title: How to preserve current session after opening app from background
body: <p>I installed my music app into my phone using <code>flutter run</code> and now I'm testing it. What I don't like is when I press back button on my phone, the app goes to background (but continues plaing music). But when I reopen it from background, the whole app restarts itself and the player and every change in the app is restored to the original state (playback stops). Is there a way to just continue with the current session and not restart session when switching the app from background?</p>
  
  <p>The second question might be answered somewhere, I just wonder if there is similarly a way to save the state and restore it even if the app is completely closed and then freshly started?</p>