/**
  * 根据 RefreshToken 获取
  *
  * @param refreshCode RefreshToken
  */
 public Observable<LoginData> refreshToken(String refreshCode) {
   return mAccountApi
       .refreshToken(
           Constants.APP_KEY,
           Constants.APP_SECRET,
           REQUEST_REDIRECT_URI_OFFICIAL,
           REQUEST_GRANT_TYPE_REFRESH,
           refreshCode)
       .compose(flatResult());
 }