title: Android - event when user backs out of the app?
body: <p>I'm making an app and I need to store the data on the app when the user backs out of it.
  Currently, when the user presses the home button the event <code>onPause</code> is called - so I can run a method to save data here.</p>
  
  <p>However, when the user backs out of the app via the back button on the phone the <code>onPause</code> method doesn't seemed to be called so I cannot save any data; upon opening the app again after backing out of it, the last session is lost.</p>
  
  <p>TL;DR: how can I save data when the user backs out of the app? What event is called when the user backs out?</p>