Question

在嵌套对象波动中解析复杂的json 我正在尝试从对象内部的对象列表中提取数据试图拉类型和价值假设我要访问视觉效果包含一些字段和一组对象字段。

     "visuals": [{"type": "color", "value": "red"},]

这是我的json文件

  {
    "name": "Lionel Messi",
    "email": "LionelMessi@gmail.com",
    "age": "23",
    "photo": "https://img.bleacherreport.net/img/images/photos/003/738/191/hi-res-bd496f7bef33e47363703d3cce58c50e_crop_north.jpg?h=533&w=800&q=70&crop_x=center&crop_y=top",
    "url": "http://www.john-wesley.com",
    "trainingPlan": {
      "id": "1",
      "creator": "LionelMessi@gmail.com",
      "creationDate": "21/04/20",
      "visuals": [
        {
          "type": "color",
          "value": "red",

        }
      ],
      "transition": {"length": "2", "delay": "1"},
      "duration": {"type": "Countdown", "time": "20"}

    }
  }



]

这很扑朔迷离

import 'dart:convert';

class Record {
  String name;
  String email;
  String age;
  String photo;
  String url;
  final trainingPlan;

  Record({
    this.name,
    this.email,
    this.age,
    this.photo,
    this.url,
    this.trainingPlan,
  });

  factory Record.fromJson(Map<String, dynamic> json) {
    return new Record(
      name: json['name'],
      email: json['email'],
      age: json['age'],
      photo: json['photo'],
      url: json['url'],
      trainingPlan: TrainingPlan.fromJson(json['trainingPlan']),
    );
  }
}

class TrainingPlan {
  final String id;
  final String creator;
  final String creationDate;
  final transition;
  final duration;
  final List<Visuals> visuals;

  TrainingPlan(
      {this.id,
      this.creator,
      this.creationDate,
      this.transition,
      this.duration,
      this.visuals});

  TrainingPlan.fromJson(Map<String, dynamic> json)
      : id = json['id'],
        creator = json['creator'],
        creationDate = json['creationDate'],
        transition = Transition.fromJson(json['transition']),
        duration = Duration.fromJson(json['duration']),
        visuals = parseVisuals(json);

  static List<Visuals> parseVisuals(visualsJson) {
    var list = visualsJson['visuals'] as List;
    List<Visuals> visualsList =
    list.map((data) => Visuals.fromJson(data)).toList();
    return visualsList;
  }
}

class Transition {
  final String length;
  final String delay;

  Transition({
    this.length,
    this.delay,
  });

  Transition.fromJson(Map<String, dynamic> json)
      : length = json['length'],
        delay = json['delay'];
}

class Duration {
  final String type;
  final String time;

  Duration({
    this.type,
    this.time, int seconds,
  });

  Duration.fromJson(Map<String, dynamic> json)
      : type = json['type'],
        time = json['time'];
}

class Visuals {
  final String type;
  final String value;

  Visuals({this.type, this.value});

  factory Visuals.fromJson(Map<String, dynamic> parsedJson) {
    return Visuals(
        type: parsedJson['type'],
        value: parsedJson['value'],
  }
}

在嵌套对象波动中解析复杂的json 我正在尝试从对象内部的对象列表中提取数据试图拉类型和价值假设我要访问视觉效果包含一些字段和一组对象字段。

Answer 1

您可以在下面复制粘贴运行完整代码
您可以在下面查看相关类的完整代码

代码段

Record recordFromJson(String str) => Record.fromJson(json.decode(str));
...
Record record = recordFromJson(jsonString);
print(
    '${record.trainingPlan.visuals[0].type} ${record.trainingPlan.visuals[0].value}');

输出

I/flutter (30092): color red

完整代码

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

Record recordFromJson(String str) => Record.fromJson(json.decode(str));

String recordToJson(Record data) => json.encode(data.toJson());

class Record {
  String name;
  String email;
  String age;
  String photo;
  String url;
  TrainingPlan trainingPlan;

  Record({
    this.name,
    this.email,
    this.age,
    this.photo,
    this.url,
    this.trainingPlan,
  });

  factory Record.fromJson(Map<String, dynamic> json) => Record(
        name: json["name"],
        email: json["email"],
        age: json["age"],
        photo: json["photo"],
        url: json["url"],
        trainingPlan: TrainingPlan.fromJson(json["trainingPlan"]),
      );

  Map<String, dynamic> toJson() => {
        "name": name,
        "email": email,
        "age": age,
        "photo": photo,
        "url": url,
        "trainingPlan": trainingPlan.toJson(),
      };
}

class TrainingPlan {
  String id;
  String creator;
  String creationDate;
  List<Visual> visuals;
  Transition transition;
  Duration duration;

  TrainingPlan({
    this.id,
    this.creator,
    this.creationDate,
    this.visuals,
    this.transition,
    this.duration,
  });

  factory TrainingPlan.fromJson(Map<String, dynamic> json) => TrainingPlan(
        id: json["id"],
        creator: json["creator"],
        creationDate: json["creationDate"],
        visuals:
            List<Visual>.from(json["visuals"].map((x) => Visual.fromJson(x))),
        transition: Transition.fromJson(json["transition"]),
        duration: Duration.fromJson(json["duration"]),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "creator": creator,
        "creationDate": creationDate,
        "visuals": List<dynamic>.from(visuals.map((x) => x.toJson())),
        "transition": transition.toJson(),
        "duration": duration.toJson(),
      };
}

class Duration {
  String type;
  String time;

  Duration({
    this.type,
    this.time,
  });

  factory Duration.fromJson(Map<String, dynamic> json) => Duration(
        type: json["type"],
        time: json["time"],
      );

  Map<String, dynamic> toJson() => {
        "type": type,
        "time": time,
      };
}

class Transition {
  String length;
  String delay;

  Transition({
    this.length,
    this.delay,
  });

  factory Transition.fromJson(Map<String, dynamic> json) => Transition(
        length: json["length"],
        delay: json["delay"],
      );

  Map<String, dynamic> toJson() => {
        "length": length,
        "delay": delay,
      };
}

class Visual {
  String type;
  String value;

  Visual({
    this.type,
    this.value,
  });

  factory Visual.fromJson(Map<String, dynamic> json) => Visual(
        type: json["type"],
        value: json["value"],
      );

  Map<String, dynamic> toJson() => {
        "type": type,
        "value": value,
      };
}

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;

  void _incrementCounter() {
    String jsonString = '''
    {
    "name": "Lionel Messi",
    "email": "LionelMessi@gmail.com",
    "age": "23",
    "photo": "https://img.bleacherreport.net/img/images/photos/003/738/191/hi-res-bd496f7bef33e47363703d3cce58c50e_crop_north.jpg?h=533&w=800&q=70&crop_x=center&crop_y=top",
    "url": "http://www.john-wesley.com",
    "trainingPlan": {
      "id": "1",
      "creator": "LionelMessi@gmail.com",
      "creationDate": "21/04/20",
      "visuals": [
        {
          "type": "color",
          "value": "red"
        }
      ],
      "transition": {"length": "2", "delay": "1"},
      "duration": {"type": "Countdown", "time": "20"}
    }
}
    ''';

    Record record = recordFromJson(jsonString);
    print(
        '${record.trainingPlan.visuals[0].type} ${record.trainingPlan.visuals[0].value}');

    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

在嵌套对象抖动中解析复杂的json

1 个答案: