@Override
 public void onFileDownloaded(String jsonString) {
   if (mListener == null) return;
   Gson gson = new Gson();
   try {
     GasStationJsonWrapper wrapper = gson.fromJson(jsonString, GasStationJsonWrapper.class);
     if ((wrapper.stations == null || wrapper.stations.size() == 0) && !mRepeated) {
       mRepeated = true;
       (new HttpGetTask(this, getUrl())).execute();
     }
     mListener.onGasStationsParsed(wrapper.stations);
   } catch (Exception e) {
     onFailed(e);
   }
 }
 @Override
 public void onFailed(Throwable e) {
   if (mListener == null) return;
   mListener.onGasStationParserFailed(e);
 }