title: onCreate is called when back button in action bar is pressed
body: <p>My app has 2 main activities, one of which is launched from the main activity.</p>
  
  <p>I'm wondering why <code>onCreate()</code> is being called when I return to the main activity after pressing the back button on the navigation bar of the subactivity.</p>
  
  <p>This does not happen if I press the physical back button.</p>