pubspec.yaml配置http的SDK

cupertino_icons: ^1.0.8
http: ^1.2.2

请求数据的格式转换

// Map 转 json
final chat = {
  'name': '张三',
  'message': '吃饭了吗',
};
final chatJson = json.encode(chat);
print(chatJson);

// json转Map
final newChat = json.decode(chatJson);
print(newChat);

发送请求

import 'dart:convert'; // json依赖
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http; // http请求依赖

class Chat {
  final String? name;
  final String? message;
  final String? imageUrl;
  Chat({this.name, this.message, this.imageUrl});
  //
  factory Chat.formMap(Map map) {
    return Chat(
      name: map['name'],
      message: map['message'],
      imageUrl: map['imageUrl'],
    );
  }
}

class ChatPage extends StatefulWidget {
  @override
  State<ChatPage> createState() => _ChatPageState();
}
class _ChatPageState extends State<ChatPage> {
  @override
  void initState() {
    super.initState();
    getDatas().then((value) {
    
    }).catchError((onError) {
      
    }).whenComplete(() {
      print('数据加载完毕');
    }).timeout(Duration(seconds: 1)).catchError((err) {
      print('超时时长1秒，提示请求超时');
    });
  }
}

// async：异步的请求，不用卡在这等待
Future<List> getDatas() async {
  final url =
      Uri.parse('http://rap2api.taobao.org/app/mock/321326/api/chat/list');
  final res = await http.get(url);
  if (res.statusCode == 200) {
    // 获取相应数据，转成Map类型
    final resBody = json.decode(res.body);
    // map遍历chat_list，把每一项item转成模型数据，最后转成List
    List chatList =
        resBody['chat_list'].map((item) => Chat.formMap(item)).toList();
    return chatList;
  } else {
    throw Exception('statusCode:${res.statusCode}');
  }
}

FutureBuilder 发送的请求

return Scaffold(
  body: Container(
  child: FutureBuilder(
      future: getDatas(),
      builder: (BuildContext context, AsyncSnapshot snapshot) {
        print('data:${snapshot.data}');
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const Center(
            child: Text('Loading...'),
          );
        }
        return ListView(
          children: snapshot.data.map<Widget>((item) {
            return ListTile(
                title: Text(item.name),
                subtitle: Container(
                  alignment: Alignment.bottomCenter,
                  height: 25,
                  child: Text(
                    item.message,
                    overflow: TextOverflow.ellipsis,
                  ),
                ),
                leading: Container(
                  width: 44,
                  height: 44,
                  decoration: BoxDecoration(
                      borderRadius: BorderRadius.circular(6.0),
                      image: DecorationImage(
                          image: NetworkImage(item.imageUrl))),
                ));
          }).toList(),
        );
      }),
  )
);

声明变量接收接口数据，在页面中使用该变量去渲染页面的方式

class _ChatPageState extends State<ChatPage> {
  List _datas = [];

  @override
  void initState() {
    super.initState();
    getDatas().then((value) {
      setState(() {
        _datas = value;
      });
    }).catchError((onError) {
    
	});
  }
}

body: Container(
  child: Container(
    child: _datas.length == 0 ? Center(child: Text('Loading...')) : 
    ListView.builder(
      itemCount: _datas.length,
      itemBuilder: (BuildContext context, int index) {
        return ListTile(
            title: Text(_datas[index].name),
            subtitle: Container(
              alignment: Alignment.bottomCenter,
              height: 25,
              child: Text(
                _datas[index].message,
                overflow: TextOverflow.ellipsis,
              ),
            ),
            leading: Container(
              width: 44,
              height: 44,
              decoration: BoxDecoration(
                borderRadius: BorderRadius.circular(6.0),
                image: DecorationImage(image: NetworkImage(_datas[index].imageUrl))
              ),
            )
        );
      },
    )
  )
)