title: How To Reuse Activity on Top of Stack
body: <p>My app has a single entry activity called "Main". In "Main" I call one of three
     other activities A, B, or C (based on a preference) and then immediately exit/finish 
     "Main" so that only A, B, or C are active.</p>
  
  <p>I also have a permanent notification in the notification bar 
     that users can pull down (at any time) to conveniently restart my App (calls intent 
     with "Main" component).</p>
  
  <p>The problem is that if my app is already running and users pull down the notification
     and restart, I get A or B or C running on top of the previous activity (also A, or
     B, or C). How can I avoid this (i.e. reuse the activity on top of the stack)?</p>
  
  <p>I've tried Intent.FLAG_ACTIVITY_* and nothing seems to work. I've tried launchModes<br>
     in the Manifest and it also didn't seem to work. Any ideas? Any help appreciated....jh</p>