flutter处理json

现在的APP几乎没有单机版的，大部分APP都需要联网。现在采用的主流的前后端交互方式是json，flutter在处理json方面也提供了相应的方案。
新建一个flutter应用，然后在pubspec.yaml添加依赖

dependencies:
  flutter:
    sdk: flutter
  json_annotation: ^2.0.0

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.2

dev_dependencies:
  flutter_test:
    sdk: flutter
  build_runner: ^1.0.0
  json_serializable: ^2.0.0
  build_verify: ^1.0.0

废话不多说，贴代码

import 'package:json_annotation/json_annotation.dart';

part 'User.g.dart';

@JsonSerializable()
class User {
  final int code;
  final String status;
  final String msg;
  @JsonKey(nullable: false)
  List<Item> data;

  User(this.code, this.status, this.msg, {List<Item> data})
      : data = data ?? <Item>[];

  factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);

  Map<String, dynamic> toJson() => _$UserToJson(this);
}

@JsonSerializable(includeIfNull: false)
class Item {
  String title;
  List<UserDetail> data;

  Item();

  factory Item.fromJson(Map<String, dynamic> json) => _$ItemFromJson(json);

  Map<String, dynamic> toJson() => _$UserToJson(this);
}

@JsonSerializable()
class UserDetail {
  int id;
  String name;

  UserDetail();

  factory UserDetail.fromJson(Map<String, dynamic> json) =>
      _$UserDetailFromJson(json);

  Map<String, dynamic> toJson() => _$UserDetailToJson(this);
}

@JsonLiteral('user.json')
Map get glossaryData => _$glossaryDataJsonLiteral;

首先，我们根据json串生成响应的model
其次，执行flutter packages pub run build_runner build 生成需要的文件

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or press Run > Flutter Hot Reload in IntelliJ). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: new _MyAppWidget(),
    );
  }
}

class _MyAppWidget extends StatefulWidget {
  @override
  State createState() {
    return new _MyAppState();
  }
}

class _MyAppState extends State<_MyAppWidget> {
  String jsonStr;
  var userData;

  void _loadJson() async {
    rootBundle.loadString('assets/data/user.json').then((val) {
      var user = json.decode(val);
      setState(() {
        userData = user['data'];
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(),
      body: new Center(
        child: new Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            new IconButton(
              icon: new Icon(Icons.refresh),
              onPressed: () {
                _loadJson();
                if (jsonStr != null) {
                  var user = json.decode(jsonStr);
                  print(user['data']);
                }
              },
            ),
            new Expanded(
              child: userData == null
                  ? new Text("$jsonStr")
                  : new ListView.builder(
                      itemBuilder: (context, index) {
                        return new Column(
                          children: <Widget>[
                            new ListTile(
                              title: new Text('${userData[index]['title']}'),
                            ),
                          ],
                        );
                      },
                      itemCount: userData.length,
                    ),
            ),
          ],
        ),
      ),
    );
  }
}

参考文章
json处理

json处理，适合大项目

老规矩github上代码