Question

I wanted to pause a VideoStream from a Kinect. The button has the following code:

if (capturing==0)
{
    try
    {
        // Signing the Event for Image frame ready
        nuiRuntime.VideoFrameReady += new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_VideoFrameReady);
        nuiRuntime.DepthFrameReady += new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_DepthFrameReady);
        nuiRuntime.VideoStream.Open(ImageStreamType.Video, 2, ImageResolution.Resolution640x480, ImageType.Color);
        nuiRuntime.DepthStream.Open(ImageStreamType.Depth, 2, ImageResolution.Resolution320x240, ImageType.Depth);
    }
    catch
    {
        Dialogs.ShowWarning("An Error occured. Check, if the Kinect is connected properly.");
    }
    finally
    {
        capturing = 2;
    }
}
else if (capturing == 1)
{
    nuiRuntime.VideoFrameReady += new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_VideoFrameReady);
    nuiRuntime.DepthFrameReady += new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_DepthFrameReady);
    capturing = 2;//go on after break 
}
else
{
    nuiRuntime.VideoFrameReady -= new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_VideoFrameReady);
    nuiRuntime.DepthFrameReady -= nuiRuntime_DepthFrameReady;
    capturing = 1;//pause
}

I dont think, it is hard to understand.
States: 0, Kinect is uninitialized, do so
1, Kinect is paused, go on
2, Kinect is normally capturing

But: when the “else” is executed, the Image in the GUI (WPF.Image) still shows a moving video-stream. In the “else” are 2 ways, I tried to make it a break. Then there should be displayed a still picture.

Of course, I simply can say the EventHandler: If we are in state 1, simply don’t work on the picture, but I don´t think, this is a clean way of implementation.

Can anyone see my mistake?

Answer 1

Event handlers are reference types (delegates), the one you add to the event

nuiRuntime.VideoFrameReady += new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_VideoFrameReady);

is not the same one you remove from it:

nuiRuntime.VideoFrameReady -= new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_VideoFrameReady);

The fix is simple, keep the handler instance somewhere:

var handler = new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_VideoFrameReady);

then add/remove the same instance:

nuiRuntime.VideoFrameReady += handler;
nuiRuntime.VideoFrameReady -= handler;

BTW, the code you use in the “else” block:

nuiRuntime.DepthFrameReady -= nuiRuntime_DepthFrameReady;

is the same as:

nuiRuntime.DepthFrameReady -= new EventHandler<ImageFrameReadyEventArgs>(nuiRuntime_DepthFrameReady);

The compiler simple do the new EventHandler<> things for you.