@Override
 protected void onPostExecute(ResultType result) {
   activity.setBusy(false);
   if (exception == null) {
     handleResult(result);
   } else {
     handleError(exception);
   }
 }
 protected void handleError(Exception exception) {
   activity.showError(exception);
 }
 @Override
 protected void onPreExecute() {
   activity.setBusy(true);
 }