title: Starting child activity from notification
body: <p>I have an activity A, the base UI of a music player, containing lists of songs, ecc. It is bound to a Service. This Service is the one that creates a notification for the songs. </p>
  
  <p>Activity B has A as a parent, only has textViews with the song information. When started form A, B also binds to that service as A unbinds, and viceversa again when pressing "back" button (Whoever has Spotify on their phones, A is basically the whole app, B is only the screen showing you the album cover and playback buttons).</p>
  
  <p>B's onCreate and binding to the music Service obviously doesn't kill A, as it can return to it easily, but B does get created every time when called from A, and destroyed if user returns to A.</p>
  
  <p>As I'm listening to music in the background, the notification is of course supposed to take me from wherever I am (whether I'm currently on A, or on any other app on my phone), to B which has the music info and playback controls.</p>
  
  <p>So essentially I want to start B by clicking on the notification, and have A ready to get back to. Instead, what's happening is that B gets created while A (whether in the foreground or not) gets destroyed, killing the service with it as well. B is started but...has nothing.</p>
  
  <p>Which flags are needed for the intent and pendingIntent that I have to pass to the notification's .setContentIntent()? Many are the combinations I've tried, with FLAG_ACTIVITY_SINGLE_TOP or FLAG_ACTIVITY_CLEAR_TOP, and yet such a seemingly simple thing seems to be so hard. </p>