UWP System.*Exception

Question

为了测试它，我使用combobox_selectionChanged事件来激活此功能，当selectedItem = 0显示世界标题时，selectedItem = 1显示体育标题，selectedItem = 2将可见性更改为折叠。当您选择item0或更改ITEM1它可以工作，但一旦我改变ITEM2，它让我system.*Exception

这里是我的代码`

CancellationTokenSource cts = null; 
    public async void NewsRepeat() 
    {   
     cts?.Cancel(); 
     try 
     { 
      var localCts = cts = new CancellationTokenSource();       
      localCts.Token.ThrowIfCancellationRequested(); 
      if (newsTpye.SelectedIndex == 0) 
      { 
       NewsPanel.Visibility = Visibility.Visible; 
       RootObject2 myNews = await NewsProxy.GetNews(); 
       newsChannel.Text = "World Headlines"; 
       for (k = 0; k <= 8; k++) 
       { 
        if (myNews.articles[k].title != null) 
         showTitle.Text = myNews.articles[k].title; 
        else 
         showTitle.Text = ""; 
        if (myNews.articles[k].urlToImage != null) 
         newsImage.Source = new BitmapImage(new Uri(myNews.articles[k].urlToImage, UriKind.Absolute)); 
        else 
         newsImage.Source = new BitmapImage(new Uri("ms-appx:///Assets/image/NoPic.jpg", UriKind.RelativeOrAbsolute)); 
        if (myNews.articles[k].publishedAt != null) 
         showTime.Text = myNews.articles[k].publishedAt; 
        else 
         showTime.Text = ""; 
        showDescription.Text = "(" + myNews.source + "): " + myNews.articles[k].description; 
        await Task.Delay(5000); 
        localCts.Token.ThrowIfCancellationRequested(); 
       } 

      } 
      else if (newsTpye.SelectedIndex == 1) 
      { 
       NewsPanel.Visibility = Visibility.Visible; 
       RootObject3 mySportNews = await sportsNewsProxy.GetSportNews(); 
       newsChannel.Text = "Sports Headlines"; 

       for (k = 0; k <= 8; k++) 
       { 
        if (mySportNews.articles[k].title != null) 
         showTitle.Text = mySportNews.articles[k].title; 
        else 
         showTitle.Text = ""; 

        if (mySportNews.articles[k].urlToImage != null) 
         newsImage.Source = new BitmapImage(new Uri(mySportNews.articles[k].urlToImage, UriKind.Absolute)); 
        else 
         newsImage.Source = new BitmapImage(new Uri("ms-appx:///Assets/image/NoPic.jpg", UriKind.RelativeOrAbsolute)); 

        if (mySportNews.articles[k].publishedAt != null) 
         showTime.Text = mySportNews.articles[k].publishedAt; 
        else 
         showTime.Text = ""; 
        showDescription.Text = "(" + mySportNews.source + "): " + mySportNews.articles[k].description; 
        await Task.Delay(5000); 
        localCts.Token.ThrowIfCancellationRequested(); 
       } 
      } 
      else if (newsTpye.SelectedIndex == 2) 
      { 
       NewsPanel.Visibility = Visibility.Collapsed; 
      } 
      NewsRepeat(); 
     } 
     catch (OperationCanceledException) 
     { 
      // Swallow this exception only - this is probably 
      // the one we've thrown ourselves 
     } 
    } 

    private void newsType_SelectionChanged(object sender, SelectionChangedEventArgs e) 
    { 

     NewsRepeat(); 
    }` 

Answer 1

每次你调用一个方法，你会增加堆栈的使用。当SelectedIndex == 2，你的方法会一遍又一遍地调用自己，导致堆栈溢出。

你能教导如何退出吗？

使用return声明。

请注意，您应该使用async Task。 async void主要针对事件处理程序。