Home Button press issue on my app

Question

I'm trying to solve this but couldn't find any answer on SO. My issue is that whenever I'm in my app and I press the home button, my app layout becomes for a second like the wallpaper for my menu on the phone!

Something like this :

I've tried to override the menu button like this:

public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_MENU) {
        this.finish();
    }
    return super.onKeyDown(keyCode, event);
}

But this will not work. Any help will be appreciated.