WP7：从墓碑状态恢复应用程序导致应用程序崩溃。 使用Writeablebitmap

Question

I'm using a Writeablebitmap to take a screenshot of a UI element. The code looks like this:

    private void Screenshot(FrameworkElement element, String fileNameLoader)
    {
        try
        {
            WriteableBitmap bmp = new WriteableBitmap(element, null);

            MemoryStream ms = new MemoryStream();
            bmp.SaveJpeg(ms, (int)element.ActualWidth, (int)element.ActualHeight, 0, 100);
            ms.Seek(0, SeekOrigin.Begin);

            MediaLibrary lib = new MediaLibrary();
            String filePath = string.Format(fileNameLoader);
            lib.SavePicture(filePath, ms);                
         }
        catch (Exception exception)
        {
            txtDebug.Text = "There was an error. Could not save. " + exception.ToString();
        }
    }

The issue I am having is that if I press the save button which calls the Screenshot() method, then press the Home button to tombstone the app and finally press the Back button to bring the app back, I get a screen that says "Resuming..." and the app eventually crashes. After doing some debugging I've noticed that the error seems to be caused by the following line of code:

WriteableBitmap bmp = new WriteableBitmap(element, null);

Replacing that line with:

    WriteableBitmap bmp = null;

saves me from the crash but my app does not work as intended (screenshot doesn't work).

Has anyone ever encountered this issue or would know how to fix it? I'm open to any work-around, as long as I can still take a screenshot of a specific UI element.

Answer 1

I can't reproduce error but you may try this:

private void Screenshot(FrameworkElement element, String fileNameLoader)
{
    WriteableBitmap bmp = new WriteableBitmap(element, null);
    using (MemoryStream ms = new MemoryStream())
    {
        bmp.SaveJpeg(ms, (int)element.ActualWidth, (int)element.ActualHeight, 0, 100);
        ms.Seek(0, SeekOrigin.Begin);
        using (MediaLibrary lib = new MediaLibrary())
        {
            String filePath = string.Format(fileNameLoader);
            lib.SavePicture(filePath, ms);
        }
    }
}