How to get ObjectAnimationUsingKeyFrames to work programmatically

How to get ObjectAnimationUsingKeyFrames to work programmatically

• cwlaualex

  Ok sounds good... it would be nice if Storyboard had an OnCompleted method in addition to the existing Completed event. I'd like to create a class that inherits Storyboard and perform my cleanup in OnCompleted. I can use the Completed event for now though.
  
  

• Raoul_BennetH

  One thing you can do is to set the underlying property to the value you wish to persist after the storyboard to the final value. So, here, you could set element.Visibility to Visbility.Collapsed and then create a Keyframe at 0 equal to the old value of the Visibility value. Since both starting the animation and the visibility change would happen "simultaneously", nothing would appear to change, but when the storyboard stops (or is removed), the local value would take effect again, which would be Collapsed.

  -Adam Smith [MS]

  
  
  

• Vaassu

  Ok, I figured out my own answer after playing around some more. FillBehavior.Stop seems to make the value reset to its pre-animation value. And since I had my keyframe at the end of the animation, it made its change and changed it back right away.

  So if I take that out I run into a new problem. FillBehavior is switched to HoldEnd (the default value). If that is set I do get the proper behavior where the element hides after a second. But the problem is that I can no longer set the Visibility property of the element directly in code. Other animations can modify it though. So it seems like the storyboard is still attached and is in some animating state. Do I need to remove the storyboard or animation somehow when it's done and what's the best way to do this

  
  
  

• Macinkross

  Right - Stop behavior, or remove the storboard entirely. The standard pattern is to register a callback with the Completed event which removes the storyboard, thus "freeing" the local values from animation override.

  -Adam Smith [MS]

  
  
  

• sohaibi

  Thanks, that seems to work. And I assume your recommendation would work only with the Stop fill behavior, correct

  Out of curiosity, since HoldEnd fill behavior seems to be forcing the end value to stick with the control and will not allow the value to be changed by setting the property directly, how would I remove that "hold" or "freeze" if I did want to be able to switch the property value via code again

  
  
  

• SimonJohns

  Adam Smith MS wrote:

  Right - Stop behavior, or remove the storboard entirely. The standard pattern is to register a callback with the Completed event which removes the storyboard, thus "freeing" the local values from animation override.

  Arrgg... still can't get it to work with HoldEnd functionality. Please try this simple test. I have a Button on a window and when clicked, it will start a storyboard of a second long. Halfway through it hides itself. Then at the end of the storyboard, it should make itself visible again via code. I'm attaching to the Completed event but the button still is being animated as I can see from my console printout message.

  Here is the code:

  ---
  private void button_Click(object sender, EventArgs e) {
  Console.WriteLine("BEFORE: " + button.Visibility + " : " + button.HasAnimatedProperties);

  // Create the storyboard
  Storyboard storyboard = new Storyboard();
  storyboard.Completed += new EventHandler(storyboard_Completed);

  // Add keyframe to turn off from button visibility
  ObjectAnimationUsingKeyFrames kf = new ObjectAnimationUsingKeyFrames();
  Storyboard.SetTargetProperty(kf, new PropertyPath(FrameworkElement.VisibilityProperty));
  kf.Duration = TimeSpan.FromSeconds(1);
  kf.KeyFrames.Add(new DiscreteObjectKeyFrame(Visibility.Collapsed, KeyTime.FromPercent(.5)));
  storyboard.Children.Add(kf);

  // Start the storyboard
  storyboard.Begin(button);
  }

  void storyboard_Completed(object sender, EventArgs e) {
  button.Visibility = Visibility.Visible;
  Console.WriteLine("COMPLETE: " + button.Visibility + " : " + button.HasAnimatedProperties);
  }
  ---

  And when I run the window and click the button I get these messages:

  BEFORE: Visible : False
  COMPLETE: Collapsed : True

  Based on what you said I woudl expect the messages to be these instead:

  BEFORE: Visible : False
  COMPLETE: Visible : False

  Any ideas

  
  
  

• Itzik Katzav

  Ah, sorry - registering with the Completed event isn't sufficient. What I meant to suggest was that you consider registering a callback with the Completed event, and to then Remove the storyboard in the callback.

  For example (from yours above):

  // Create the storyboard
  Storyboard storyboard = new Storyboard();
  storyboard.Completed += delegate(object sender, EventArgs e)
  {
  button.Visibility = Visibility.Visible;
  storyboard.Remove(button);
  };

  -Adam Smith [MS]

  
  
  
• How to get ObjectAnimationUsingKeyFrames to work programmatically