title: Where should i implement android audio focus change listener?
body: <p>I am a beginner in android development. please let me support 
  I was developing android music player app. how to stop, pause audio when a phone call arrived or any notification arrived.
  Should I implement audio focus change listener in my main activity or my music service class?
  If it is in the main activity where should I write code (on create)?
  if it is in service class where should I call and create?
  if you find any mistakes in my grammer please ignore.</p>