如何：在使用演示图板对属性进行动画处理后设置该属性

项目
05/04/2023

在某些情况下，在对属性进行动画处理后，看起来可能无法更改该属性的值。

对 SolidColorBrush 的颜色进行动画处理

在以下示例中，Storyboard 用于对 SolidColorBrush 的颜色进行动画处理。单击按钮时将触发情节提要。处理 Completed 事件以便在 ColorAnimation 完成时通知程序。

<Button
  Content="Animate and Then Set Example 1">
  <Button.Background>
    <SolidColorBrush x:Name="Button1BackgroundBrush"
      Color="Red" />
  </Button.Background>
  <Button.Triggers>
    <EventTrigger RoutedEvent="Button.Click">
      <BeginStoryboard>
        <Storyboard>
          <ColorAnimation
            Storyboard.TargetName="Button1BackgroundBrush"
            Storyboard.TargetProperty="Color"
            From="Red" To="Yellow" Duration="0:0:5"
            FillBehavior="HoldEnd"
            Completed="setButton1BackgroundBrushColor" />
        </Storyboard>
      </BeginStoryboard>
    </EventTrigger>
  </Button.Triggers>
</Button>

更改画笔颜色

ColorAnimation 完成后，程序会尝试将画笔的颜色更改为蓝色。

private void setButton1BackgroundBrushColor(object sender, EventArgs e)
{

    // Does not appear to have any effect:
    // the brush remains yellow.
    Button1BackgroundBrush.Color = Colors.Blue;
}

Private Sub setButton1BackgroundBrushColor(ByVal sender As Object, ByVal e As EventArgs)

    ' Does not appear to have any effect:
    ' the brush remains yellow.
    Button1BackgroundBrush.Color = Colors.Blue
End Sub

前面的代码似乎未执行任何操作：画笔保持为黄色，这是对画笔进行动画处理的 ColorAnimation 提供的值。基础属性值（基值）实际上已更改为蓝色。但是，有效值或当前值仍为黄色，因为 ColorAnimation 仍在重写基值。如果要让基值再次成为有效值，则必须停止动画对属性的影响。使用情节提要动画可以通过三种方式实现此操作：

将动画的 FillBehavior 属性设置为 Stop
删除整个情节提要。
从单个属性中删除动画。

将动画的 FillBehavior 属性设置为 Stop

通过将 FillBehavior 设置为 Stop，可以告诉动画在其活动期结束时停止影响其目标属性。

<Button
  Content="Animate and Then Set Example 2">
  <Button.Background>
    <SolidColorBrush x:Name="Button2BackgroundBrush"
      Color="Red" />
  </Button.Background>
  <Button.Triggers>
    <EventTrigger RoutedEvent="Button.Click">
      <BeginStoryboard>
        <Storyboard>
          <ColorAnimation
            Storyboard.TargetName="Button2BackgroundBrush"
            Storyboard.TargetProperty="Color"
            From="Red" To="Yellow" Duration="0:0:5"
            FillBehavior="Stop"
            Completed="setButton2BackgroundBrushColor" />
        </Storyboard>
      </BeginStoryboard>
    </EventTrigger>
  </Button.Triggers>
</Button>

private void setButton2BackgroundBrushColor(object sender, EventArgs e)
{

    // This appears to work:
    // the brush changes to blue.
    Button2BackgroundBrush.Color = Colors.Blue;
}

Private Sub setButton2BackgroundBrushColor(ByVal sender As Object, ByVal e As EventArgs)

    ' This appears to work:
    ' the brush changes to blue.
    Button2BackgroundBrush.Color = Colors.Blue
End Sub

删除整个情节提要

通过使用 RemoveStoryboard 触发器或 Storyboard.Remove 方法，可以告诉情节提要动画停止影响其目标属性。此方法与设置 FillBehavior 属性的区别在于，可以随时删除情节提要，而 FillBehavior 属性仅在动画活动期结束时才有效。

<Button
  Name="Button3"
  Content="Animate and Then Set Example 3">
  <Button.Background>
    <SolidColorBrush x:Name="Button3BackgroundBrush"
      Color="Red" />
  </Button.Background>
  <Button.Triggers>
    <EventTrigger RoutedEvent="Button.Click">
      <BeginStoryboard Name="MyBeginStoryboard">
        <Storyboard x:Name="MyStoryboard">
          <ColorAnimation
            Storyboard.TargetName="Button3BackgroundBrush"
            Storyboard.TargetProperty="Color"
            From="Red" To="Yellow" Duration="0:0:5"
            FillBehavior="HoldEnd"
            Completed="setButton3BackgroundBrushColor" />
        </Storyboard>
      </BeginStoryboard>
    </EventTrigger>
  </Button.Triggers>
</Button>

private void setButton3BackgroundBrushColor(object sender, EventArgs e)
{

     // This appears to work:
    // the brush changes to blue.
    MyStoryboard.Remove(Button3);
    Button3BackgroundBrush.Color = Colors.Blue;
}

Private Sub setButton3BackgroundBrushColor(ByVal sender As Object, ByVal e As EventArgs)

     ' This appears to work:
    ' the brush changes to blue.
    MyStoryboard.Remove(Button3)
    Button3BackgroundBrush.Color = Colors.Blue
End Sub

从单个属性中删除动画

另一种阻止动画影响属性的技术是使用正在进行动画处理的对象的 BeginAnimation(DependencyProperty, AnimationTimeline) 方法。将正在进行动画处理的属性指定为第一个参数，并将 null 指定为第二个参数。

<Button
  Name="Button4"
  Content="Animate and Then Set Example 4">
  <Button.Background>
    <SolidColorBrush x:Name="Button4BackgroundBrush"
      Color="Red" />
  </Button.Background>
  <Button.Triggers>
    <EventTrigger RoutedEvent="Button.Click">
      <BeginStoryboard>
        <Storyboard>
          <ColorAnimation
            Storyboard.TargetName="Button4BackgroundBrush"
            Storyboard.TargetProperty="Color"
            From="Red" To="Yellow" Duration="0:0:5"
            FillBehavior="HoldEnd"
            Completed="setButton4BackgroundBrushColor" />
        </Storyboard>
      </BeginStoryboard>
    </EventTrigger>
  </Button.Triggers>
</Button>

private void setButton4BackgroundBrushColor(object sender, EventArgs e)
{

     // This appears to work:
    // the brush changes to blue.
    Button4BackgroundBrush.BeginAnimation(SolidColorBrush.ColorProperty, null);
    Button4BackgroundBrush.Color = Colors.Blue;
}

Private Sub setButton4BackgroundBrushColor(ByVal sender As Object, ByVal e As EventArgs)

     ' This appears to work:
    ' the brush changes to blue.
    Button4BackgroundBrush.BeginAnimation(SolidColorBrush.ColorProperty, Nothing)
    Button4BackgroundBrush.Color = Colors.Blue
End Sub

此技术也适用于非情节提要动画。

通过