WPF：防止「已完成」事件在刪除動畫後觸發

Question

如何從WPF元素中刪除正在運行的動畫，以使其Completed事件不會觸發？

提供的解決方案爲here和here刪除動畫的可見效果，但Completed事件在動畫完成時仍會觸發。

下面是一些代碼，演示了我的問題（這是在一個標籤，一個按鈕的窗口背後的代碼，和一個TextBox）：

int _count = 0; 

    private void button1_Click(object sender, RoutedEventArgs e) { 
     myLabel.Content = "Starting animation: " + _count++; 

     // Cancel any already-running animations and return 
     // the label opacity to 1.0. 
     myLabel.BeginAnimation(Label.OpacityProperty, null); 
     myLabel.Opacity = 1.0; 

     // Create a new animation to fade out the label. 
     DoubleAnimation opacityAnim = new DoubleAnimation(1.0, 0.0, TimeSpan.FromSeconds(2), FillBehavior.Stop) { 
      BeginTime = TimeSpan.FromSeconds(3) 
     }; 
     opacityAnim.Completed += (sndr, ev) => { 
      myTextbox.Text += Environment.NewLine + "Completed fired."; 
     }; 

     // Start the countdown/animation. 
     myLabel.BeginAnimation(Label.OpacityProperty, opacityAnim); 
    } 

如何刪除的動畫，使得它不會提高其Completed事件？

Answer 1

從已完成的情況下取消...這也意味着你必須從lambda來顯式方法重寫完成事件處理程序：

DoubleAnimation _opacityAnim; // Created somewhere else. 

    private void button1_Click(object sender, RoutedEventArgs e) 
    { 
    myLabel.Content = "Starting animation: " + _count++; 

    // Cancel any already-running animations and return 
    // the label opacity to 1.0. 
    _opacityAnim.Completed -= AnimationCompleted; 

    myLabel.BeginAnimation(Label.OpacityProperty, null); 
    myLabel.Opacity = 1.0; 

    // Create a new animation to fade out the label. 
    opacityAnim.Completed += AnimationCompleted; 

    // Start the countdown/animation. 
    myLabel.BeginAnimation(Label.OpacityProperty, opacityAnim); 
} 

private void AnimationCompleted(object sender, EventArgs e) 
{ 
     myTextbox.Text += Environment.NewLine + "Completed fired."; 
}