况并自动调整速度滑块以适应更大的数据集 and/or 较慢的计算机。我如何判断 UI 线程是否通过多次调用 Map_Paint 得到备份？

当前代码（解释）：

public Map()
{
  InitializeComponent();

  _worker = new BackgroundWorker();
  _worker.DoWork += _worker_DoWork;
  _worker.ProgressChanged += _worker_ProgressChanged;
  _worker.WorkerReportsProgress = true;
}

private void _worker_DoWork(object sender, DoWorkEventArgs e)
{
    _frameCount = _frames.FrameCount();
    // For this specific example, _frameCount may be around 30000-40000
    for (var i = 0; i < _frameCount; i++)
    {
      var f = _frames.Frame(i + 1);
      _worker.ReportProgress(i, f);
      Thread.Sleep(_tickCount);
      _suspend.WaitOne(); // Used to Pause the playback
    }
}
void _worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
  // set some variables according to state and progresspercentage snipped here
  // ...

  // I would like to detect at this point whether the screen repainting is backed up
  // and if so, adjust the value of _tickCount to slow down the program.

  this.Refresh();
}

private void Map_Paint(object sender, PaintEventArgs e)

{
    // Lots of ellipsis drawing stuff here
    // Maybe 0-1000 ellipses drawn per cycle.
}

private void tbSpeed_Scroll(object sender, EventArgs e)
{
  // This is the Scroll event for the slider.
  // Value range is 10-300
  // The slider becomes unresponsive when the UI thread backs up.
  // I'd like to detect the back up and override the value of _tickCount
  _tickCount = tbSpeed.Value;
}

Answer 1

private static object _lock = new object();
private static int _queuedCount = 0;

public Map()
{
  InitializeComponent();

  _worker = new BackgroundWorker();
  _worker.DoWork += _worker_DoWork;
  _worker.ProgressChanged += _worker_ProgressChanged;
  _worker.WorkerReportsProgress = true;
}

private void _worker_DoWork(object sender, DoWorkEventArgs e)
{
    _frameCount = _frames.FrameCount();
    // For this specific example, _frameCount may be around 30000-40000
    for (var i = 0; i < _frameCount; i++)
    {
      var f = _frames.Frame(i + 1);
      lock(_lock)
      {
          _queuedCount++;
      }
      _worker.ReportProgress(i, f);
      Thread.Sleep(_tickCount);
      _suspend.WaitOne(); // Used to Pause the playback
    }
}
void _worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
  if (_queuedCount > 1)
      //now queue is building up

  this.Refresh();
  lock(_lock)
  {
      _queuedCount--;
  }
}

使用 backgroundWorker 和大量动画维护响应式用户界面

Maintain a responsive user interface with backgroundWorker and heavy animation

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