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title, ms.date, dev_langs, helpviewer_keywords, ms.assetid
| title | ms.date | dev_langs | helpviewer_keywords | ms.assetid | ||||
|---|---|---|---|---|---|---|---|---|
| How to: Receive Notification When a Clock's State Changes | 03/30/2017 |
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ecb10fc9-d0c2-45c3-b0a1-7b11baa733da |
How to: Receive Notification When a Clock's State Changes
A clock's xref:System.Windows.Media.Animation.Clock.CurrentStateInvalidated event occurs when its xref:System.Windows.Media.Animation.Clock.CurrentState%2A becomes invalid, such as when the clock starts or stops. You can register for this event with directly using a xref:System.Windows.Media.Animation.Clock, or you can register using a xref:System.Windows.Media.Animation.Timeline.
In the following example, a xref:System.Windows.Media.Animation.Storyboard and two xref:System.Windows.Media.Animation.DoubleAnimation objects are used to animate the width of two rectangles. The xref:System.Windows.Media.Animation.Timeline.CurrentStateInvalidated event is used to listen for clock state changes.
Example
[!code-xamltimingbehaviors_snip#_graphicsmm_StateExampleMarkupWholePage]
[!code-csharptimingbehaviors_snip#_graphicsmm_StateEventHandlers] [!code-vbtimingbehaviors_snip#_graphicsmm_StateEventHandlers]
The following illustration shows the different states the animations enter as the parent timeline (Storyboard) progresses.
The following table shows the times at which Animation1's xref:System.Windows.Media.Animation.Timeline.CurrentStateInvalidated event fires:
| Time (Seconds) | 1 | 10 | 19 | 21 | 30 | 39 |
| State | Active | Active | Stopped | Active | Active | Stopped |
The following table shows the times at which Animation2's xref:System.Windows.Media.Animation.Timeline.CurrentStateInvalidated event fires:
| Time (Seconds) | 1 | 9 | 11 | 19 | 21 | 29 | 31 | 39 |
| State | Active | Filling | Active | Stopped | Active | Filling | Active | Stopped |
Notice that Animation1's xref:System.Windows.Media.Animation.Timeline.CurrentStateInvalidated event fires at 10 seconds, even though its state remains xref:System.Windows.Media.Animation.ClockState.Active. That's because its state changed at 10 seconds, but it changed from xref:System.Windows.Media.Animation.ClockState.Active to xref:System.Windows.Media.Animation.ClockState.Filling and then back to xref:System.Windows.Media.Animation.ClockState.Active in the same tick.