title: onCreate vs. onResume/onRestart bevhaviour regarding member variables
body: <p>When I open an activity I know that I can initialize stuff in the onCreate function.</p>
  
  <p>But what is the behaviour on the OnResume and onRestart function? When are these functions called?</p>
  
  <p>Specifically: I initialize a local member variable in the onCreate function auiqring a reference to a global object. Now, when the user is interrupted, for example, by a call, the activity can be closed. Later, when the user comes back to my view, what is the status of the already initiliazed variable?
  Do I have to reinitialize everything in the onResume/onRestart functions? So what would be the functional difference opposed to onCreate?</p>