MotionEvent-Java中的action_move（监听action_up）

Question

Let's say that I have a motion event, that when I hold a key my cannon shoots balls. Everything is okay but I needed to create a while() loop for this inside this event, cause balls were lagging.

The point is here I can't escape this event. The while loop is infinite and I can't listen for ACTION_UP. Is there any way to stop this on ACTION_UP while being in this loop?

EDIT: part of the code:

@Override
public void surfaceCreated(SurfaceHolder holder) {

    game = new Game(holder, resources);
    game.start();
    shootingThread = new Thread(new Runnable() {
        @Override
        public void run(){
            while(running) {
                int size = game.gameLoop.balls.size();
                    if (size == 0) {
                        game.gameLoop.balls.add(new Ball(metrics.widthPixels, metrics.heightPixels, touched_x, touched_y, game.gameLoop.ball_bmp_width, metrics.heightPixels - game.gameLoop.ball_bmp_width / 2));
                    } else if (size > 0 && game.gameLoop.balls.get(size - 1).image_center_y < metrics.heightPixels - game.gameLoop.ball_bmp_width - 50)
                        game.gameLoop.balls.add(new Ball(metrics.widthPixels, metrics.heightPixels, touched_x, touched_y, game.gameLoop.ball_bmp_width, metrics.heightPixels - game.gameLoop.ball_bmp_width / 2));
                }
            // }
        }
    });
    shootingThread.start();

}

@Override
public boolean onTouchEvent(MotionEvent event) {
    // TODO Auto-generated method stub

    touched_x = event.getX();
    touched_y = event.getY();

    int action = event.getAction();
    if (action == MotionEvent.ACTION_DOWN) {
        startShootTime = new Date().getTime();
        running = true;
        shootingThread.run();
        Log.i("", "\n\ndown\n\n");

    } else if (action == MotionEvent.ACTION_MOVE ) {
        touched_x = event.getX();
       touched_y = event.getY();


    } else if (action == MotionEvent.ACTION_UP) {

        Log.i("", "\n\nup\n\n");
        running = false;
    }

    return true;
}

Answer 1

The onTouchEvent method fires events as they come in and should not be blocked. If you want to continuously trigger an action while the user's fingers are down then once you get the ACTION_DOWN event you should kick off a thread (or async task or timer or any other form of action on another thread) which should then add the balls to your game loop. Then in your main thread you'll need to determine if there were changes on the UI and invalidate/draw your updated views.

However, ACTION_MOVE will get fired a lot while the user has their finger down. So you'll have to determine for yourself whether that is fast enough or if you need to move that logic to another thread.

Note that onTouchEvent will fire as fast as you can consume it, so if you run into performance problems it is actually ok to put a small sleep here. You can see documentation of that recommendation here