问多线程: ThreadPool和显示图像异常
EN

Stack Overflow用户

提问于 2014-11-04 13:13:22

回答 1查看 93关注 0票数 0

我必须在一个新的线程中显示图像序列，否则kinect会因为操作的复杂性而丢失帧。我已经尝试过了：

 using (BodyFrame bodyframe = e.FrameReference.AcquireFrame())
            {
                if (bodyframe != null)
                {
                    if (this.bodies == null)
                    {
                        this.bodies = new Body[bodyframe.BodyCount];
                    }
                    //the first time getandrefreshbodydata is called, kinect will allocate each body in the array.
                    //as long as those body objects are not disposed and not set to null in the array,
                    //those body objects will be re-used.
                    bodyframe.GetAndRefreshBodyData(this.bodies);
                    dataReceived = true;
                }
                else Console.WriteLine();
            }
            BodyCustom[] bodiesCustom = deserialize(directoryTxt[frameCount]);

            sw.WriteLine("Frame " + frameCount);
            if (dataReceived)
            {
                sw.WriteLine(dataReceived);
                ThreadPool.QueueUserWorkItem(showImage, frameCount);
..............

和：

private void showImage(Object frameCount)
    {

       imageReference.Source = new BitmapImage(new Uri(@directoryJpg[(int)frameCount]));
    }

但我有

An unhandled exception of type 'System.InvalidOperationException' occurred in WindowsBase.dll 
Additional information: Unable to access the object from the calling thread because that object is owned by another thread.

我认为错误取决于对象imageReference，因为我在其他地方使用了它，但也通过注释它获得了这个错误。为什么？

我正在使用图像类(System.Windows.Controls)

multithreading

exception

threadpool

kinect

回答 1

Stack Overflow用户

发布于 2014-11-04 13:26:35

问题是你不能在后台线程上更新UI。(如果你把错误消息翻译成英语也会有帮助，我想说这里的大多数人都不懂意大利语。)

您需要重新编组到UI线程上才能更改图像。

首先，您需要存储当前的同步上下文。

这在构造函数中是最简单的。

public class MyObject 
{
  private SynchronizationContext CurrentSynchronizationContext;

  public MyObject()
  { 
    CurrentSynchronizationContext = System.Threading.SynchronizationContext.Current;
  }
}

接下来，在您的ThreadPool.QueueUserWorkItem操作(无论是委托还是lambda)中，添加如下内容：

public void SomeMethodThatDoesSomethingOnABackgroundThread()
{
  ThreadPool.QueueUserWorkItem(() => 
  { 
    // Do some operation that is going to take some time, or can't be done on the UI thread.
    Thread.Sleep(100000); 

    // Operation is complete, let's return the result back to the UI.
    CurrentSynchronizationContext.Post(() => 
    {
      // Change the UI, send a messagebox to the user, change the image. Whatever you need.
      // Also the return isn't necessary, it's just signifying that the method is done. 
      return; 
    },null); 
  }
}