code: public void show(FragmentTransaction transaction, String tag){
          mActiveMail = generateDialogFragment();
          mActiveMail.show(transaction, tag);
      }
docs: Show/Create a DialogFragment on the provided FragmentTransaction
  to be executed and shown.
  
  @see android.app.DialogFragment#show(android.app.FragmentTransaction, String)
  @param transaction   the fragment transaction used to show the dialog
  @param tag           the tag for the dialog fragment in the manager