（1）前台
说是前台，其实音乐的播放都是利用系统后台的 BackgroundMediaPlayer：
BackgroundMediaPlayer.Current.SetUriSource(new Uri("ms-appx:///djlang59_-_Drops_of_H2O_(_The_Filtered_Water_Treatment_).mp3"));
BackgroundMediaPlayer.Current.Play();
可以添加音乐播放状态改变事件：
BackgroundMediaPlayer.Current.CurrentStateChanged += MediaPlayerStateChanged;private async void MediaPlayerStateChanged(MediaPlayer sender, object args
{
await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
switch( BackgroundMediaPlayer.Current.CurrentState )
{
case MediaPlayerState.Stopped:
AppBarBtnPause.IsEnabled = false;
AppBarBtnStop.IsEnabled = false;
break;
case MediaPlayerState.Playing:
AppBarBtnPause.IsEnabled = true;
AppBarBtnStop.IsEnabled = true;BackgroundMediaPlayer.SendMessageToBackground(new ValueSet
{
{"Title", "Drops of H2O"},
{"Artist", "J.Lang"},
});
break;
case MediaPlayerState.Paused:
AppBarBtnPause.IsEnabled = false;
break;
}
});
}
其中 BackgroundMediaPlayer.SendMessageToBackground
方法可以向后台音乐播放程序发送消息，可在后台程序中添加处理事件：
BackgroundMediaPlayer.MessageReceivedFromForeground += BackgroundMediaPlayerOnMessageReceivedFromForeground;private void BackgroundMediaPlayerOnMessageReceivedFromForeground(object sender, MediaPlayerDataReceivedEventArgs e)
{
systemmediatransportcontrol.DisplayUpdater.Type = MediaPlaybackType.Music;
systemmediatransportcontrol.DisplayUpdater.MusicProperties.Title = e.Data["Title"].ToString();
systemmediatransportcontrol.DisplayUpdater.MusicProperties.Artist = e.Data["Artist"].ToString();
systemmediatransportcontrol.DisplayUpdater.Update();
}
（2）后台
这里说的后台是指
SystemMediaTransportControls，也就是按下音量键后顶部弹出的控制音乐播放的控件。
1）新建 Windows Runtime Component 和继承 IBackgroundTask
的后台类
A：Run 方法中可设置 SystemMediaTransportControls
的各个按键属性以及事件的订阅（比如下一曲按钮可不可用，状态更改事件等）
public void Run(IBackgroundTaskInstance taskInstance)
{
systemmediatransportcontrol = SystemMediaTransportControls.GetForCurrentView();
systemmediatransportcontrol.ButtonPressed += SystemControlsButtonPressed;
systemmediatransportcontrol.IsEnabled = true;
systemmediatransportcontrol.IsPauseEnabled = true;
systemmediatransportcontrol.IsStopEnabled = true;
systemmediatransportcontrol.IsPlayEnabled = true;BackgroundMediaPlayer.Current.CurrentStateChanged -= BackgroundMediaPlayerCurrentStateChanged;
BackgroundMediaPlayer.MessageReceivedFromForeground -= BackgroundMediaPlayerOnMessageReceivedFromForeground;
BackgroundMediaPlayer.Current.CurrentStateChanged += BackgroundMediaPlayerCurrentStateChanged;
BackgroundMediaPlayer.MessageReceivedFromForeground += BackgroundMediaPlayerOnMessageReceivedFromForeground;deferral = taskInstance.GetDeferral();
}
B：事件的处理
private void BackgroundMediaPlayerCurrentStateChanged(MediaPlayer sender, object args)
{
if (sender.CurrentState == MediaPlayerState.Playing)
{
systemmediatransportcontrol.PlaybackStatus = MediaPlaybackStatus.Playing;
}
else if (sender.CurrentState == MediaPlayerState.Paused)
{
systemmediatransportcontrol.PlaybackStatus = MediaPlaybackStatus.Paused;
}
}private static void SystemControlsButtonPressed(SystemMediaTransportControls sender, SystemMediaTransportControlsButtonPressedEventArgs args)
{
switch (args.Button)
{
case SystemMediaTransportControlsButton.Play:
BackgroundMediaPlayer.Current.Play();
break;
case SystemMediaTransportControlsButton.Pause:
BackgroundMediaPlayer.Current.Pause();
break;
case SystemMediaTransportControlsButton.Stop:
BackgroundMediaPlayer.Current.Pause();
BackgroundMediaPlayer.Current.Position = TimeSpan.FromSeconds(0);
break;
}
}
2）前台应用添加上一步新建的后台任务
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