title: Android call activity B's method from A's thread
body: <p>I have a main Activity A, in which I create a background thread to load data from db. After the loading is done, I want to update the list which might have been already shown in a child activity B (If user has navigated to B in the meanwhile). If user hasnt yet navigated to B, its not an issue. </p>
  
  <p>But how to update B's list once thread in A has finished?</p>
  
  <p>B is a child of A.</p>
  
  <p>Thanks,</p>