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flutter - 使用 Json 错误是 * type 'List' 不是 'String' 类型的子类型*

问题描述

这是我的回应 http://dummy.restapiexample.com/api/v1/employees

我正在显示来自 api 的列表，我在 response.body 中得到了响应，但随后不知道发生了什么

我的 PODO 或模型是

class NewData {
  String id;
  String employeeName;
  String employeeSalary;
  String employeeAge;
  String profileImage;

  NewData(
      {this.id,
        this.employeeName,
        this.employeeSalary,
        this.employeeAge,
        this.profileImage});

  factory NewData.fromJson(Map<String, dynamic> json) => NewData(
    id: json["id"],
    employeeName: json["employee_name"],
    employeeSalary: json["employee_salary"],
    employeeAge: json["employee_age"],
    profileImage: json["profile_image"],
  );


  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['employee_name'] = this.employeeName;
    data['employee_salary'] = this.employeeSalary;
    data['employee_age'] = this.employeeAge;
    data['profile_image'] = this.profileImage;
    return data;
  }
}

我的 Main.dart 是

body: Container(
        child: Column(
          children: <Widget>[
            FutureBuilder<NewData>(
                future: fetchPost(),
                builder: (context, snapshot) {
                  if (snapshot.connectionState == ConnectionState.done) {
                    if (snapshot.hasError) {
                      return Text("ERROR : - " + snapshot.error.toString());
                    }
                    List<NewData> data = snapshot.data as List<NewData>;
                    return new ListView.builder(
                      itemCount: data.length,
                      itemBuilder: (context, index) {
                        return new ListTile(
                          title: new Text(data[index].employeeName),
                        );
                      },
                    );
                  } else {
                    // By default, show a loading spinner.
                    return Center(
                      child: CircularProgressIndicator(),
                    );
                  }
                }),
          ],
        ),
      ),
    );
  }

  Future<NewData> fetchPost() async {
    var response = await http.get(url);
    if (response.statusCode == 200) {
      // If server returns an OK response, parse the JSON.
      var resp = json.decode(response.body);
      print(resp.toString());
      return NewData.fromJson(resp);
    } else {
      // If that response was not OK, throw an error.
      throw Exception('Failed to load post');
    }
  }

但我收到了这个错误

“列表”类型不是“字符串”类型的子类型

帮我解决这个问题，我如何摆脱它？

标签： flutter

解决方案

您请求的 JSON 返回一个对象列表，并且在您的代码中，您正在解析单个对象。因此，当您解析它时，NewData.fromJson(resp)您会尝试解析对象列表而不是单个对象。

你最好这样做：

Iterable l = json.decode(rseponse.body);
List<NewData> dataList = l.map((Map model)=> NewData.fromJson(model)).toList();

来源：如何在颤动中反序列化来自json的对象列表

然后，您将能够将fetchPost()返回类型更新为Future<List<NewData>>.

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