title: One Activity, multiple Fragments and setRetainInstance
body: <p>in my app I'm using one activity and two fragments. The app uses a layout with a container so the fragments are added via transactions. The first fragment contains a listview and the other fragment a detail view for the listview items.
  Both fragments use setRetainInstance(true). The fragments are added via a replace transaction and addToBackStack(null) is set. The listfragment contains an instance variable which holds some infos for the list. Now I'm changing to detail and press back and the instance variable is null. I read about setRetainInstance and addToBackStack and removed addToBackStack, but even then the instance variable is null. </p>
  
  <p>Does anyone know what I might be doing wrong?</p>
  
  <p>regards,
  Thomas</p>