title: How do you build an Android back stack when an activity is started directly from a notification?
body: <p>I have two activities:</p>
  
  <p>Activity A - list of items<br/>
  Activity B - detail view of an item</p>
  
  <p>Normally, a user opens the app and Activity A is launched.  A user sees a list of items, clicks one, and Activity B is started to display the item detail.</p>
  
  <p>Activity B can also be started directly from clicking on a notification.  In this case there is no back stack.</p>
  
  <p>How can I make it so that when Activity B is started directly from a notification, the user can click the Back button and go to Activity A?</p>