未处理的异常：“String”类型不是“Map<String, dynamic>”类型的子类型

Question

我不确定发生了什么，因为我的代码工作正常，但突然停止工作，我认为我没有改变任何与此相关的内容。我已经坚持了两天，无法弄清楚我做错了什么。 API 返回的数据是正确的，返回状态码为 200

我认为该错误与PTWorkoutPlanItem.fromJson() 函数有关。我认为这与PTWorkoutPlanItem 模型中的List<AssignedUsers> 或List<WorkoutPlanItem> 模型没有任何关系，因为当我将它们更改为dynamic 时，错误仍然存​​在

错误提示

[ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: type 'String' is not a subtype of type 'Map<String, dynamic>'

获取数据的代码：

  getPlanData() async {
    var data = PTWorkoutPlanItem.fromJson(
        await get(url: 'pt/workouts/plan/' + planId.toString()));
  }

// Console logged the response here and it is correct, so this function works
Future<dynamic> get({url}) async {
  final response = await http.get(baseUrl + url, headers: headers);
  print(response.statusCode);

  dynamic res = json.decode(response.body);
  return res;
}

模型

class PTWorkoutPlanItem {
  int id;
  String title;
  List<AssignedUsers> assignedUsers;
  List<WorkoutPlanItem> workouts;
  int ptId;

  PTWorkoutPlanItem(
      {this.id, this.title, this.assignedUsers, this.workouts, this.ptId});

  factory PTWorkoutPlanItem.fromJson(Map<String, dynamic> json) {
    return PTWorkoutPlanItem(
      id: json['id'],
      title: json['title'],
      assignedUsers: List.from(json['assignedUsers'])
          .map((item) => AssignedUsers.fromJson(item))
          .toList(),
      workouts: List.from(json['workouts'])
          .map((item) => WorkoutPlanItem.fromJson(item))
          .toList(),
      ptId: json['ptId'],
    );
  }
}

class AssignedUsers {
  int id;
  String title;

  AssignedUsers({this.id, this.title});

  factory AssignedUsers.fromJson(Map<String, dynamic> json) {
    return AssignedUsers(id: json['id'], title: json['title']);
  }
}

class WorkoutPlanItem {
  int id;
  String title;
  int duration;
  int sets;
  int rest;

  WorkoutPlanItem({this.id, this.title, this.duration, this.sets, this.rest});

  factory WorkoutPlanItem.fromJson(Map<String, dynamic> json) {
    return WorkoutPlanItem(
      id: json['id'],
      title: json['title'],
      duration: json['duration'],
      sets: json['sets'],
      rest: json['rest'],
    );
  }
}

这是在 API 中重新调整的内容

{
    "id": 1,
    "title": "Pull day",
    "assignedUsers": [
        {
            "id": 1,
            "title": "josh"
        },
        {
            "id": 2,
            "title": "marus"
        }
    ],
    "workouts": [
        {
            "id": 4,
            "title": "Workout item 4",
            "duration": 10,
            "sets": 3,
            "rest": 3
        },
        {
            "id": 1,
            "title": "Workout item 1",
            "duration": 10,
            "sets": 3,
            "rest": 3
        }
    ],
    "ptId": 1
}

Answer 1

试试这个。我添加了很多类型转换，但最重要的部分是我如何处理 List<dynamic> 并将每个元素转换为 Map<String, dynamic>：

class PTWorkoutPlanItem {
  int id;
  String title;
  List<AssignedUsers> assignedUsers;
  List<WorkoutPlanItem> workouts;
  int ptId;

  PTWorkoutPlanItem(
      {this.id, this.title, this.assignedUsers, this.workouts, this.ptId});

  factory PTWorkoutPlanItem.fromJson(Map<String, dynamic> json) {
    return PTWorkoutPlanItem(
      id: json['id'] as int,
      title: json['title'] as String,
      assignedUsers: (json['assignedUsers'] as List<dynamic>)
          .cast<Map<String, dynamic>>()
          .map((item) => AssignedUsers.fromJson(item))
          .toList(),
      workouts: (json['workouts'] as List<dynamic>)
          .cast<Map<String, dynamic>>()
          .map((item) => WorkoutPlanItem.fromJson(item))
          .toList(),
      ptId: json['ptId'] as int,
    );
  }
}

class AssignedUsers {
  int id;
  String title;

  AssignedUsers({this.id, this.title});

  factory AssignedUsers.fromJson(Map<String, dynamic> json) {
    return AssignedUsers(id: json['id'] as int, title: json['title'] as String);
  }
}

class WorkoutPlanItem {
  int id;
  String title;
  int duration;
  int sets;
  int rest;

  WorkoutPlanItem({this.id, this.title, this.duration, this.sets, this.rest});

  factory WorkoutPlanItem.fromJson(Map<String, dynamic> json) {
    return WorkoutPlanItem(
      id: json['id'] as int,
      title: json['title'] as String,
      duration: json['duration'] as int,
      sets: json['sets'] as int,
      rest: json['rest'] as int,
    );
  }
}

另外，这里有一个 Dart 2.12 兼容版本，其中 required 添加到命名参数，因为它们都不允许是 null 并且没有任何默认值：

class PTWorkoutPlanItem {
  int id;
  String title;
  List<AssignedUsers> assignedUsers;
  List<WorkoutPlanItem> workouts;
  int ptId;

  PTWorkoutPlanItem(
      {required this.id,
      required this.title,
      required this.assignedUsers,
      required this.workouts,
      required this.ptId});

  factory PTWorkoutPlanItem.fromJson(Map<String, dynamic> json) {
    return PTWorkoutPlanItem(
      id: json['id'] as int,
      title: json['title'] as String,
      assignedUsers: (json['assignedUsers'] as List<dynamic>)
          .cast<Map<String, dynamic>>()
          .map((item) => AssignedUsers.fromJson(item))
          .toList(),
      workouts: (json['workouts'] as List<dynamic>)
          .cast<Map<String, dynamic>>()
          .map((item) => WorkoutPlanItem.fromJson(item))
          .toList(),
      ptId: json['ptId'] as int,
    );
  }
}

class AssignedUsers {
  int id;
  String title;

  AssignedUsers({required this.id, required this.title});

  factory AssignedUsers.fromJson(Map<String, dynamic> json) {
    return AssignedUsers(id: json['id'] as int, title: json['title'] as String);
  }
}

class WorkoutPlanItem {
  int id;
  String title;
  int duration;
  int sets;
  int rest;

  WorkoutPlanItem(
      {required this.id,
      required this.title,
      required this.duration,
      required this.sets,
      required this.rest});

  factory WorkoutPlanItem.fromJson(Map<String, dynamic> json) {
    return WorkoutPlanItem(
      id: json['id'] as int,
      title: json['title'] as String,
      duration: json['duration'] as int,
      sets: json['sets'] as int,
      rest: json['rest'] as int,
    );
  }
}

更新：您也可以尝试将您的方法更改为：

Future<Map<String, dynamic>> get({url}) async {
  final response = await http.get(baseUrl + url, headers: headers);
  print(response.statusCode);

  final res = json.decode(response.body) as Map<String, dynamic>;
  return res;
}