Question

我正在尝试在ActionListener中停止一个计时器。以下是我正在尝试做的代码。我想在actionPerformed方法中遇到某个条件时停止我创建的计时器。 timer.stop（）不起作用，编译器不允许我这样做。

任何帮助。建议，建议会非常有帮助。

public class ToggleAnnotationsAction extends IdentifiedMultiAction {
    //This status indicates if the Toggle action has been completed

/**
 * Defines the toggling direction of a <code>ToggleAnnotationAction</code> instance.
 */
public static enum Direction {FORWARD, BACKWARD};
private Direction myDir;

/**
 * Create an action with the direction presets given by the provided <code>Enum</code>.
 * 
 * @param dir An <code>Enum</code> defined in this class which maps to the correct direction of toggling
 * @see behaviors.multiact.IdentifiedMultiAction#IdentifiedMultiAction(Enum)
 */
public ToggleAnnotationsAction(Direction dir) {
    super(dir);
    this.myDir = dir;
}

/**
 * Performs the toggling, moving the audio position to the next/previous annotation.
 * 
 * Afterward sends an update to all <code>UpdatingActions<code>.
 *
 * Since the waveform display autonomously decides when to paint itself, this action may not result in an instant visual change.
 * 
 * <p>Prints warnings if an appropriate Annotation could not be found, despite the action being enabled.
 * 
 * @param e The <code>ActionEvent</code> provided by the trigger
 */
public void actionPerformed(ActionEvent e) {
    //Reset Status to 0 
    status =0;


    Annotation ann = findAnnotation(myDir, CurAudio.getMaster().framesToMillis(CurAudio.getAudioProgress()));
    if(ann == null) {
        System.err.println("It should not have been possible to call " + getClass().getName() + ". Could not find matching annotation");
    }
    else {
        final long approxFrame = CurAudio.getMaster().millisToFrames(ann.getTime());
        final long curFrame = CurAudio.getAudioProgress();
        if(approxFrame < 0 || approxFrame > CurAudio.getMaster().durationInFrames() - 1) {
            GiveMessage.errorMessage("The annotation I am toggling to isn't in range.\nPlease check annotation file for errors."); 
            return;
        }

             Timer timer = new Timer(10, new ActionListener() {
                 private long panFrame = curFrame;
                 private long endFrame = approxFrame;
                 public void actionPerformed(ActionEvent evt) {

                     if(myDir == Direction.FORWARD){
                         if (panFrame >= endFrame) {

                             //How do i Stop my timer here ? 
                             return;
                         }
                         CurAudio.setAudioProgressWithoutUpdatingActions(panFrame);
                         panFrame += 4000;
                    }
                 else if(myDir == Direction.BACKWARD){
                     if (panFrame <= endFrame) {

                        // How do i Stop my timer here ? 
                         return;
                     }
                     CurAudio.setAudioProgressWithoutUpdatingActions(panFrame);
                     panFrame -= 4000;
                }
             }

         }
         );

         timer.start();

      }
    MyFrame.getInstance().requestFocusInWindow();
}


/**
 * A forward (backward) <code>ToggleAnnotationsAction</code> should be enabled only when audio is open, not playing, and when there is an annotation following (preceding) the current position.
 */
@Override
public void update() {
    if(CurAudio.audioOpen()) {
        if(CurAudio.getPlayer().getStatus() == PrecisionPlayer.Status.PLAYING) {
            setEnabled(false);
        }
        else {
            double curTimeMillis = CurAudio.getMaster().framesToMillis(CurAudio.getAudioProgress());
            if(findAnnotation(myDir, curTimeMillis) != null) {
                setEnabled(true);
            }
            else {
                setEnabled(false);
            }
        }
    }
    else {
        setEnabled(false);
    }
}

/**
 * Finds the next/previous <code>Annotation</code> relative to a certain audio position in milliseconds.
 * 
 * @param dir The direction of movement
 * @param curTimeMillis The present time in milliseconds
 * 
 * @return In principle, the <code>Annotation</code> after/before <code>curTimeMillis</code>
 */
private Annotation findAnnotation(Direction dir, double curTimeMillis) {
    Annotation[] anns = AnnotationDisplay.getAnnotationsInOrder();
    if(myDir == Direction.FORWARD) {
        for(int i = 0; i < anns.length; i++) {
            if(anns[i].getTime() - curTimeMillis > 1) {
                return anns[i];
            }
        }
    }
    else {
        for(int i = anns.length - 1; i >= 0; i--) {
            if(curTimeMillis - anns[i].getTime() > 1) {
                return anns[i];
            }
        }
    }
    return null;
}

}

先谢谢克里希南

Answer 1

也可能：

final Timer timer = new Timer(10, null);
timer.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent evt) {
        (as in the question, except that you can refer to timer here)
    }
});

或者，使用事件对象获取源（并投射它， boo ）：

final Timer timer = new Timer(10, new ActionListener() {
    public void actionPerformed(ActionEvent evt) {
        ((Timer)evt.getSource()).stop();
    }
});

或者，将计时器保存在实例变量中，您可以从处理程序中引用它，或让处理程序在您的类上调用一个可以停止/启动它的方法。

Answer 2

有趣的问题。

你必须让Timer最终在你要阻止它的匿名ActionListener中访问它。但匿名的ActionListener仍然无法编译，因为Timer还没有被初始化。

请注意，定时器可能不是您的最佳选择。但为了使这个工作原样，我将Timer包装在一个内部类中。

在ToggleAnnotationsAction.actionPerformed()方法中添加以下行：

MyTimer timer = new MyTimer();
timer.start();

然后可以使用这样的类，用Timer的ActionListener代码替换我的简单ActionListener代码：

private class MyTimer implements ActionListener{
  private Timer timer;

  private MyTimer(){
     timer = new Timer(10, this);
  }

  public void start(){
     timer.start();
  }

  public void stop(){
     timer.stop();
  }

  public void actionPerformed(ActionEvent e){
     if(isTimeToStop()){
        stop();
     }
  }

  public boolean isTimeToStop(){
     return true;
  }
}

从Action Listener内部停止一个swing计时器

2 个答案: