json - 当响应是对象数组时，如何在抖动中解析JSON

Question

我收到以下类型的API响应

[
    {"name":"lakshay","id":"1217","type":"Staff","temperature":56.6,"date":"12-06-2020"},
    {"name":"lakshay","id":"1217","type":"Staff","temperature":56.6,"date":"12-06-2020"},
     .....
]

我需要将整个内容解析为对象列表，以便可以执行类似的操作

// conceptual //
array.map((obj)=>{
  // computation //
})

我从here那里获得了帮助，但是它没有告诉我们如何解析外部数组。

谢谢你的时间。

Answer 1

您可以在下面复制粘贴运行完整代码
第1步:使用List<Payload> payloadList = payloadFromJson(jsonString);进行解析，您可以看到完整的代码以获取详细的Payload类定义
步骤2:进行这样的循环

payloadList.forEach((element) {
      print(element.name);
      print(element.id);
    });

输出

I/flutter (17660): lakshay
I/flutter (17660): 1217
I/flutter (17660): lakshay
I/flutter (17660): 1217

完整的代码

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

List<Payload> payloadFromJson(String str) =>
    List<Payload>.from(json.decode(str).map((x) => Payload.fromJson(x)));

String payloadToJson(List<Payload> data) =>
    json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class Payload {
  Payload({
    this.name,
    this.id,
    this.type,
    this.temperature,
    this.date,
  });

  String name;
  String id;
  String type;
  double temperature;
  String date;

  factory Payload.fromJson(Map<String, dynamic> json) => Payload(
        name: json["name"],
        id: json["id"],
        type: json["type"],
        temperature: json["temperature"].toDouble(),
        date: json["date"],
      );

  Map<String, dynamic> toJson() => {
        "name": name,
        "id": id,
        "type": type,
        "temperature": temperature,
        "date": date,
      };
}

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;
  String jsonString = '''
  [
    {"name":"lakshay","id":"1217","type":"Staff","temperature":56.6,"date":"12-06-2020"},
    {"name":"lakshay","id":"1217","type":"Staff","temperature":56.6,"date":"12-06-2020"}

]
''';

  void _incrementCounter() {
    List<Payload> payloadList = payloadFromJson(jsonString);
    payloadList.forEach((element) {
      print(element.name);
      print(element.id);
    });

    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),
      ),
    );
  }
}