How to delay a loop in android without using thread.sleep?

Question

I wanted to delay a for loop without using Thread.sleep because that method make my whole application hang. I tried to use handler but it doesn't seems to work inside a loop. Can someone please point out the mistake in my code.

public void onClick(View v) { 
    if (v == start)
    {   
        for (int a = 0; a<4 ;a++) {

         Handler handler1 = new Handler();
         handler1.postDelayed(new Runnable() {

        ImageButton[] all= {btn1, btn2, btn3, btn4};
        btn5 = all[random.nextInt(all.length)];
        btn5.setBackgroundColor(Color.RED);

             @Override
             public void run() {

             }
             }, 1000);
        } 
        }
     }

Basically what I wanted to do is that I got 4 ImageButton and I change each of their background to red by using a loop in order. Thats why I need a delay inside my loop, if not all the ImageButton will just directly turn red without showing which ImageButton turn first.

Answer 1

Your for loop should be:

final ImageButton[] all= {btn1, btn2, btn3, btn4};
Handler handler1 = new Handler();
for (int a = 1; a<=all.length ;a++) {
    handler1.postDelayed(new Runnable() {

         @Override
         public void run() {
              ImageButton btn5 = all[random.nextInt(all.length)];
              btn5.setBackgroundColor(Color.RED);
         }
         }, 1000 * a);
    } 
}

This way it achieves your desired behavior of staggering the color change.

Edited for syntax