線路監聽器事件丟失

Question

我嘗試使用Java剪輯對象播放信號。我開始剪輯，然後等待STOP事件被觸發，直到我繼續線程。我觀察到，如果我退出調用線程（可能發生在我的應用程序中），則聲音不會播放或僅播放第一部分。

但是，大多數情況下，這種方法很好，但是，大約每隔50次，START和STOP事件都不會被觸發，導致當前線程永遠等待。

現在的問題是，我做了一些錯誤的同步，使我失去了事件？

private static volatile boolean isPlaying = false; 
private static final Object waitObject = new Object(); 

public static void playClip(...) 

... 

    Clip clip = (Clip) AudioSystem.getLine(...); 

    clip.addLineListener(new LineListener() { 
     public void update(LineEvent event) { 
      if (event.getType() == LineEvent.Type.STOP) { 
       event.getLine().close(); 
       synchronized (waitObject) { 
        isPlaying = false;       
        waitObject.notifyAll(); 
       } 
      } 
     } 
    }); 


    // start playing clip 
    synchronized (waitObject) { 
     isPlaying = true; 
    } 
    clip.start(); 

    // keep Thread running otherwise the audio output is stopped when caller thread exits 
    try { 
     while (isPlaying) { 
      synchronized (waitObject) { 
       waitObject.wait();      
      } 
     } 
    } catch (InterruptedException e) {   
     e.printStackTrace(); 
    } 
} 

下面是使用新版本 CountDownLatch：

private static volatile CountDownLatch playingFinished = new CountDownLatch(1); 

public static void playClip(...) 

... 
    Clip clip = (Clip) AudioSystem.getLine(...); 
    clip.open(audioInputStream); 

    // use line listener to take care of synchronous call 
    clip.addLineListener(new LineListener() { 
     public void update(LineEvent event) { 
      if (event.getType() == LineEvent.Type.STOP) { 
       event.getLine().close(); 
       playingFinished.countDown(); 
      } 
     } 
    }); 

    clip.start(); 

    try { 
     playingFinished.await(); 
    } catch (InterruptedException e) { 
     e.printStackTrace(); 
    } 

    playingFinished = new CountDownLatch(1); 

我不包括調試，但是他們表示線程在playingFinished.await();掛起，因爲停止事件沒有被解僱，並永遠不會調用playingFinished.countDown();。

Answer 1

幫你自己一個忙，並重寫代碼，以使用CountDownLatch而不是低級的等待通知API。你的問題可能會自行消失。

public void playClip() throws Exception { 
    final CountDownLatch playingFinished = new CountDownLatch(1); 
    final Clip clip = (Clip) AudioSystem.getLine(...); 
    clip.open(...); 
    clip.addLineListener(new LineListener() { 
    public void update(LineEvent event) { 
     if (event.getType() == LineEvent.Type.STOP) { 
     event.getLine().close(); 
     playingFinished.countDown(); 
     } 
    } 
    }); 
    clip.start(); 
    try { 
    playingFinished.await(); 
    } catch (InterruptedException e) { 
    Thread.currentThread().interrupt(); 
    } 
}