How can I use invalidate() in a for-loop

Question

I want to display a shot for a game I'm working on. But the canvas just invalidate at the end of my for-loop. It's the same problem like here Canvas do not update (invalidate) until whole while loop ends But the answer doesn't work for me. How can I invalidate my canvas in this case?:

else if (event.getX() > 1150 && event.getX() < 1300 
          && event.getY() > 550 && event.getY() < 700)
  {
    System.out.println("Schuss");
    final ArrayList<Shot> positions = game.shot(100, 45, canvas);
    new Thread(new Runnable()
    {
        public void run()
        {
            for (int i = 0; i < positions.size(); i++)
            {
                game.setCurrentShot(positions.get(i));
                System.out.println(i);
                canvas.postInvalidate();
            }       
        }
    }).start();
}

In the shot-function I calculate all positions. The shot will pass and then I want to display thoos positions on my canvas, but that dosen't work.

I think its because you are in another thread but the canvas is in ui thread — Adnan Temur, Oct 11 '19 at 14:57

score 0 · Accepted Answer · answered Oct 11 '19 at 12:57

Try this:

else if (event.getX() > 1150 && event.getX() < 1300 && event.getY() > 550 && event.getY() < 700)
{
    System.out.println("Schuss");
    final ArrayList<Shot> positions = game.shot(100, 45, canvas);
    YourActivity.this.runOnUiThread(new Runnable() {
        public void run() {
            for (int i = 0; i < positions.size(); i++)
            {
                game.setCurrentShot(positions.get(i));
                Log.d("YourApp", "i = "+i);
                canvas.invalidate();
            }
        }
    });
}

try both invalidate and postInvalidate and see any difference — 10101101, Oct 11 '19 at 23:15

How can I use invalidate() in a for-loop

1 Answers1