处理异常 HTTP 请求Flutter

我想用一些错误消息来处理http请求抖动，但我在这里收到了太多错误.我只是根据这个建议做的，但对我不起作用.拜托，有没有人，帮帮我 下面是我调用API的函数

getData(data, apiUrl) async {
    var tempUrl = _url + apiUrl + await _getToken();
    Uri uri = Uri.parse(tempUrl);
    var fullUrl = uri.replace(queryParameters: data);
    var res;
    try {
      var response = await http.get(fullUrl, headers: _setHeaders()).timeout(
          const Duration(seconds: 60));
      print(response.statusCode);
      if (response.statusCode != 200) {
        res = {
          "success": false,
          "status": response.statusCode,
          "message": _returnResponse(response)
        };
      }
      else {
        res = response;
      }
    }
    on SocketException {
      throw FetchDataException('No Internet connection');
    }
    on TimeoutException catch (e) {
      res = {
        "success": false,
        "status": response.statusCode,
        "message": "Connection timeout"
      };
    } on Error catch (e) {
      print('Error: $e');
    }

    return res;
  }

这是我对除200之外的其他对象的返回响应

dynamic _returnResponse(http.Response response) {
    switch (response.statusCode) {
      case 400:
        throw BadRequestException(response.body.toString());
      case 401:
      case 403:
        throw UnauthorisedException(response.body.toString());
      case 500:
      default:
        throw FetchDataException(
            'Error occured while Communication with Server with StatusCode : ${response
                .statusCode}');
    }
  }

这是我从StackOverflow和其他论坛得到的app_exception.dart

class AppException implements Exception {
  final _message;
  final _prefix;

  AppException([this._message, this._prefix]);

  String toString() {
    return "$_prefix$_message";
  }
}

class FetchDataException extends AppException {
  FetchDataException([String message])
      : super(message, "Error During Communication: ");
}

class BadRequestException extends AppException {
  BadRequestException([message]) : super(message, "Invalid Request: ");
}

class UnauthorisedException extends AppException {
  UnauthorisedException([message]) : super(message, "Unauthorised: ");
}

class InvalidInputException extends AppException {
  InvalidInputException([String message]) : super(message, "Invalid Input: ");
}

我试了这么多建议，但一点也不管用

我犯了这个错误

错误:‘SocketException’不是类型. 关于SocketException{ ^^

错误:"TimeoutException"不是类型.