Flutter GET请求报错NoSuchMethodError: 对null调用[]方法（depId相关）

我尝试通过GET请求从API获取并展示列表，但持续出现以下错误：

NoSuchMethodError: The method '[]' was called on null.
Receiver: null
Tried calling:

奇怪的是，当前请求并未使用depId，该字段也不在我用于请求的对象中，且之前的请求使用它时完全正常，我不清楚为何会出现null值。

API请求代码 #

static Future<List<Athlete>> getAthletesByTeamKey(
      int depId, int teamId) async {
    try {
      final response = await http.get(
          Uri.parse(
              '$uri/get-athletes-by-team-key?depId=$depId&teamId=$teamId&page=0&length=50'),
          headers: {
            'Authorization': 'Basic ...',
            'Content-Type': 'application/json',
            'Accept': 'application/json'
          });
      print('Response status: ${response.statusCode}');
      print('Response body: ${response.body}');

      if (response.statusCode == 200) {
        if (response.body.isNotEmpty) {
          print('response.body.isNotEmpty');
          List jsonResponse = json.decode(utf8.decode(response.bodyBytes));
          return jsonResponse
              .map((athlete) => Athlete.fromJson(athlete))
              .toList();
        } else if (response.body.isEmpty) {
          print('response.body.isEmpty');
          throw Exception();
        }
      }
    } catch (e) {
      print('catch');
      logger.e(e.toString());
    }
    return getAthletesByTeamKey(depId, teamId, context);
  }

代码会打印print('response.body.isNotEmpty');，随后进入catch块。

Athlete实体类 #

List<Athlete> athleteFromJson(String str) =>
        List<Athlete>.from(json.decode(str).map((x) => Athlete.fromJson(x)));
    String athleteToJson(List<Athlete> data) =>
        json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class Athlete {
  late int id;
  late String firstName;
  late String lastName;
  late String fatherName;
  late int currentMonthPresences;
  late bool isSelected = false;
  late bool hasDebt;
  Department? department;
  Team? team;

  Athlete(
      {required this.id,
      required this.firstName,
      required this.lastName,
      required this.fatherName,
      required this.currentMonthPresences,
      this.isSelected = false,
      required this.hasDebt,
      this.department,
      this.team});

  Athlete.newSelectedAthlete(this.id, this.department, this.team); //I use it for another screen

  factory Athlete.fromJson(Map<String, dynamic> json) => Athlete(
        id: json['id'],
        firstName: json['firstName'],
        lastName: json['lastName'],
        fatherName: json['fatherName'],
        currentMonthPresences: json['currentMonthPresences'],
        hasDebt: json['hasDebt'],
        department: Department.fromJson(json['department']),
        team: Team.fromJson(json['team']),
      );

  Map<String, dynamic> toJson() => {
        'id': id,
        'firstName': firstName,
        'lastName': lastName,
        'fatherName': fatherName,
        'currentMonthPresences': currentMonthPresences,
        'isSelected': isSelected,
        'hasDebt': hasDebt,
        'department': department,
        'team': team,
      };
}

Department实体类 #

class Department {
  int id;
  String depName;

  Department({required this.id, required this.depName});

  factory Department.fromJson(Map<String, dynamic> json) => Department(
        id: json['id'],
        depName: json['depName'],
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "depName": depName,
      };
}

Team实体类 #

class Team {
  final TeamKey teamKey;
  final String teamName;
  final int hidden;
  final User user;
  final String depName;

  Team(
      {required this.teamKey,
      required this.teamName,
      required this.hidden,
      required this.user,
      required this.depName});

  factory Team.fromJson(Map<String, dynamic> json) => Team(
        teamKey: TeamKey.fromJson(json['teamKey']),
        teamName: json['teamName'],
        hidden: json['hidden'],
        user: User.fromJson(json['user']),
        depName: json['depName'],
      );

