Windows Phone - update live tile from background agent with custom image - windows-phone-7

Question

I am trying to add cloud image to album cover if the cover is loaded from internet. I am trying to do this in Background Audio agent and I think I almost got it. The problem is that I have black image in tile. Few times when testing I got cover image with my cloud image in it but mostly I get black image (and sometimes black image with cloud in it).
Can anyone help me find the problem? Thanks
private void UpdateAppTile()
{
var apptile = ShellTile.ActiveTiles.First();
if (apptile != null && _playList != null && _playList.Any())
{
var track = _playList[currentTrackNumber];
var size = 360;
Uri coverUrl;
if (track.AlbumArt.OriginalString.StartsWith("http"))
{
BitmapImage img = null;
using (AutoResetEvent are = new AutoResetEvent(false))
{
string filename = Path.GetFileNameWithoutExtension(track.AlbumArt.OriginalString);
var urlToNewCover = String.Format("http://.../{0}/{1}", filename, size);
coverUrl = new Uri(urlToNewCover, UriKind.Absolute);
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
img = new BitmapImage(coverUrl);
are.Set();
});
are.WaitOne();
var wbmp = CreateTileImageWithCloud(img);
SaveTileImage(wbmp, "/shared/shellcontent/test.jpg");
coverUrl = new Uri("isostore:/shared/shellcontent/test.jpg", UriKind.RelativeOrAbsolute);
}
}
else
{
var coverId = track.Tag.Split(',')[1];
var urlToNewCover = String.Format("http://.../{0}/{1}", coverId, size);
coverUrl = new Uri(urlToNewCover, UriKind.Absolute);
}
var appTileData = new FlipTileData
{
BackgroundImage = coverUrl,
WideBackgroundImage = coverUrl,
...
}
apptile.Update(appTileData);
}
}
public static BitmapImage LoadBitmap(string iFilename)
{
Uri imgUri = new Uri(iFilename, UriKind.Relative);
StreamResourceInfo imageResource = Application.GetResourceStream(imgUri);
BitmapImage image = new BitmapImage();
image.SetSource(imageResource.Stream);
return image;
}
private void SaveTileImage(WriteableBitmap wbmp, string filename)
{
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
{
if (store.FileExists(filename))
store.DeleteFile(filename);
var stream = store.OpenFile(filename, FileMode.OpenOrCreate);
wbmp.SaveJpeg(stream, wbmp.PixelWidth, wbmp.PixelHeight, 100, 100);
stream.Close();
}
}
private WriteableBitmap CreateTileImageWithCloud(BitmapImage img)
{
Image image = null;
WriteableBitmap wbmp = null;
using (AutoResetEvent are = new AutoResetEvent(false))
{
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
image = new Image { Source = img };
Canvas.SetLeft(image, 0);
Canvas.SetTop(image, 0);
var cloud = new BitmapImage(new Uri("Assets/Images/Other/Cloud_no.png", UriKind.Relative));
var cloudImg = new Image { Source = cloud };
Canvas.SetLeft(cloudImg, 125);
Canvas.SetTop(cloudImg, 10);
var canvas = new Canvas
{
Height = 176,
Width = 176
};
canvas.Children.Add(image);
canvas.Children.Add(cloudImg);
wbmp = new WriteableBitmap(176, 176);
wbmp.Render(canvas, null);
wbmp.Invalidate();
are.Set();
});
are.WaitOne();
}
return wbmp;
}
Edit
I found little pattern in which this is working and in which not. When application is running and I called this twice (in TrackReady and SkipNext) then I very often get cover image with cloud. When I am running just background agent (without running app) I get always black image. And often first UpdateAppTile call is just black image and second it's black image with cloud. That black color is default canvas background so I guess I have problems with delay when loading cover image from url. But I am not sure how in my case use ImageOpened event and if it help.

Answer 1

I think that you should call Measure and Arrange after adding elements to canvas and before rendering canvas (as with other UIElements):
canvas.Measure( new Size( Width, Height ) );
canvas.Arrange( new Rect( 0, 0, Width, Height ) );