title: Android : GCMIntentReceiver make a notification unless an activity is running
body: <p>So in my application, the user is on some kind of a wait screen and the server may push him result in a few second or in a few minutes.</p>
  
  <p>So I would like the GCMIntentReceiver to check if an activity is running. If it is, I would like to start an other activity. If it's not, it should make a Notification.</p>
  
  <p>But I don't know how to do that ^^</p>