LongListSelector SelectedItem为Null(LongListSelector SelectedItem is Null)

我正在玩一个音乐播放器应用程序，并将播放列表存储在列表中。这显示在LongListSelector中，其中包含带有图像和两个文本块的StackPanel：

当用户点击图像时，我想从列表中删除所选歌曲。我使用以下代码：

private void removeSong_Tap(object sender, System.Windows.Input.GestureEventArgs e) { int selectedIndex = playlistList.ItemsSource.IndexOf(playlistList.SelectedItem as ItemViewModel); if (selectedIndex == Data.currentSongNo) { if (Data.currentSongNo == Data.playList.Count - 1) //last song in the playlist { MediaPlayer.Stop(); } else { playNextSong(); } removeSongFromPlaylist(selectedIndex); } }

但每次单击图像时，SelectedItem都会显示为null，表示selectedIndex设置为-1

我也试过用：

int selectedIndex = App.ViewModel.Items.IndexOf(playlistList.SelectedItem as ItemViewModel);

但这有相同的结果。

我有什么想法我做错了吗？

I am playing around with a music player app and have the playlist stored in a List. This is displayed in a LongListSelector containing a StackPanel with an image and two text blocks:

When the user clicks on the image, I want to remove the selected song from the list. I am using the following code:

private void removeSong_Tap(object sender, System.Windows.Input.GestureEventArgs e) { int selectedIndex = playlistList.ItemsSource.IndexOf(playlistList.SelectedItem as ItemViewModel); if (selectedIndex == Data.currentSongNo) { if (Data.currentSongNo == Data.playList.Count - 1) //last song in the playlist { MediaPlayer.Stop(); } else { playNextSong(); } removeSongFromPlaylist(selectedIndex); } }

But every time I click on the image, the SelectedItem comes up as null, meaning the selectedIndex is set to -1

I've also tried using:

int selectedIndex = App.ViewModel.Items.IndexOf(playlistList.SelectedItem as ItemViewModel);

But this has the same results.

Any ideas what I'm doing wrong?

最满意答案

我确定有几种方法可以做到这一点。我实现这一点的一个简单方法是使用在SelectionChanged事件开始时检查的标志。

tap事件将在树中的selection_changed事件之前触发，因此我设置了一个Tap事件，如下所示：

private void ItemClose_Tap(object sender, System.Windows.Input.GestureEventArgs e) { isItemCloseTapped = true; }

然后，当Selection Changed事件触发时，我实现如下：

private void MusicListSelectChange(object sender, SelectionChangedEventArgs e) { Model.MusicItem item = ((LongListSelector)sender).SelectedItem as Model.MusicItem; if (item == null) return; if (isItemCloseTapped ) { CloseInList(item); isItemCloseTapped = false; } //... //((LongListSelector)sender).SelectedItem = null; )

同样，这是一种方法，但它在我的结束时运作良好。

There are a few ways to do this I'm sure. One simple way I've implemented this is to use a flag that's checked at the start of the SelectionChanged event.

The tap event will fire before the selection_changed event in the tree, so I've set up a Tap event like this:

private void ItemClose_Tap(object sender, System.Windows.Input.GestureEventArgs e) { isItemCloseTapped = true; }

Then, as the Selection Changed event fires, I've implemented as follows:

private void MusicListSelectChange(object sender, SelectionChangedEventArgs e) { Model.MusicItem item = ((LongListSelector)sender).SelectedItem as Model.MusicItem; if (item == null) return; if (isItemCloseTapped ) { CloseInList(item); isItemCloseTapped = false; } //... //((LongListSelector)sender).SelectedItem = null; )

Again, this is one way to do it, but it's worked well on my end.

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