why ImageView can't update before SystemClock.sleep()

Question

I want to show other image in ImageView within 3 second, after that rollover old image. The code:

    OnClickListener oc = new OnClickListener() {
@Override
public void onClick(View v) {
         ImageView iv = (ImageView)v;
         iv.setImageResource(img2_id);
         SystemClock.sleep(3000);
         iv.setImageResource(img1_id);
    }
    }

    myImageView.setOnClickListener(oc);

But it doesn't work? So, am I doing something wrong?

Answer 1

You are blocking the UI thread. Thus during the sleep command, the screen won't refresh. What you need is to schedule a non-blocking delayed call to a function which changes image resource. Here is a modified code that would do such a thing:

Handler mHandler = new Handler(); /*handler declared in your Activity thread, I assume*/

OnClickListener oc = new OnClickListener() {
    @Override
    public void onClick(View v) {
        ImageView iv = (ImageView)v;
        iv.setImageResource(img2_id);

        mHandler.postDelayed(new Runnable(){
            public void Run(){
                iv.setImageResource(img1_id);
            }
        },3000);

    }
}
myImageView.setOnClickListener(oc);