title: Android detect or block floating/overlaying apps
body: <p>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.</p>
  
  <p>My question is: Is it possible to detect or block in Java code any app which draws over my app?</p>