MediaPlaybackList.Items.IndexOf（_currentItem）无效!! [英] MediaPlaybackList.Items.IndexOf(_currentItem) is not working !!

问题描述

我正在开发一个音乐播放器。我需要从MediaPlaybackList获取特定项的索引。但是，MediaPlaybackList.Items.IndexOf（_currentItem）始终返回-1。为什么？我需要帮助。 

 MediaPlaybackItem _currentMediaPlaybackItem = new MediaPlaybackItem（MediaSource.CreateFromStorageFile（song.SongFile））; 
 MediaPlaybackList playbacklist = new MediaPlaybackList（）; 
 if（MusicPlayedFrom ==" MyMusicPage"）
 {
 CurrentlyPlayingSong = song; 
 foreach（歌曲中的var项目）
 {
 MediaPlaybackItem playbackItem = new MediaPlaybackItem（MediaSource.CreateFromStorageFile（item.SongFile））; 
 playbacklist.Items.Add（playbackItem）; 
} 
} 
 MediaPlayer.Source = playbacklist; 
 var count = playbacklist.Items.Count; 
 var index = playbacklist.Items.IndexOf（_currentMediaPlaybackItem）; 

解决方案

嗨SHAKIR820，

>>但是，MediaPlaybackList.Items.IndexOf（_currentItem）始终返回-1。为什么？我需要帮助。 

这种行为的原因是_currentMediaPlaybackItem对象不是你在列表中添加
的exactMediaPlaybackItem对象。

_currentMediaPlaybackItem对象，我们将其称为
A，是从目标文件创建的新对象。

然后您在for循环中创建了一个MediaPlaybackItem列表。在此列表
中，有一个从目标文件创建的新MediaPlaybackItem对象。我们称之为
B 。

虽然 A 和
B 都是从相同的文件，但它们是两个不同的对象。
A 不在列表中， B 会添加到列表中。因此，当您搜索
A 时，它返回-1表示该项目在列表中不存在。（
IList< T> .IndexOf（T）
方法 ）

最好的问候，

罗伊

I am developing a music player. I need to get the index for a specific item from the MediaPlaybackList. But MediaPlaybackList.Items.IndexOf(_currentItem) always return -1. Why ?? I need help. 

MediaPlaybackItem _currentMediaPlaybackItem = new MediaPlaybackItem(MediaSource.CreateFromStorageFile(song.SongFile));
            MediaPlaybackList playbacklist = new MediaPlaybackList();
if (MusicPlayedFrom == "MyMusicPage")
            {
                CurrentlyPlayingSong = song;
                foreach (var item in Songs)
                {
                    MediaPlaybackItem playbackItem = new MediaPlaybackItem(MediaSource.CreateFromStorageFile(item.SongFile));
                    playbacklist.Items.Add(playbackItem);
                }
}
MediaPlayer.Source = playbacklist;
            var count = playbacklist.Items.Count;
            var index = playbacklist.Items.IndexOf(_currentMediaPlaybackItem);

解决方案

Hi SHAKIR820,

>> But MediaPlaybackList.Items.IndexOf(_currentItem) always return -1. Why ?? I need help. 

The reason for this behavior is that the _currentMediaPlaybackItem object is not the exactlyMediaPlaybackItem object you added in the list.

The _currentMediaPlaybackItem object, we call it as A, is a new object created from the target file.

Then you have created a list of MediaPlaybackItems in a for loop. In this list there is a new MediaPlaybackItem object created from the target file. Let’s call it B.

Although A and B are all created from the same file but they are two different object. A is not in the list and B is added to the list. So when you search for A , it return -1 that means the item doesn’t exist in the list.( IList<T>.IndexOf(T) Method)

Best regards,

Roy

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