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如何:使用腳本建立屬性的動畫後進行設定

在某些情況下,您可能會在產生動畫效果之後,無法變更屬性的值。

以動畫顯示 SolidColorBrush 的色彩

在下列範例中,Storyboard 是用來以動畫顯示 SolidColorBrush 的色彩。 按一下按鈕時,就會觸發分鏡腳本。 系統會處理 Completed 事件,以便程式在 ColorAnimation 完成時收到通知。

<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>

變更筆刷色彩

ColorAnimation 完成之後,程式會嘗試將筆刷的色彩變更為藍色。

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

先前的程式碼似乎不會執行任何動作:筆刷會維持黃色,這是以動畫顯示筆刷的 ColorAnimation 所提供的值。 基礎屬性值 (基本值) 實際上會變更為藍色。 不過,有效或目前的值會維持黃色,因為 ColorAnimation 仍在覆寫基本值。 如果您想要讓基本值再次成為有效值,則必須防止動畫影響屬性。 有三種方式可以透過分鏡腳本動畫來執行此動作:

  • 將動畫的 FillBehavior 屬性設定為 Stop

  • 移除整個分鏡腳本。

  • 從個別屬性移除動畫。

將動畫的 FillBehavior 屬性設定為 Stop

藉由將 FillBehavior 設定 Stop 為,您可以告訴動畫在到達作用期間結束之後停止影響其目標屬性。

<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

移除整個分鏡腳本

藉由使用 RemoveStoryboard 觸發程序或 Storyboard.Remove 方法,您可以告訴分鏡腳本動畫停止影響其目標屬性。 此方法與設定 FillBehavior 屬性之間的差異在於,您可以隨時移除分鏡腳本,而 FillBehavior 屬性只有在動畫到達作用期間結束時才會有效果。

<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

從個別屬性移除動畫

防止動畫影響屬性的另一個技巧是使用正在產生動畫之物件的 BeginAnimation(DependencyProperty, AnimationTimeline) 方法。 指定要顯示動畫的屬性做為第一個參數,並指定 null 作為第二個。

<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

這項技術也適用於非分鏡腳本動畫。

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