Get result from background thread and update to UI thread continuously UWP

Question

I'm working on a project that has to get the frame from the server and display it to UI. So I used this method to get it continuously. But whole the method is running on UI thread so it blocks my UI a little bit. Do we have any way to make all the method that runs on the different thread and return the result to update three lines of code below on UI thread.

Note: I tried to cover all method of Task.Factory.StartNew and three lines below with Dispatcher.RunAsync but no luck. Because the value return is null.

//width = 1280, height = 960 
private async Task DisplayPreviewTwocamera_Camera1(int width, int height)
{
    _isPreviewing = true;
    try
    {
        byte[] buffer;
        SoftwareBitmap softwareBitmap;
        SoftwareBitmapSource _imageSource;
        while (true)
        {
            if (_isMinimize)
            {
                return;
            }
            buffer = await StreamServiceHandler.Instance.GetStreamCamera_First_1();
            if (buffer.Length == 0)
            {
                buffer = null;
                continue;
            }
            softwareBitmap = SoftwareBitmap.CreateCopyFromBuffer(buffer.AsBuffer(), BitmapPixelFormat.Gray8, width, height);
            buffer = null;
            if (softwareBitmap.BitmapPixelFormat != BitmapPixelFormat.Bgra8 ||
                softwareBitmap.BitmapAlphaMode == BitmapAlphaMode.Straight)
            {
                softwareBitmap = SoftwareBitmap.Convert(softwareBitmap, BitmapPixelFormat.Bgra8, BitmapAlphaMode.Premultiplied);
            }
            //three lines of code below need to run in UI thread
            _imageSource = new SoftwareBitmapSource();
            await _imageSource.SetBitmapAsync(softwareBitmap);
            image_TwoCamera_Camera_1.Source = _imageSource;
        }
    }
    catch (Exception exception)
    {
        Debug.WriteLine(exception);
    }
}

Can you post the whole class, or the pat where you make the call to DisplayPreviewTwocamera_Camera1 — Isma, Dec 11 '17 at 08:40
I call it from onNavigateTo() method without await. I just let it fire and forgot — Bui Quang Huy, Dec 11 '17 at 08:53
That's whats blocking the thread then, if you share that part I might be able to provide an example. — Isma, Dec 11 '17 at 08:59

Ferus7 · Answer 1 · 2017-12-11T09:22:20.727

1

The way you can deal with is running the non IU logic in separate thread and then call the UI thread to update it:

await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal,
                () => {
// UI THREAD
 });

edited Dec 11 '17 at 09:22

answered Dec 11 '17 at 09:16

Ferus7

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Get result from background thread and update to UI thread continuously UWP

1 Answers1