Question

I am having troubles displaying my pop-up from inside a different thread. I have tried reading some of the other questions on here, but I can’t see to understand how I can apply them…

I have an app that uses the camera, and I want to pop up a preview of the picture after its available.

The PhotoCamera has the event ‘CaptureImageAvailable’ and in there I want to pop-up the preview

private void cam_CaptureImageAvailable(object sender, ContentReadyEventArgs e)
    {
        BitmapImage img = new BitmapImage();
        img.SetSource(e.ImageStream);
        e.ImageStream.Close();

        //creating the new pop-up preview
        Grid panelPreview = new Grid();
        panelPreview.Background = new SolidColorBrush(Colors.Black);
        panelPreview.Width = 300;
        panelPreview.Height = 400;

        //create an ImageBrush to display the image in the new pop-up
        ImageBrush imgPreview = new ImageBrush();
        imgPreview.ImageSource = img;

        //need a rectangle to add the image to, otherwise can't add it
        Rectangle rect = new Rectangle();
        rect.Width = 300;
        rect.Height = 400;
        rect.Fill = imgPreview;

        //Adding the rectangle to the grid
        panelPreview.Children.Add(rect);

        imagePreview.IsOpen = true;

        ....
    }

This causes an UnauthorizedAcessException, which makes sense to me, because this event is on a different thread, but what I don’t understand is how to fix it… I have tried using this code as well

private void cam_CaptureImageAvailable(object sender, ContentReadyEventArgs e)
    {

        Deployment.Current.Dispatcher.BeginInvoke(delegate()
        {

            BitmapImage img = new BitmapImage();
            img.SetSource(e.ImageStream);
            e.ImageStream.Close();

            //creating the new pop-up preview
            Grid panelPreview = new Grid();
            panelPreview.Background = new SolidColorBrush(Colors.Black);
            panelPreview.Width = 300;
            panelPreview.Height = 400;

            //create an ImageBrush to display the image in the new pop-up
            ImageBrush imgPreview = new ImageBrush();
            imgPreview.ImageSource = img;

            //need a rectangle to add the image to, otherwise can't add it
            Rectangle rect = new Rectangle();
            rect.Width = 300;
            rect.Height = 400;
            rect.Fill = imgPreview;

            //Adding the rectangle to the grid
            panelPreview.Children.Add(rect);

            imagePreview.IsOpen = true;
        });

This method doesn’t throw any errors, but also doesn’t appear to actually do anything. How do I display this pop-up on the UI thread?

Answer 1

What is “imagePreview”?

If it is anykind of popup or image element container than u must add “panelPreview” as it’s child ,so that it become visible on UI.

One more thing, u can use thumbnail image(via

private void cam_CaptureThumbnailAvailable(object sender,
ContentReadyEventArgs e)

) for viewing on popup which will take very less memory than actual image.