Android detect or block floating/overlaying apps

Question

Android enables apps to draw over other apps with android.permission.SYSTEM_ALERT_WINDOW and it's called a floating/overlaying app. For example Facebook Messenger has always visible chat bubbles at the edges of screen.

My question is: Is it possible to detect or block in Java code any app which draws over my app?

Answer 1

There is a View#onFilterTouchEventForSecurity() method you can override to detect if the motion event has the FLAG_WINDOW_IS_OBSCURED. This will let you know if something is drawn on top of your view.

@Override
public boolean onFilterTouchEventForSecurity(MotionEvent event) {
    if ((event.getFlags() & MotionEvent.FLAG_WINDOW_IS_OBSCURED) == MotionEvent.FLAG_WINDOW_IS_OBSCURED){
        // show error message
        return false;
    }
    return super.onFilterTouchEventForSecurity(event);
}

If you just want to protect your app from tap jacking due to another app drawing over your app you can add setFilterTouchesWhenObscured to your views via XML or programmatically.