title: Do I need to explicitly setResult to RESULT_CANCELED?
body: <p>I have an activity that expects the user to select an item, but the user can instead choose to click the back button without selecting an item.  This "item selecting" activity is started with startActivityForResult().</p>
  
  <p>I was wondering two things.  First, is it sufficient to only setResult(RESULT_OK) when the item is actually selected, i.e., can I rely upon the result not being set to RESULT_OK if I don't set it explicitly?  </p>
  
  <p>Second, if this isn't sufficient to rely upon the (uninitialized) result, is it okay to call setResult() multiple times, the first time "initializing" the result to RESULT_CANCELED, and then calling SetResult(RESULT_OK) after the user selects an item and before finishing the activity?</p>