Java : ignore single click on double click?

问题:

can anyone think of a good way to ignore the single click that comes with a double-click in Java ?

I'm looking to have different behaviors for each such that:

• single-click paints crosshairs on the click point
• double-click selects an object on the screen, but should not paint crosshairs on the click point

... can anyone think of a way to do this ? Some sort of timer set-up maybe ? An ideas appreciated :-)

<disclaimer> ...and yes, I know I'm committing a most heinous usability / UI faux pas. </disclaimer>

EDIT #2:

Even though this works the delay due to the timer is maddening - I'm abandoning this solution, and using middle-click for selection instead of double-click...

EDIT:

Thanks cgull - this is what I was able to come up with given your confirmation that there's no easy way to do this (note that if I set the timer < 200 odd racing is seen between the click & the timer, but as long as I set this to a value > 200 things work just peachy) :

public void mouseClicked(MouseEvent e) {
    System.out.println( "Click at (" + e.getX() + ":" + e.getY() + ")" );
    if (e.getClickCount() == 2) {  
        System.out.println( "  and it's a double click!");
        wasDoubleClick = true;
    }else{
        Integer timerinterval = (Integer) 
          Toolkit.getDefaultToolkit().getDesktopProperty(
                      "awt.multiClickInterval");
        timer = new Timer(timerinterval.intValue(), new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                if (wasDoubleClick) {
                    wasDoubleClick = false; // reset flag
                } else {
                    System.out.println( "  and it's a simple click!");
                }
            }    
        });
        timer.setRepeats(false);
        timer.start();
    }
}

回答1:

Indeed you'll need to set up a Timer in your overridden mouseClicked() method of your MouseAdapter to detect the time interval between the two clicks. The default interval in ms can be found by querying Toolkit.getDefaultToolkit().getDesktopProperty("awt.multiClickInterval"). If another mouse click is detected before the timer expires, then you have a double-click, else once the timer expires, you can process the single-click.

回答2:

Actually I think there is a simpler solution (use InputEvent's getWhen() method):

class DCListener extends MouseAdapter{

    private long maxTimeBetweenClicks; // in millis
    private long firstClickTime=0;
    private Runnable eventHandler;

    public DCListener(long maxTimeBetweenClicks,Runnable eventHandler){
        this.maxTimeBetweenClicks=maxTimeBetweenClicks;
        this.eventHandler=eventHandler;
    }

    public void mouseClicked(MouseEvent e){

        if((e.getWhen()-firstClickTime)<=maxTimeBetweenClicks){
            firstClickTime=0; // 3 clicks are not 2 double clicks
            eventHandler.run();
        }else{
            firstClickTime=e.getWhen();
        }

    }
}

回答3:

Have you tried implementing the MouseListener interface already?

I think MouseEvent has a click count method ( or property ) to know that.

I bet you have gone through that already, so what is the problem you're facing there?

Probably what you can do is to code the time interval elapsed between a single and a double click with a thread or something.

So a single click will only be valid if another click is not issued in let's say 300 ms. ( something configurable )

The idea is:

public void listen for the single click() 
    if (  in x time there has not been another click  ) 
    then 
        we have a single click
        proceed with your single click handling
    else 
        we have a double click
       proceed with your double click handling

Or something like that.

回答4:

An alternative solution:

I figured out this before I found the solution in this question. The idea is the same, use a timer, although more complicated :).

Use SwingWorker:

class BackgroundClickHandler extends SwingWorker<Integer, Integer> {
  @Override
  protected Integer doInBackground() throws Exception {
    Thread.sleep(200);
    // Do what you want with single click
    return 0;
  }

}

In mouseClicked() method you can do something like this:

 if (event.getClickCount() == 1) {
  // We create a new instance everytime since
  // the execute() method is designed to be executed once
  clickHandler = new BackgroundClickHandler();

  try {
    clickHandler.execute();
  } catch(Exception e) {
    writer.println("Here!");
  }
}

if (event.getClickCount() == 2) {
  clickHandler.cancel(true);

  //Do what you want with double click
}

I hope it be useful.