code: public void show(FragmentManager manager, String tag){
          mActiveMail = generateDialogFragment();
          mActiveMail.show(manager, tag);
      }
docs: Show/Create a DialogFragment on the provided FragmentManager with
  the given tag.
  
  @see android.app.DialogFragment#show(android.app.FragmentManager, String)
  @param manager       the fragment manager used to add the Dialog into the UI
  @param tag           the tag for the dialog fragment in the manager