类型'List<dynamic>‘不是'List<Parking>’的子类型

Question

我正在调用一个API，但是我一直试图正确地解析这个JSON响应，但是我没有能够解决这个问题。我调用API，并希望显示数据，但我得到的错误类型'List‘不是'List’或返回'null‘的子类型。我不知道我做错了什么。守则如下：

class Parking {
  String name;
  String adress;
  String description;
  int totalParkingLots;
  int totalFreeParkingLots;
  int latitude;
  int longitude;
  int parkingFees;
  String companyId;
  String status;

  Parking(
      {
      this.name,
      this.adress,
      this.description,
      this.totalParkingLots,
      this.totalFreeParkingLots,
      this.latitude,
      this.longitude,
      this.parkingFees,
      this.companyId,
      this.status,
    });

  Parking.fromJson(Map<String, dynamic> json) {
    name = json['Name'];
    adress = json['Adress'];
    description = json['description'];
    totalParkingLots = json['totalParkingLots'];
    totalFreeParkingLots = json['totalFreeParkingLots'];
    latitude = json['latitude'];
    longitude = json['longitude'];
    parkingFees = json['ParkingFees'];
    companyId = json['companyId'];
    status = json['Status'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['Name'] = this.name;
    data['Adress'] = this.adress;
    data['description'] = this.description;
    data['totalParkingLots'] = this.totalParkingLots;
    data['totalFreeParkingLots'] = this.totalFreeParkingLots;
    data['latitude'] = this.latitude;
    data['longitude'] = this.longitude;
    data['ParkingFees'] = this.parkingFees;
    data['companyId'] = this.companyId;
    data['Status'] = this.status;
    return data;
  }
}

  static Future<List<Parking>> getparkings() async {
    List<Parking> _parkings = [];
    try {
      final uri = Uri.parse(ApiManager.parkingsAPIURL);
      final headers = {'Content-Type': 'application/json'};
      var response = await http.Client().get(
        uri,
        headers: headers,
      );

      int statusCode = response.statusCode;
      print(statusCode);
      var jsonResp = jsonDecode(response.body);

       if (jsonResp != null) {
          _parkings = jsonResp.map((item) => Parking.fromJson(item)).toList();
        }
        return _parkings;
    } catch (e) {
       print(e);
    }
  }

我几乎可以肯定API调用和响应的问题，因为我没有正确地解析JSON数据，但可能是我错了，还有别的问题。

Answer 1

它们是正确的，JSON响应没有什么问题，就像@mmcdon20提到的那样，由于某些原因，Flutter无法在map()函数中检测到正确的返回类型。但我猜这与jsonResp有关，因为它是dynamic类型，而dynamic实际上没有map()函数。

但是现在，要解决这个问题，只需将返回类型转换为map()函数，如下所示：

_parkings = jsonResp.map<Parking>((item) => Parking.fromJson(item)).toList();