Как добавить объекты в список во флаттере

Question

Мой API возвращает данные в следующем формате, как мне использовать данные, возвращаемые API?

{
    "result": {
        "circles": [
            {
                "_id": "5f03b28e81518d0017f250bf",
                "name": "reflex",
                "description": "reflex is not bad at the same 6time and then ",
                "moderators": [],
                "__v": 0
            },
            {
                "_id": "5f03b32881518d0017f250c0",
                "name": "dej ivo IDF",
                "description": "talk ugh to be honest with my friends ",
                "moderators": [],
                "__v": 0
            },
        ]
    }
}

Answer 1

Вы можете скопировать и вставить полный код ниже
Вы можете выполнить синтаксический анализ с помощью payloadFromJson, вы можете увидеть соответствующее определение класса Payload в полном коде
и отобразить с помощью FutureBuilder
фрагмента кода

Payload payloadFromJson(String str) => Payload.fromJson(json.decode(str));
...
FutureBuilder(
        future: _future,
        builder: (context, AsyncSnapshot<Payload> snapshot) {
          switch (snapshot.connectionState) {
            case ConnectionState.none:
              return Text('none');
            case ConnectionState.waiting:
              return Center(child: CircularProgressIndicator());
            case ConnectionState.active:
              return Text('');
            case ConnectionState.done:
              if (snapshot.hasError) {
                return Text(
                  '${snapshot.error}',
                  style: TextStyle(color: Colors.red),
                );
              } else {
                return ListView.builder(
                    itemCount: snapshot.data.result.circles.length,

рабочая демонстрация

введите описание изображения здесь

полный код

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

Payload payloadFromJson(String str) => Payload.fromJson(json.decode(str));

String payloadToJson(Payload data) => json.encode(data.toJson());

class Payload {
  Payload({
    this.result,
  });

  Result result;

  factory Payload.fromJson(Map<String, dynamic> json) => Payload(
        result: Result.fromJson(json["result"]),
      );

  Map<String, dynamic> toJson() => {
        "result": result.toJson(),
      };
}

class Result {
  Result({
    this.circles,
  });

  List<Circle> circles;

  factory Result.fromJson(Map<String, dynamic> json) => Result(
        circles:
            List<Circle>.from(json["circles"].map((x) => Circle.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "circles": List<dynamic>.from(circles.map((x) => x.toJson())),
      };
}

class Circle {
  Circle({
    this.id,
    this.name,
    this.description,
    this.moderators,
    this.v,
  });

  String id;
  String name;
  String description;
  List<dynamic> moderators;
  int v;

  factory Circle.fromJson(Map<String, dynamic> json) => Circle(
        id: json["_id"],
        name: json["name"],
        description: json["description"],
        moderators: List<dynamic>.from(json["moderators"].map((x) => x)),
        v: json["__v"],
      );

  Map<String, dynamic> toJson() => {
        "_id": id,
        "name": name,
        "description": description,
        "moderators": List<dynamic>.from(moderators.map((x) => x)),
        "__v": v,
      };
}

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  Future<Payload> _future;

  Future<Payload> _getRecords() async {
    String jsonString = '''
    {
    "result": {
        "circles": [
            {
                "_id": "5f03b28e81518d0017f250bf",
                "name": "reflex",
                "description": "reflex is not bad at the same 6time and then ",
                "moderators": [],
                "__v": 0
            },
            {
                "_id": "5f03b32881518d0017f250c0",
                "name": "dej ivo IDF",
                "description": "talk ugh to be honest with my friends ",
                "moderators": [],
                "__v": 0
            }
        ]
    }
}
    ''';

    var response = http.Response(jsonString, 200);

    if (response.statusCode == 200) {
      return payloadFromJson(jsonString);
    } else {
      print(response.statusCode);
    }
  }

  @override
  void initState() {
    _future = _getRecords();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: FutureBuilder(
            future: _future,
            builder: (context, AsyncSnapshot<Payload> snapshot) {
              switch (snapshot.connectionState) {
                case ConnectionState.none:
                  return Text('none');
                case ConnectionState.waiting:
                  return Center(child: CircularProgressIndicator());
                case ConnectionState.active:
                  return Text('');
                case ConnectionState.done:
                  if (snapshot.hasError) {
                    return Text(
                      '${snapshot.error}',
                      style: TextStyle(color: Colors.red),
                    );
                  } else {
                    return ListView.builder(
                        itemCount: snapshot.data.result.circles.length,
                        itemBuilder: (context, index) {
                          return Card(
                              elevation: 6.0,
                              child: Padding(
                                padding: const EdgeInsets.only(
                                    top: 6.0,
                                    bottom: 6.0,
                                    left: 8.0,
                                    right: 8.0),
                                child: Row(
                                  crossAxisAlignment: CrossAxisAlignment.start,
                                  children: <Widget>[
                                    Text(snapshot
                                        .data.result.circles[index].name),
                                    Spacer(),
                                    Text(snapshot.data.result.circles[index]
                                        .description),
                                  ],
                                ),
                              ));
                        });
                  }
              }
            }));
  }
}

Answer 2

Проверьте документы по JSON сериализации .

Предполагая, что JSON находится в строковом формате, это преобразует его в карту dart: Map<String, dynamic> data = jsonDecode(yourJsonString)