Windows Phone 8.1 多媒體（3）：音樂

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原文:Windows Phone 8.1 多媒體（3）：音樂

Windows Phone 8.1 多媒體（1）：相片

Windows Phone 8.1 多媒體（2）：視頻

Windows Phone 8.1 多媒體（3）：音樂

 

 

（1）前台

說是前台，其實音樂的播放都是利用系統背景 BackgroundMediaPlayer：

BackgroundMediaPlayer.Current.SetUriSource(new Uri("ms-appx:///djlang59_-_Drops_of_H2O_(_The_Filtered_Water_Treatment_).mp3"));BackgroundMediaPlayer.Current.Play();

可以添加音樂播放狀態改變事件：

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 方法可以向後台音樂播放程式發送訊息，可在背景程式中添加處理事件：

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）後台

這裡說的後台是指 SystemMediaTransportControls，也就是按下音量鍵後頂部彈出的控制音樂播放的控制項。

1）建立 Windows Runtime Component 和繼承 IBackgroundTask 的後台類

A：Run 方法中可設定 SystemMediaTransportControls 的各個按鍵屬性以及事件的訂閱（比如下一曲按鈕可不可用，狀態變更事件等）

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：事件的處理

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）前台應用添加上一步建立的背景工作