title: Android lifecycle issue
body: <p>After reading official documentation about Activity Lifecycle I have an issue - How can I understand in onDestroy(), that my Activity was killed by system or finished by user? I think, at official page it's not fully clear:</p>
  
  <blockquote>
    <p>If an activity is paused or stopped, the system can drop it from
    memory either by asking it to finish (calling its finish() method), or
    simply killing its process. When the activity is opened again (after
    being finished or killed), it must be created all over.</p>
  </blockquote>
  
  <p>But little bit lower wrote about onDestroy() next:</p>
  
  <blockquote>
    <p>Called before the activity is destroyed. This is the final call that
    the activity will receive. It could be called either because the
    activity is finishing (someone called finish() on it), or because the
    system is temporarily destroying this instance of the activity to save
    space. You can distinguish between these two scenarios with the
    isFinishing() method.</p>
  </blockquote>
  
  <p>So, I suggest, that finish() can be called by system during killing my activity( So how can I distinguish - my activity was killed by system or finished by user in onDestroy()?</p>