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Timing Behaviors Overview

Learn about the Timing Behaviors Overview.

03/30/2017

devdivchpfy22

timing behaviors [WPF]

behaviors [WPF], timing

5b714d46-bd46-48b8-b467-b4be89ba3091

Timing Behaviors Overview

This topic describes the timing behaviors of animations and other xref:System.Windows.Media.Animation.Timeline objects.

Prerequisites

To understand this topic, you should be familiar with basic animation features. For more information, see the Animation Overview.

Timeline Types

A xref:System.Windows.Media.Animation.Timeline represents a segment of time. It provides properties that enable you to specify the length of that segment, when it should start, how many times it will repeat, how fast time progresses in that segment, and more.

Classes that inherit from the timeline class provide additional functionality, such as animation and media playback. [!INCLUDETLA2#tla_winclient] provides the following xref:System.Windows.Media.Animation.Timeline types.

Timeline type	Description
xref:System.Windows.Media.Animation.AnimationTimeline	Abstract base class for xref:System.Windows.Media.Animation.Timeline objects that generate output values for animating properties.
xref:System.Windows.Media.MediaTimeline	Generates output from a media file.
xref:System.Windows.Media.Animation.ParallelTimeline	A type of xref:System.Windows.Media.Animation.TimelineGroup that groups and controls child xref:System.Windows.Media.Animation.Timeline objects.
xref:System.Windows.Media.Animation.Storyboard	A type of xref:System.Windows.Media.Animation.ParallelTimeline that provides targeting information for the Timeline objects it contains.
xref:System.Windows.Media.Animation.Timeline	Abstract base class that defines timing behaviors.
xref:System.Windows.Media.Animation.TimelineGroup	Abstract class for xref:System.Windows.Media.Animation.Timeline objects that can contain other xref:System.Windows.Media.Animation.Timeline objects.

Properties that Control the Length of a Timeline

A xref:System.Windows.Media.Animation.Timeline represents a segment of time, and the length of a timeline can be described in different ways. The following table defines several terms for describing the length of a timeline.

Term	Description	Properties
Simple duration	The length of time a timeline takes to make a single forward iteration.	xref:System.Windows.Media.Animation.Timeline.Duration%2A
One repetition	The length of time it takes for a timeline to play forward once and, if the xref:System.Windows.Media.Animation.Timeline.AutoReverse%2A property is true, play backwards once.	xref:System.Windows.Media.Animation.Timeline.Duration%2A, xref:System.Windows.Media.Animation.Timeline.AutoReverse%2A
Active period	The length of time it takes for a timeline to complete all the repetitions specified by its xref:System.Windows.Media.Animation.RepeatBehavior property.	xref:System.Windows.Media.Animation.Timeline.Duration%2A, xref:System.Windows.Media.Animation.Timeline.AutoReverse%2A, xref:System.Windows.Media.Animation.RepeatBehavior

The Duration Property

As previously mentioned, a timeline represents a segment of time. The length of that segment is determined by the timeline's xref:System.Windows.Media.Animation.Timeline.Duration%2A. When a timeline reaches the end of its duration, it stops playing. If the timeline has child timelines, they stop playing as well. In the case of an animation, the xref:System.Windows.Media.Animation.Timeline.Duration%2A specifies how long the animation takes to transition from its starting value to its ending value. A timeline's duration is sometimes called its simple duration, to distinguish between the duration of a single iteration and the total length of time the animation plays including repetitions. You can specify a duration using a finite time value or the special values xref:System.Windows.Duration.Automatic%2A or xref:System.Windows.Duration.Forever%2A. An animation's duration should resolve to a xref:System.Windows.Duration.TimeSpan%2A value, so it can transition between values.

The following example shows a xref:System.Windows.Media.Animation.DoubleAnimation with a xref:System.Windows.Media.Animation.Timeline.Duration%2A of five seconds.

[!code-xamlanimation_ovws_snippet#AnimationWith5SecondDurationInline]

Container timelines, such as xref:System.Windows.Media.Animation.Storyboard and xref:System.Windows.Media.Animation.ParallelTimeline, have a default duration of xref:System.Windows.Duration.Automatic%2A, which means they automatically end when their last child stops playing. The following example shows a xref:System.Windows.Media.Animation.Storyboard whose xref:System.Windows.Media.Animation.Timeline.Duration%2A resolves to five seconds, the length of time it takes all its child xref:System.Windows.Media.Animation.DoubleAnimation objects to complete.

