multithreading - Thread.Sleep() Android UI

Question

I'm working on a memory game for Android and I'm having a problem. When the user taps the second image - if the images are not the same I want the second image to show for 1, 2 seconds.

What I've tried is to sleep for 1-2 sec. the UI thread after the second image is activated - but this doesn't seem to work - the second image doesn't seem to show! (only the first images is showed)

Here's my code:

public void whenTapedImage(View v, int position)
{
    i++;
    ImageView imgV=(ImageView)v;
    if(i%2!=0)
    {
        firstClick=position;
        imgV.setImageResource(im.images.get(firstClick));           
    }
    else
    {   
        secondClick=position;
        imgV.setImageResource(im.images.get(secondClick));                      
        try {
            Thread.currentThread().sleep(1000);
            if(!(im.images.get(firstClick).equals(im.images.get(secondClick))))
            {
                Toast.makeText(easyGame.this, "Try Again!", Toast.LENGTH_SHORT).show();
                im.notifyDataSetChanged();
                gridview.setAdapter(im);
                gridview.invalidate();
                aux=player1Turn;
                player1Turn=player2Turn;
                player2Turn=aux;
            }
            else{
                done=done+2;
                ImageAdapter.keepVisibleViews.add(firstClick);
                ImageAdapter.keepVisibleViews.add(secondClick);
                if(player1Turn==true)
                {
                    player1Score++;
                    String score=Integer.toString(player1Score);
                    score1.setText(score);
                }
                if(player2Turn==true)
                {
                    player2Score++;
                    String score=Integer.toString(player2Score);
                    score2.setText(score);
                }
            }   
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }   
    }           
}

What am I doing wrong?

Answer 1

You must not sleep the UI thread as this would prevent android from delivering any other events to your activity's UI.

Instead, do something such as use a timer and have the timer's method use the run on ui thread facility to make the desired postponed change.

For robustness you may need to implement a state machine (either formally, or in effect) to keep track of what is supposed to be happening - you'll need to decide if the current delay should be aborted or enforced if another button is pushed, and make the state machine treat that appropriately.