  Map<String, dynamic> toJson() => {
        'teamKey': teamKey,
        'teamName': teamName,
        'hidden': hidden,
        'user': user,
        'depName': depName,
      };
}

TeamKey实体类（包含depId变量，未使用） #

class TeamKey {
  int depId;
  int teamId;

  TeamKey({required this.depId, required this.teamId});

  factory TeamKey.fromJson(Map<String, dynamic> json) => TeamKey(
        depId: json['depId'],
        teamId: json['teamId'],
      );

  Map<String, dynamic> toJson() => {
        "depId": depId,
        "teamId": teamId,
      };
}

页面展示代码 #

class AthleteScreen extends StatefulWidget {
  const AthleteScreen(this._team, {Key? key}) : super(key: key);
  final Team _team;

  @override
  State<AthleteScreen> createState() => _AthleteScreenState();
}

class _AthleteScreenState extends State<AthleteScreen> {
  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
  final myController = TextEditingController();
  final controller = TextEditingController();

  Future<List<Athlete>>? futureAthletebyTeamKey;
  Future<List<Presence>>? futureGetPresences;
  final List<Athlete> _athlete = [];

  @override
  void initState() {
    futureAthletebyTeamKey = ApiService.getAthletesByTeamKey();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      body: Stack(
        children: [
          SingleChildScrollView(
            child: Column(children: [
              const SizedBox(
                height: 10,
              ),
              FutureBuilder<List<Athlete>>(
                future: futureAthletebyTeamKey,
                builder: (context, AsyncSnapshot snapshot) {
                  if (snapshot.hasData) {
                    List<Athlete> _athlete = snapshot.data;
                    return ListView.builder(
                        shrinkWrap: true,
                        cacheExtent: 34,
                        primary: true,
                        physics: const ClampingScrollPhysics(),
                        padding: const EdgeInsets.only(
                          top: 10,
                          bottom: 56,
                        ),
                        itemCount: _athlete.length,
                        itemBuilder: (BuildContext context, int i) {
                            return CheckboxListTile(
                              title: Column(
                                mainAxisSize: MainAxisSize.min,
                                crossAxisAlignment: CrossAxisAlignment.start,
                                children: [
                                  Row(
                                    children: [
                                      Text(
                                        'ID: ${_athlete[i].id}',
                                        style: const TextStyle(
                                            color: Colors.blue, fontSize: 14),
                                      ),
                                      const SizedBox(
                                        width: 5,
                                      ),
                                    ],
                                  ),
                                  Row(
                                    children: [
                                      Flexible(
                                        child: Text(
                                          '${_athlete[i].lastName} ${_athlete[i].firstName}',
                                          style: const TextStyle(
                                              color: Colors.black,
                                              fontFamily: 'Cera',
                                              fontWeight: FontWeight.bold,
                                              fontSize: 18),
                                        ),
                                      ),
                                    ],
                                  ),
                                  const SizedBox(
                                    height: 5,
                                  ),
                        });
                  } else if (snapshot.hasError) {
                    logger.e('${snapshot.error}');
                  }
                  return const Center(
                    heightFactor: 20,
                    child: CircularProgressIndicator.adaptive(),
                  );
                },
              ),
            ]),
          ),
          Align(
            alignment: Alignment.bottomCenter,
            child: Container(
              width: double.infinity,
              height: 60,
              child: ElevatedButton(
                style: ElevatedButton.styleFrom(
                    disabledBackgroundColor: Colors.grey),
                onPressed: () async {
                        Navigator.of(context).pushNamed(
                            SelectedAthletes.routeName,
                            arguments: selectedAthlete.toList());
                      }),
                child: Column(
                  children: [
                    const Text(
                      'ΝΕΧΤ',
                      style: TextStyle(
                          fontWeight: FontWeight.bold,
                          color: Colors.white,
                          fontSize: 18),
                    ),
                  ],
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

希望有人能帮忙解决这个问题，非常感谢！

内容的提问来源于stack exchange，提问作者kate_3dev