@Override
    public boolean onKeyDown(int keyCode, KeyEvent event)  {
        if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
            // don't write anything here to make back button not work
            }
            return true;
        }

        return super.onKeyDown(keyCode, event);
    }

@Override
public void onBackPressed() {
// don't write anything here to make back button  not work
}

@Override
public void onBackPressed() {
//do nothing
}