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How to: Animate Size Changes by Using Key Frames

  • Artikkeli

This example shows how to animate size changes by using key frames.

Example

The following example uses the SizeAnimationUsingKeyFrames class to animate the Size property of an ArcSegment. This animation uses three key frames in the following manner:

  1. During the first half second of the animation, uses an instance of the LinearSizeKeyFrame class to gradually increase the size of the arc. Linear key frames like LinearSizeKeyFrame create a smooth linear transition between values.

  2. At the end of the next half second, uses an instance of the DiscreteSizeKeyFrame class to suddenly increase the size of the arc. Discrete key frames like DiscreteSizeKeyFrame create sudden jumps between values, that is, the size changes occur suddenly and are not subtle.

  3. Over the final two seconds, uses an instance of the SplineSizeKeyFrame class to increase the size of the arc. Spline key frames like SplineSizeKeyFrame create a variable transition between values according to the values of the KeySpline property. In this example, the size of the arc increases slowly at first and then increases exponentially toward the end of the time segment.

<!-- This example shows how to use the SizeAnimationUsingKeyFrames to animate the
size of an ArcSegment. -->
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" >

    <Canvas HorizontalAlignment="Left" Margin="0" >

      <!-- Create an arc on the screen that animates its size when it loads. -->
      <Path Stroke="Black" StrokeThickness="2" >
        <Path.Data>
          <PathGeometry>
            <PathGeometry.Figures>
              <PathFigureCollection>
                <PathFigure StartPoint="100,200">
                  <PathFigure.Segments>
                    <PathSegmentCollection>
                      <ArcSegment x:Name="myArcSegment" Size="90,80" 
                      SweepDirection="Clockwise"  Point="500,200" />
                    </PathSegmentCollection>
                  </PathFigure.Segments>
                </PathFigure>
              </PathFigureCollection>
            </PathGeometry.Figures>
          </PathGeometry>
        </Path.Data>
        <Path.Triggers>
          <EventTrigger RoutedEvent="Path.Loaded">
            <BeginStoryboard Name="myBeginStoryBoard">
              <Storyboard>
                
                <!-- Animating the Size property uses 3 KeyFrames. -->
                <SizeAnimationUsingKeyFrames
                Storyboard.TargetName="myArcSegment"
                Storyboard.TargetProperty="Size" >
                  <SizeAnimationUsingKeyFrames.KeyFrames>
                    <!-- Using a LinearSizeKeyFrame, the size of the arc increases
                         gradually over the first half second of the animation. -->
                    <LinearSizeKeyFrame KeyTime="0:0:0.5" Value="120,120" />

                    <!-- Using a DiscreteSizeKeyFrame, the size increases suddenly
                    after the first second of the animation. -->
                    <DiscreteSizeKeyFrame KeyTime="0:0:1" Value="150,150" />

                    <!-- Using a SplineSizeKeyFrame, the Size increases slowly at first 
                         and then speeds up exponentially. This KeyFrame takes 2 seconds. -->
                    <SplineSizeKeyFrame KeySpline="0.6,0.0 0.9,0.00" KeyTime="0:0:3" Value="300,300" />

                  </SizeAnimationUsingKeyFrames.KeyFrames>
                </SizeAnimationUsingKeyFrames>

              </Storyboard>
            </BeginStoryboard>
          </EventTrigger>
        </Path.Triggers>
      </Path>
    </Canvas>

</Page>

For the complete sample, see KeyFrame Animation Sample.

See also