关于c＃：使用Aforge.NET和Windows Forms时的线程安全性


Thread safety when using Aforge.NET and Windows Forms

本问题已经有最佳答案，请猛点这里访问。

我很难让aforge.net和我的Windows窗体应用程序一起玩。应用程序需要一个位图流来在自定义的PictureBox中显示视频，同时使用相同的流来跟踪使用颜色的对象。

我尝试锁定newframe事件，将图像从videosource复制到临时图像，如下所示，使用监视器。

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//Event for when a frame from the video is ready
videoSource.NewFrame += (s, e) =>
{
    if (System.Threading.Monitor.TryEnter(updaterLock, 20))
    {
        Bitmap old = currentImage;

        currentImage = (Bitmap)e.Frame.Clone();
        currentImage.RotateFlip(RotateFlipType.RotateNoneFlipY);

        if (currentImage != null)
        {
            if (ImageUpdated != null)
                ImageUpdated(this, EventArgs.Empty);

            if (old != null)
            {
                old.Dispose();
                old = null;
            }
        }
        else
            currentImage = old;

        System.Threading.Monitor.Exit(updaterLock);
    }
};

上面的代码是一个类的一部分，该类返回一个单例实例，通过一个属性授予对当前映像的访问权。在这里可以找到整个类。在自定义控件中，按如下方式访问位图(DisplayControl类保存对rgbstream实例(位图流)的引用)：

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Control.DisplayControl.Instance.ImageUpdated += (s, e) => this.Image = Control.DisplayControl.Instance.Bitmap;

访问控件(this.image)的Image属性时引发异常(InvalidOperationException)，其外观如下：

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System.InvalidOperationException was unhandled by user code
  HResult=-2146233079
  Message=Cross-thread operation not valid: Control 'gridControl' accessed from a thread other than the thread it was created on.
  Source=System.Windows.Forms
  StackTrace:
       at System.Windows.Forms.Control.get_Handle()
       at System.Windows.Forms.Control.SetBoundsCore(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
       at System.Windows.Forms.Control.SetBounds(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
       at System.Windows.Forms.Control.set_Size(Size value)
       at SystemInterface.GUI.Controls.OccupancyGridControl.set_Image(Image value) in c:\Users\Stefan\SW505
oot\ProductCode\GUI\Controls\OccupancyGridControl.cs:line 64
       at SystemInterface.GUI.Controls.OccupancyGridControl.<.ctor>b__0(Object s, EventArgs e) in c:\Users\Stefan\SW505
oot\ProductCode\GUI\Controls\OccupancyGridControl.cs:line 207
       at Control.DisplayControl.<.ctor>b__0(Object s, EventArgs e) in c:\Users\Stefan\SW505
oot\ProductCode\Control\DisplayControl.cs:line 36
       at System.EventHandler.Invoke(Object sender, EventArgs e)
       at Services.CameraServices.RgbStream.<.ctor>b__0(Object s, NewFrameEventArgs e) in c:\Users\Stefan\SW505
oot\ProductCode\Services\CameraServices
gbStream.cs:line 121
       at AForge.Video.DirectShow.VideoCaptureDevice.OnNewFrame(Bitmap image)
       at AForge.Video.DirectShow.VideoCaptureDevice.Grabber.BufferCB(Double sampleTime, IntPtr buffer, Int32 bufferLen)
  InnerException:

有什么办法可以解决这个问题吗？谢谢)

相关讨论

我怀疑您的GUI订阅了ImageUpdated事件。将rgbstream方法更改为以下值：

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private RgbStream(VideoCaptureDevice video)
{
    videoSource = video;
    currentImage = null;
    updaterLock = new object();

    if (videoSource == null)
        return;

    //Start the sensor and wait for it to be ready
    videoSource.Start();
    while (!videoSource.IsRunning) { }

    //Event for when a frame from the video is ready
    videoSource.NewFrame += (s, e) =>
    {
        if (System.Threading.Monitor.TryEnter(updaterLock, 20))
        {
            Bitmap old = currentImage;

            currentImage = (Bitmap)e.Frame.Clone();
            currentImage.RotateFlip(RotateFlipType.RotateNoneFlipY);

            if (currentImage != null)
            {
                if (ImageUpdated != null)
                {
                    SynchronizationContext context = SynchronizationContext.Current ?? new SynchronizationContext();
                    context.Send(s =>
                    {
                        ImageUpdated(this, EventArgs.Empty);

                    }, null);
                }

                if (old != null)
                {
                    old.Dispose();
                    old = null;
                }
            }
            else
                currentImage = old;

            System.Threading.Monitor.Exit(updaterLock);
        }
    };
}
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