Flutter API数据解析问题：无法获取Items类中的Address列表

我正在练习Flutter的Fetch API，目前能获取部分数据，但Items类里的Address列表信息无法正常解析，不确定当前实现是否正确，求帮忙排查。

获取数据的代码 #

List<Items> _list = [];
List<Items> _search = [];
var loading = false;
Future fetchMos() async {
  setState(() {
    loading = true;
  });
  _list.clear();
  var client = http.Client();
  String mosUrl = '';
  var url = Uri.parse(mosUrl);
  var headers = {'Client-Token': ''};
  var response = await client.get(url, headers: headers);
  if (response.statusCode == 200) {
    var data = jsonDecode((utf8.decode(response.bodyBytes)))['items'];
    setState(() {
      for (Map i in data) {
        _list.add(Items.fromJson(i));
        loading = false;
      }
    });
  }
}

数据模型类代码 #

class Items {
  String? custnum;
  String? name;
  List<Address>? address;
  Items({this.custnum, this.name, this.address});

  Items.fromJson(json) {
    custnum = json['custnum'];
    name = json['name'];
    if (json['address'] != null) {
      address = <Address>[];
      json['address'].forEach((v) {
        address!.add(new Address.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['custnum'] = this.custnum;
    data['name'] = this.name;
    if (this.address != null) {
      data['address'] = this.address!.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class Address {
  int? shipto;
  String? addr1;
  String? thanon;
  String? tambon;
  String? amphur;
  String? provCode;
  String? province;
  String? country;
  String? phone;
  String? email;
  String? postcode;
  String? contact;
  String? latitude;
  String? longitude;
  String? fax;
  String? soi;
  String? zipcode;

  Address({
    this.shipto,
    this.addr1,
    this.thanon,
    this.tambon,
    this.amphur,
    this.provCode,
    this.province,
    this.zipcode,
    this.country,
    this.phone,
    this.email,
    this.postcode,
    this.contact,
    this.latitude,
    this.longitude,
    this.fax,
    this.soi
  });

  Address.fromJson(json) {
    shipto = json['shipto'];
    addr1 = json['addr1'];
    thanon = json['thanon'];
    tambon = json['tambon'];
    amphur = json['amphur'];
    provCode = json['prov_code'];
    province = json['province'];
    zipcode = json['zipcode'];
    country = json['country'];
    phone = json['phone'];
    email = json['email'];
    postcode = json['postcode'];
    contact = json['contact'];
    latitude = json['latitude'];
    longitude = json['longitude'];
    fax = json['fax'];
    soi = json['soi'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['shipto'] = this.shipto;
    data['addr1'] = this.addr1;
    data['thanon'] = this.thanon;
    data['tambon'] = this.tambon;
    data['amphur'] = this.amphur;
    data['prov_code'] = this.provCode;
    data['province'] = this.province;
    data['zipcode'] = this.zipcode;
    data['phone'] = this.phone;
    data['email'] = this.email;
    data['postcode'] = this.postcode;
    data['contact'] = this.contact;
    data['longitude'] = this.longitude;
    data['fax'] = this.fax;
    data['soi'] = this.soi;
    return data;
  }
}

排查关键点 #

• 模型字段遗漏：Address类的toJson方法缺失latitude字段，会导致数据序列化/反序列化不一致，需添加data['latitude'] = this.latitude;。
• 空安全风险：Items.fromJson中直接使用address!.add，若address初始化异常会触发空指针，建议用if (address != null)包裹操作。
• loading状态错误：循环内重复设置loading = false，应将该语句移到循环外，确保所有数据加载完成后再更新状态。
• 类型转换不严谨：for (Map i in data)中data为动态类型，建议先转为List<Map<String, dynamic>>避免类型错误：

  List<Map<String, dynamic>> itemsList = List.castFrom(data);
  for (var i in itemsList) {
    _list.add(Items.fromJson(i));
  }
  

• API字段匹配：确认API返回的address是数组类型，且内部字段名与模型完全匹配（比如prov_code对应provCode是否正确）。

内容的提问来源于stack exchange，提问作者Ppnncs