Question

使用MVVM，我有一个包含3个视图模型的窗口。2个呈现数据和一个音频播放器ViewModel。与其中2个用户界面的交互应触发音频设备的“停止命令”，即

PlaybackDevice.Stop();

由于我具有用于“播放”和“停止”的相同按钮，因此可以通过来自同一按钮的同一命令来管理播放/停止事件。但不是任何其他按钮。我试图实例化Player类，并调用一个包含PlaybackDevice.Stop（）的Stop方法；没用，所以我创建了一个静态的PlaybackDevice设备并直接从ViewModels调用它-仍然不起作用。我应该如何实现这一目标？

Player ViewModel：

  #region Commands
        public ICommand PlayStopTrack { get; set; }
       // public ICommand 
        #endregion

        #region Classes

        HardwareManager hm = new HardwareManager();
        public Mp3FileReader TrackMp3 { get; set; }
        public WaveFileReader TrackWav { get; set; }
        #endregion
        #region Properties

        private static string trackToPlay;

        public static string TrackToPlay
        {
            get { return trackToPlay; }
            set
            {
                trackToPlay = value;
            }
        }

        //public string TrackToPLay { get; set; }

        public string DidTrackStop{get;set;}

        public static WasapiOut PlaybackDevice { get; set; }
 public PlayerVM()
        { 
PlayStopTrack = new RelayCommand(PlayPressed, CanExecute);
}

 private bool CanExecute(object obj)
        {
            return true;
        }

//take the default audio device
 void GetDevice()
        {
            Console.WriteLine("Prepare Device");
            if (PlaybackDevice == null)
            {
                PlaybackDevice = hm.InitialiseAudioPlaybackDevice();
            }
        }


 public void PlayTrackFromBeginning(string trackFullPath)
        {

            if (trackFullPath != null )
            {
                string fileExtension = Path.GetExtension(trackFullPath);
                switch (fileExtension)
                {
                    case ".mp3":
                        try
                        {
                            Console.WriteLine("Init Playing");
                        TrackMp3 = new Mp3FileReader(trackFullPath);
                        if (PlaybackDevice == null)
                        {
                            GetDevice();
                            PlaybackDevice.PlaybackStopped += OnPlaybackStopped;



                        }
                        if (PlaybackDevice.PlaybackState == PlaybackState.Stopped)
                        {
                            PlaybackDevice.Init(TrackMp3);
                            PlaybackDevice.Play();
                            GetTrackLength();
                        }

                        //}
                        //catch (Exception e)
                        //{
                        //    MessageBox.Show(e.Message + " 1- " + e.InnerException);
                        //}
                        break;
                    case ".wav":
                        //try
                        //{
                        Console.WriteLine("Init Playing");
                        GetDevice();
                         PlaybackDevice.PlaybackStopped += OnPlaybackStopped;
                        //TODO implement wav reader.
                        TrackWav = new WaveFileReader(trackFullPath);
                        PlaybackDevice.Init(TrackWav);
                        PlaybackDevice.Play();
                        GetTrackLength();
                        //}
                        //catch (Exception e)
                        //{
                        //    MessageBox.Show(e.Message + " - " + e.InnerException);
                        //}
                        break;
                }
                ButtonLabel = "Stop";
            }

//the actual stop method

private void OnPlaybackStopped(object sender, StoppedEventArgs e)
        {
            if (TrackMp3 != null)
            {
                Console.WriteLine("Init StopEvent");
                TrackMp3.Dispose();
                PlaybackDevice.Dispose();
                TrackMp3 = null;
                Position = 0;
                CurrentTime = "00:00";
                isPlaying = false;
            }
            if (TrackWav != null)
            {
                TrackWav.Dispose();
                PlaybackDevice.Dispose();
                TrackWav = null;
                Position = 0;
                CurrentTime = "00:00";
                isPlaying = false;
            }
            ButtonLabel = "Play";
        }

  public void PlayPressed(object o)
        { 
            if (Path.GetExtension(TrackToPlay) == ".mp3")
            {
                if (isPlaying == false
                    && TrackMp3 == null
                    && TrackToPlay != null)
                {
                    PlayTrackFromBeginning(TrackToPlay);

                  //  IsTrackPlaying = true;
                    isPlaying = true;
                    Timer.Start();

                }

                else if (PlaybackDevice.PlaybackState==PlaybackState.Playing)
                {
                    MessageBox.Show("Stopping ama kur!");
                    PlaybackDevice.Stop();
                    isPlaying = false;
                    //Thread.Sleep(1000);
                    // PlayTrackFromBeginning(TrackToPLay);

                }
            }

            if (Path.GetExtension(TrackToPlay) == ".wav")
            {
                if (isPlaying == false
                    && TrackWav == null
                    && TrackToPlay != null)
                {
                    PlayTrackFromBeginning(TrackToPlay);
                   // IsTrackPlaying = true;
                    isPlaying = true;
                    Timer.Start();

                }

                else if (isPlaying == true)
                {
                    PlaybackDevice.Stop();
                    isPlaying = false;
                    //Thread.Sleep(1000);
                    // PlayTrackFromBeginning(TrackToPLay);

                }
            }
        }

Answer 1

我不确定是否正确理解，但我会尽力帮助您。首先，您的PlayPressed方法在哪里？您使用PlayPressed和CanExecute在ctor中实例化了一个RelayCommand，但是我看不到第一种方法的代码？

Answer 2

我解决了Singleton类的问题。这样，我总是使用最初播放音乐并通过另一个ViewModel的“播放/停止”按钮停止音乐的对象。

如何停止从另一个ViewModel的按钮播放音频

2 个答案: