SoundPlayer.Stop不停止声音播放

Question

我有一个用C#编写的应用程序，它可以播放小的.wav文件。它使用SoundPlayer名称空间中的System.Media类来播放声音，使用调用SoundPlayer.PlaySync方法来播放.wav文件的线程。所有这些都被包装在一个类似于这样的类中：

public class SoundController {

    private object soundLocker = new object();

    protected Thread SoundThread { get; set; }

    protected string NextSound { get; set; }

    protected AutoResetEvent PlayASoundPlag { get; set; }

    protected Dictionary<string, SoundPlayer> Sounds { get; set; }

    protected bool Stopping { get; set; }

    public string SoundPlaying { get; private set; }


    public SoundController() {
        PendingCount = 0;
        PlayASoundFlag = new AutoResetEvent( false );
        Sounds = new Dictionary<string, SoundPlayer>();
        soundLocker = new object();
        Stopping = false;
        SoundThread = new Thread( new ThreadStart( SoundPlayer ) ) { Name = "SoundThread", IsBackground = true };
        SoundThread.Start();
    }

    private void SoundPlayer() {
        do {
            PlayASoundFlag.WaitOne();

            bool soundWasPlayed = false;

            while ( !Stopping && NextSound != null ) {
                lock ( soundLocker ) {
                    SoundPlaying = NextSound;
                    NextSound = null;
                }
                Sounds[ SoundPlaying ].PlaySync();
                lock ( soundLocker ) {
                    SoundPlaying = null;
                    soundWasPlayed = true;
                }
            }
        } while ( !Stopping );
    }

    public bool HasSound( string key ) {
        return Sounds.ContainsKey( key );
    }

    public void PlayAlarmSound( string key, bool stopCurrentSound ) {
        if ( !Sounds.ContainsKey( key ) )
            throw new ArgumentException( "Sound unknown", "key" );

        lock ( soundLocker ) {
            NextSound = key;

            if ( SoundPlaying != null && stopCurrentSound )
                Sounds[ SoundPlaying ].Stop();

            PlayASoundFlag.Set();
        }
    }
}

当我的程序调用PlaySound方法，并且当前正在播放一个声音时，调用Stop方法，但是正在播放的声音实际上并没有停止。我已经在对Stop的调用中放置了跟踪点，并在它之后添加了一行，这样我就可以看到呼叫何时发出，何时返回，同时使用耳机进行监听。很明显，声音会一直播放到最后。

我如何使声音停止可靠地播放？

Answer 1

不幸的是，这是一个混乱的过程，但这是可行的：

 class Program
    {
        static void Main(string[] args)
        {
            SoundPlayerEx player = new SoundPlayerEx(@"c:\temp\sorry_dave.wav");
            player.SoundFinished += player_SoundFinished;

            Console.WriteLine("Press any key to play the sound");
            Console.ReadKey(true);
            player.PlayAsync();

            Console.WriteLine("Press a key to stop the sound.");
            Console.ReadKey(true);
            player.Stop();

            Console.WriteLine("Press any key to continue");
        }

        static void player_SoundFinished(object sender, EventArgs e)
        {
            Console.WriteLine("The sound finished playing");
        }
    }

    public static class SoundInfo
    {
        [DllImport("winmm.dll")]
        private static extern uint mciSendString(
            string command,
            StringBuilder returnValue,
            int returnLength,
            IntPtr winHandle);

        public static int GetSoundLength(string fileName)
        {
            StringBuilder lengthBuf = new StringBuilder(32);

            mciSendString(string.Format("open \"{0}\" type waveaudio alias wave", fileName), null, 0, IntPtr.Zero);
            mciSendString("status wave length", lengthBuf, lengthBuf.Capacity, IntPtr.Zero);
            mciSendString("close wave", null, 0, IntPtr.Zero);

            int length = 0;
            int.TryParse(lengthBuf.ToString(), out length);

            return length;
        }
    }

    public class SoundPlayerEx : SoundPlayer
    {
        public bool Finished { get; private set; }

        private Task _playTask;
        private CancellationTokenSource _tokenSource = new CancellationTokenSource();
        private CancellationToken _ct;
        private string _fileName;
        private bool _playingAsync = false;

        public event EventHandler SoundFinished;

        public SoundPlayerEx(string soundLocation)
            : base(soundLocation)
        {
            _fileName = soundLocation;
            _ct = _tokenSource.Token;
        }

        public void PlayAsync()
        {
            Finished = false;
            _playingAsync = true;
            Task.Run(() =>
            {
                try
                {
                    double lenMs = SoundInfo.GetSoundLength(_fileName);
                    DateTime stopAt = DateTime.Now.AddMilliseconds(lenMs);
                    this.Play();
                    while (DateTime.Now < stopAt)
                    {
                        _ct.ThrowIfCancellationRequested();
                        //The delay helps reduce processor usage while "spinning"
                        Task.Delay(10).Wait();
                    }
                }
                catch (OperationCanceledException)
                {
                    base.Stop();
                }
                finally
                {
                    OnSoundFinished();
                }

            }, _ct);            
        }

        public new void Stop()
        {
            if (_playingAsync)
                _tokenSource.Cancel();
            else
                base.Stop();   //To stop the SoundPlayer Wave file
        }

        protected virtual void OnSoundFinished()
        {
            Finished = true;
            _playingAsync = false;

            EventHandler handler = SoundFinished;

            if (handler != null)
                handler(this, EventArgs.Empty);
        }
    }

那么为什么它“正常”不起作用呢？这是一个众所周知的问题。SoundPlayer是一段“失忆”的代码，如果您不在启动它的线程上取消它，它就不会做任何事情。很多人抱怨这一点，我相信您已经看到，在使用原始wave_out调用或迁移到DirectX (或者使用WPF，使用MediaPlayer控件)方面，很少有解决方案。

这个SoundPlayerEx类有两个属性，可以让您知道声音什么时候结束，或者取消播放异步启动的声音。没有必要创建一个新的线程来工作，使它更容易使用。

尽管扩展代码，这是一个快速和肮脏的解决方案，您的问题。您需要的两个类是SoundInfo类和SoundPlayerEx类，上面的其余代码是一个演示(将wav文件替换为您自己的一个)。

Note这不是一个通用的解决方案，因为它依赖于winmm.dll，因此它不会移植到Mono (不确定Mono是否有SoundPlayer类)。另外，由于它是一个肮脏的解决方案，如果不使用Finished调用，就不会得到PlayAsync事件或属性。