WP7 - Using Storyboard defined in Application.Resources

Question

In my Application.Resources I have the following Storyboard defined.

<Application.Resources>
  <!--Storyboard animation for fading out a UI element-->
  <Storyboard x:Key="FadeOutAnimation">
    <DoubleAnimation From="1"
                     To="0"
                     Duration="0:0:0.25"
                     Storyboard.TargetProperty="Opacity"
                     AutoReverse="False" />
  </Storyboard>
</Application.Resources>

In code-behind I'm using this to fade out some TextBlocks when the user taps on them.

// Get the storyboard from application resources
Storyboard sb = (Storyboard)App.Current.Resources["FadeOutAnimation"];
// Setup the animation target for fade out
Storyboard.SetTarget( sb.Children.ElementAt( 0 ) as DoubleAnimation, myTextBlock );
// Set the animation completed handler
sb.Completed += ( s, e1 ) => {
  // Stop the Storyboard
  sb.Stop();
  // Hide the TextBlock
  myTextBlock.Visibility = Visibility.Collapsed;
};
// Start the Storyboard
sb.begin();

The question is, do I need to somehow 'unhook' myTextBlock from being the target of the DoubleAnimation?

If yes, how do I do it?

The reason I'm asking is I'm worried about a reference to that TextBlock hanging around until this Storyboard is used again.

Thanks for your help!

Answer 1

We don't always have to use Xaml in sliverlight if its getting in our way:-

  public static AnimationHelper
  {
       public static void FadeOutAndCollapse(UIElement target)
       {
           DoubleAnimation da = new DoubleAnimation();
           da.From = 1.0;
           da.To = 0.0;
           da.Duration = TimeSpan.FromSeconds(0.25);
           da.AutoReverse = false;

           StoryBoard.SetTargetProperty(da, new PropertyPath("Opacity"));
           StoryBoard.SetTarget(da, target);

           StoryBoard sb = new StoryBoard();
           sb.Children.Add(da);

           EventHandler eh = null;
           eh = (s, args) =>
           {
                target.Visiblity = Visibility.Collapsed;
                sb.Stop();
                sb.Completed -= eh;
           }
           sb.Completed += eh;

           sb.Begin();
       }
}

With this in place you can fade out and collapse any UI element with:-

AnimationHelper.FadeOutAndCollapse(myTextBox);

I'd been inclined to remove the From = 1.0 to make it more general so that elements that have a lower starting opacity don't suddenly flash to full opacity before disappearing.