[!code-xamlanimation_ovws_snippet#ContainerTimelineExampleInline]

By setting the xref:System.Windows.Media.Animation.Timeline.Duration%2A of a container timeline to a xref:System.Windows.Duration.TimeSpan%2A value, you can force to play longer or shorter than its child xref:System.Windows.Media.Animation.Timeline objects would play. If you set the xref:System.Windows.Media.Animation.Timeline.Duration%2A to a value that's smaller than the length of the container timeline's child xref:System.Windows.Media.Animation.Timeline objects, the child xref:System.Windows.Media.Animation.Timeline objects stop playing when the container timeline does. The following example sets the xref:System.Windows.Media.Animation.Timeline.Duration%2A of the xref:System.Windows.Media.Animation.Storyboard from the preceding examples to three seconds. As a result, the first xref:System.Windows.Media.Animation.DoubleAnimation stops progressing after three seconds, when it has animated the target rectangle's width to 60.

[!code-xamlanimation_ovws_snippet#ContainerTimelineWithShorterDurationExampleInline]

The RepeatBehavior Property

The xref:System.Windows.Media.Animation.Timeline.RepeatBehavior%2A property of a xref:System.Windows.Media.Animation.Timeline controls how many times it repeats its simple duration. Using the xref:System.Windows.Media.Animation.Timeline.RepeatBehavior%2A property, you can specify how many times the timeline plays (an iteration xref:System.Windows.Media.Animation.RepeatBehavior.Count%2A) or the total length of time it should play (a repeat xref:System.Windows.Media.Animation.RepeatBehavior.Duration%2A). In either case, the animation goes through as many beginning-to-end runs as necessary to fill the requested count or duration. By default, timelines have an iteration count of 1.0, which means they play once and do not repeat at all.

The following example uses the xref:System.Windows.Media.Animation.Timeline.RepeatBehavior%2A property to make a xref:System.Windows.Media.Animation.DoubleAnimation play for twice its simple duration by specifying an iteration count.

[!code-xamlanimation_ovws_snippet#TBRepeatBehavior2xExampleInline]

The next example uses the xref:System.Windows.Media.Animation.Timeline.RepeatBehavior%2A property to make the xref:System.Windows.Media.Animation.DoubleAnimation play for half its simple duration.

[!code-xamlanimation_ovws_snippet#TBRepeatBehavior05xExampleInline]

If you set the xref:System.Windows.Media.Animation.Timeline.RepeatBehavior%2A property of a xref:System.Windows.Media.Animation.Timeline to xref:System.Windows.Media.Animation.RepeatBehavior.Forever%2A, the xref:System.Windows.Media.Animation.Timeline repeats until stopped interactively or by the timing system. The following example uses the xref:System.Windows.Media.Animation.Timeline.RepeatBehavior%2A property to make the xref:System.Windows.Media.Animation.DoubleAnimation play indefinitely.

[!code-xamlanimation_ovws_snippet#TBRepeatBehaviorForeverExampleInline]

For an additional example, see Repeat an Animation.

The AutoReverse Property

The xref:System.Windows.Media.Animation.Timeline.AutoReverse%2A property specifies whether a xref:System.Windows.Media.Animation.Timeline will play backwards at the end of each forward iteration. The following example sets to the xref:System.Windows.Media.Animation.Timeline.AutoReverse%2A property of a xref:System.Windows.Media.Animation.DoubleAnimation to true; as a result, it animates from zero to 100, and then from 100 to zero. It plays for a total of 10 seconds.

[!code-xamlanimation_ovws_snippet#TBAutoReverseExampleInline]

[!code-xamlanimation_ovws_snippet#TBAutoReverseRepeatExampleInline]

If a container timeline has child xref:System.Windows.Media.Animation.Timeline objects, they reverse when the container timeline does. For additional examples, see Specify Whether a Timeline Automatically Reverses.

The BeginTime Property

The xref:System.Windows.Media.Animation.Timeline.BeginTime%2A property enables you to specify when a timeline starts. A timeline's begin time is relative to its parent timeline. A begin time of zero seconds means the timeline starts as soon as it parent starts; any other value creates an offset between when the parent timeline starts playing and when the child timeline plays. For example, a begin time of two seconds means the timeline starts playing when its parent has reached a time of two seconds. By default, all timelines have a begin time of zero seconds. You may also set a timeline's begin time to null, which prevents the timeline from starting. In [!INCLUDETLA2#tla_winclient], you specify null using the x:Null Markup Extension.

Note that the begin time is not applied each time a timeline repeats because of its xref:System.Windows.Media.Animation.Timeline.RepeatBehavior%2A setting. If you were to create an animation with a xref:System.Windows.Media.Animation.Timeline.BeginTime%2A of 10 seconds and a xref:System.Windows.Media.Animation.RepeatBehavior of xref:System.Windows.Media.Animation.RepeatBehavior.Forever%2A, there would be a 10-second delay before the animation played for the first time, but not for each successive repetition. However, if the animation's parent timeline were to restart or repeat, the 10-second delay would occur.