how to use a swing timer to start/stop animation

Question

Could someone teach me how to use a swing timer with the following purpose:

I need to have a polygon that begins being animated(simple animation such as rotating) when I click the mouse; and stops animating when I click again.

I do not have problems understanding the way the MouseListener works, but with the actual animation. I tried simulating the animation with a while block inside the paint() method where I would draw, erase and redraw the polygon(to simulate a rotation for example), but inside the while, the applet would not listen to the clicks. It would listen only after the while. I would need the swing timer to break the while when I click the mouse.

Solution 1

import javax.swing.Timer;

Add an attribute;

Timer timer; 
boolean b;   // for starting and stoping animation

Add the following code to frame's constructor.

timer = new Timer(100, new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent ae) {
        // change polygon data
        // ...

        repaint();
    }
});

Override paint(Graphics g) and draw polygon from the data that was modified by actionPerformed(e).

Finally, a button that start/stop animation has the following code in its event handler.

if (b) {
    timer.start();
} else {
    timer.stop();
}
b = !b;

Solution 2

This example controls a javax.swing.Timer using a button, while this related example responds to a mouse click. The latter example reverses direction on each click, but start/stop is a straightforward alteration.

Solution 3

The applet won't listen to clicks because the main thread (the Event Dispatch Thread, EDT) is within the while-loop and isn't listening to your clicks.

You need another thread. (try using SwingWorker http://download.oracle.com/javase/tutorial/uiswing/concurrency/worker.html)

So, the SwingWorker will do the while-loop in the background, publishing results to make your polygon move.

And the EDT can then focus on any events (like clicks). You can then just use the click-event to kill the SwingWorker if you want to stop it.

Good luck