Flutter异步编程 http网络请求数据

import 'dart:convert';

import 'package:flutter/material.dart';

import 'package:http/http.dart' as http;

import 'dart:async';

class HttpDemo extends StatelessWidget {

  @override

  Widget build(BuildContext context) {

    return Scaffold(

      appBar: AppBar(

        title: Text('HttpDemo'),

        elevation: 0.0,

      ),

      body: HttpDemoHome(),

    );

  }

}

class HttpDemoHome extends StatefulWidget {

  @override

  _HttpDemoHomeState createState() => _HttpDemoHomeState();

}

class _HttpDemoHomeState extends State<HttpDemoHome> {

  @override

  void initState() {

    super.initState();

    // fetchPosts()

    //   .then((value) => print(value));

    // final post = {

    //   'title': 'hello',

    //   'description': 'nice to meet you.',

    // };

    // print(post['title']);

    // print(post['description']);

    // final postJson = json.encode(post);

    // print(postJson);

    // final postJsonConverted = json.decode(postJson);

    // print(postJsonConverted['title']);

    // print(postJsonConverted['description']);

    // print(postJsonConverted is Map);

    // final postModel = Post.fromJson(postJsonConverted);

    // print('title: ${postModel.title}, description: ${postModel.description}');

    // print('${json.encode(postModel)}');

  }

  Future<List<Post>> fetchPosts() async {

    final response =

        await http.get('https://resources.ninghao.net/demo/posts.json');

    // print('statusCode: ${response.statusCode}');

    // print('body: ${response.body}');

    if (response.statusCode == 200) {

      final responseBody = json.decode(response.body);

      List<Post> posts = responseBody['posts']

        .map<Post>((item) => Post.fromJson(item))

        .toList();

      return posts;

    } else {

      throw Exception('Failed to fetch posts.');

    }

  }

  @override

  Widget build(BuildContext context) {

    return FutureBuilder(

      future: fetchPosts(),

      builder: (BuildContext context, AsyncSnapshot snapshot) {

        print('data: ${snapshot.data}');

        print('connectionState: ${snapshot.connectionState}');

        if (snapshot.connectionState == ConnectionState.waiting) {

          return Center(

            child: Text('loading...'),

          );

        }

        return ListView(

          children: snapshot.data.map<Widget>((item) {

            return ListTile(

              title: Text(item.title),

              subtitle: Text(item.author),

              leading: CircleAvatar(

                backgroundImage: NetworkImage(item.imageUrl),

              ),

            );

          }).toList(),

        );

      },

    );

  }

}

class Post {

  final int id;

  final String title;

  final String description;

  final String author;

  final String imageUrl;

  Post(

    this.id,

    this.title,

    this.description,

    this.author,

    this.imageUrl,

  );

  Post.fromJson(Map json)

    : id = json['id'],

      title = json['title'],

      description = json['description'],

      author = json['author'],

      imageUrl = json['imageUrl'];

  Map toJson() => {

    'title': title,

    'descritpion': description,

  };

}

 http: ^0.12.0