title: How will android activity be "restored" after its process is killed?
body: <p>As it is said in the Dev Guide Activities could be <em>restored</em> after "the App process is killed" and "User navigates to the Activity". First of all, I have never seen such thing happened. It doesn't seem that I can "navigates back" to an Activity when its process is killed, the Activity is simply gone from the stack after the process is gone.</p>
  
  <p>If such thing is to happen, how exactly it will happen?</p>
  
  <p>And I saw a weird but good thing is that:
  There is one <code>Activity A1</code> which starts <code>Activity A2</code> of another App. Now <code>A2</code> is the foreground activity. When memory gets low, at least on emulators(where I can easily eat up the RAM), <code>A2</code> will be killed instead of <code>A1</code>.</p>
  
  <p>What I fear is something like this for example:
  My App have two Activities on the stack, and we call them <code>A0</code> and <code>A1</code>. And <code>A1</code>, again, launched <code>Activity A2</code> of another App. When <code>A0</code> was about to launch <code>A1</code>, it gives <code>A1</code> a reference to a data object <code>D</code>. Now if process for <code>A0</code> and <code>A1</code> is killed while A2 is in foreground, <code>D</code> is lost, too. When A2 has finished, it seems at least <code>A1</code> will need to be restored. And thus <code>A1</code> will have to handle the restoration of <code>D</code>. And what's more A1 will have to find a way to tell the still-dead <code>A0</code> the reference to the restored <code>D</code>. This is complicate or I have walked the wrong way?</p>