只需停止異步方法

Question

我有這種方法播放聲音，當用戶點擊屏幕時，我想讓它在用戶再次點擊屏幕時停止播放。但問題是「DoSomething（）」方法並沒有停止，它一直持續到它完成。

bool keepdoing = true; 

private async void ScreenTap(object sender, System.Windows.Input.GestureEventArgs e) 
    { 
     keepdoing = !keepdoing; 
     if (!playing) { DoSomething(); } 
    } 

private async void DoSomething() 
    { 
     playing = true; 
     for (int i = 0; keepdoing ; count++) 
     { 
      await doingsomething(text); 
     } 
     playing = false; 
    } 

任何幫助將不勝感激。
謝謝:)

Answer 1

這是CancellationToken的用途。

CancellationTokenSource cts; 

private async void ScreenTap(object sender, System.Windows.Input.GestureEventArgs e) 
{ 
    if (cts == null) 
    { 
    cts = new CancellationTokenSource(); 
    try 
    { 
     await DoSomethingAsync(cts.Token); 
    } 
    catch (OperationCanceledException) 
    { 
    } 
    finally 
    { 
     cts = null; 
    } 
    } 
    else 
    { 
    cts.Cancel(); 
    cts = null; 
    } 
} 

private async Task DoSomethingAsync(CancellationToken token) 
{ 
    playing = true; 
    for (int i = 0; ; count++) 
    { 
    token.ThrowIfCancellationRequested(); 
    await doingsomethingAsync(text, token); 
    } 
    playing = false; 
}