當調用UWP中的後臺任務時，RPC服務器不可用（Excep_FromHResult 0x800706BA）

我開發了UWP應用程序，它在後臺播放音頻文件或手機被鎖定。該應用程序工作正常，一切似乎完美的5-10分鐘。之後，當我運行該應用程序時，我無法播放音頻文件，並且獲取了該主題中附帶的例外。但是，如果我重新啓動應用程序，一切都可以正常工作。我已經按照以下步驟操作，並添加了以下代碼和項目來完成此任務。當調用UWP中的後臺任務時，RPC服務器不可用（Excep_FromHResult 0x800706BA）

創建通用項目（視窗通用）
添加以下代碼來發送背景消息

BackgroundMediaPlayer.MessageReceivedFromBackground + = BackgroundMediaPlayer_MessageReceivedFromBackground;
添加了Windows組件運行時（視窗通用）與下面的代碼

新增的切入點和後臺任務在Package.appxmanifest

public sealed class AudioPlayer : IBackgroundTask { 
    private BackgroundTaskDeferral deferral; 
    private SystemMediaTransportControls systemmediatransportcontrol; 
    public void Run(IBackgroundTaskInstance taskInstance) { 
     systemmediatransportcontrol = BackgroundMediaPlayer.Current.SystemMediaTransportControls; 
     systemmediatransportcontrol.ButtonPressed += systemmediatransportcontrol_ButtonPressed; 
     systemmediatransportcontrol.PropertyChanged += systemmediatransportcontrol_PropertyChanged; 
     systemmediatransportcontrol.IsEnabled = true; 
     systemmediatransportcontrol.IsPauseEnabled = true; 
     systemmediatransportcontrol.IsPlayEnabled = true; 
     systemmediatransportcontrol.IsNextEnabled = true; 
     systemmediatransportcontrol.IsPreviousEnabled = true; 

     BackgroundMediaPlayer.Current.CurrentStateChanged += Current_CurrentStateChanged; 
     BackgroundMediaPlayer.MessageReceivedFromForeground += BackgroundMediaPlayer_MessageReceivedFromForeground; 

     deferral = taskInstance.GetDeferral(); 

     taskInstance.Canceled += TaskInstance_Canceled; 
     taskInstance.Task.Completed += Taskcompleted; 
    } 
    void Taskcompleted(BackgroundTaskRegistration sender, BackgroundTaskCompletedEventArgs args) { 
     deferral.Complete(); 
    } 
    private void TaskInstance_Canceled(IBackgroundTaskInstance sender, BackgroundTaskCancellationReason reason) { 
     try { 
      systemmediatransportcontrol.ButtonPressed -= systemmediatransportcontrol_ButtonPressed; 
      systemmediatransportcontrol.PropertyChanged -= systemmediatransportcontrol_PropertyChanged; 

      BackgroundMediaPlayer.Shutdown(); // shutdown media pipeline 
     } 
     catch (Exception) { 
     } 
     deferral.Complete(); 
    } 

    void Current_CurrentStateChanged(MediaPlayer sender, object args) { 
     MediaPlayer player = sender; 
     switch (player.CurrentState) { 
      case MediaPlayerState.Playing: 
       systemmediatransportcontrol.PlaybackStatus = MediaPlaybackStatus.Playing; 
       break; 
      case MediaPlayerState.Paused: 
       systemmediatransportcontrol.PlaybackStatus = MediaPlaybackStatus.Stopped; 
       break; 
     } 
    } 
    void systemmediatransportcontrol_ButtonPressed(SystemMediaTransportControls sender, SystemMediaTransportControlsButtonPressedEventArgs args) { 
     try { 
      switch (args.Button) { 
       case SystemMediaTransportControlsButton.Play: 
        playTrack(); 
        break; 
       case SystemMediaTransportControlsButton.Pause: 
        stopBeforePlaying(); 
        break; 
       case SystemMediaTransportControlsButton.Next: 
        stopBeforePlaying(); 
        nextTrack(); 
        break; 
       case SystemMediaTransportControlsButton.Previous: 
        stopBeforePlaying(); 
        previousTrack(); 
        break; 
      } 
     } 
     catch (Exception) { 
      //Debug.WriteLine(ex.Message); 
     } 
    } 
    void stopBeforePlaying() { 
     MediaPlayer player = BackgroundMediaPlayer.Current; 
     if (player != null) 
      player.Pause(); 
    } 
    void BackgroundMediaPlayer_MessageReceivedFromForeground(object sender, MediaPlayerDataReceivedEventArgs e) { 
     object foregroundMessageType; 
     if (e.Data.TryGetValue(ApplicationSettingsConstants.ChapterStatus, out foregroundMessageType)) { 
      //do something here 
     } 
    } 
    void UpdateUVCOnNewTrack() { 
     //update buttons here 
    } 
    async void playTrack() { 
     MediaPlayer player = BackgroundMediaPlayer.Current; 
     try { 
      if (...) { 
       //load track 
       player.Play(); 
      } 
      else { 
       player.Pause(); 
       MessageService.SendMessageToForeground(ApplicationSettingsConstants.ChapterStatus, (short)ChapterStatus.ForegroundFileNotFound); 
      } 
     } 
     catch (System.IO.DirectoryNotFoundException) { 
      player.Pause(); 
      MessageService.SendMessageToForeground(ApplicationSettingsConstants.ChapterStatus, (short)ChapterStatus.ForegroundFileNotFound); 
     } 
     catch (System.IO.FileNotFoundException) { 
      player.Pause(); 
      MessageService.SendMessageToForeground(ApplicationSettingsConstants.ChapterStatus, (short)ChapterStatus.ForegroundFileNotFound); 
     } 
     finally { 
      UpdateUVCOnNewTrack(); 
     } 
    } 
    void nextTrack() { 
     //load next track 
    } 
    void previousTrack() { 
     //load previous here 
    } 
}

爲什麼我收到上述錯誤？

注意：我已按照Microsoft Sample Background Audio for Windows Phone 8.1 Sample啓用背景音頻播放器。

謝謝！

來源

2016-03-16 ARH

@Mehrzad我試圖格式化，但它沒有工作，謝謝 – ARH

某些情況下可能會導致此異常BackgroundAudio.Reference到Windows-universal-samples/Samples/BackgroundAudio/cs/BackgroundAudio/Scenario1.xaml.cs，功能ResetAfterLostBackground()

後臺任務確實是存在的評論，但它已經消失了。將前景放回初始狀態。不幸的是，任何企圖註銷上BackgroundMediaPlayer.Current東西會與RPC錯誤失敗，一旦後臺任務已丟失..

所以添加此功能，並調用它，你趕上了錯誤。

const int RPC_S_SERVER_UNAVAILABLE = -2147023174; // 0x800706BA 
private void ResetAfterLostBackground() 
{ 
    BackgroundMediaPlayer.Shutdown(); 
    try 
    { 
     BackgroundMediaPlayer.MessageReceivedFromBackground += BackgroundMediaPlayer_MessageReceivedFromBackground; 
    } 
    catch (Exception ex) 
    { 
     if (ex.HResult == RPC_S_SERVER_UNAVAILABLE) 
     { 
      throw new Exception("Failed to get a MediaPlayer instance."); 
     } 
     else 
     { 
      throw; 
     } 
    } 
}

來源

2016-03-18 08:34:03

當調用UWP中的後臺任務時，RPC服務器不可用（Excep_FromHResult 0x800706BA）

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