flutter网络请求和详情页展示的例子

总结demo，主要操作如下：

1.使用http 包进行网络请求

2.转换json数据为List<Photo>

3.使用GridView显示缩略图片

4.为缩略图添加onTap，第二屏查看大图

import 'dart:async';
import 'dart:convert';

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

Future<List<Photo>> fetchPhotos(http.Client client) async {
  final response = 
      await client.get('https://jsonplaceholder.typicode.com/photos');
  return compute(parsePhotos, response.body);
}

List<Photo> parsePhotos(String responseBody) {
  final parsed = json.decode(responseBody).cast<Map<String, dynamic>>();
  return parsed.map<Photo>((json) => Photo.fromJson(json)).toList();
}

class Photo {
  final int albumId;
  final int id;
  final String title;
  final String url;
  final String thumbnailUrl;

  Photo({this.albumId, this.id, this.title, this.url, this.thumbnailUrl});

  factory Photo.fromJson(Map<String, dynamic> json) {
    return Photo(
      albumId: json['albumId'] as int,
      id: json['id'] as int,
      title: json['title'] as String,
      url: json['url'] as String,
      thumbnailUrl: json['thumbnailUrl'] as String
    );
  }
}

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final appTitle = 'Isolate Demo';
    return new MaterialApp(
      title: appTitle,
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: appTitle)
    );
  }
}

class MyHomePage extends StatelessWidget {
  final String title;

  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: FutureBuilder<List<Photo>>(
        future: fetchPhotos(http.Client()),
        builder: (context, snapshot) {
          if (snapshot.hasError) print(snapshot.error);
          return snapshot.hasData
                ? PhotosList(photos: snapshot.data)
                : Center(child: CircularProgressIndicator());
        },
      ),
    );
  }
}

class PhotosList extends StatelessWidget {
  final List<Photo> photos;

  PhotosList({Key key, this.photos}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return GridView.builder(
      gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
        crossAxisCount: 2
      ),
      itemCount: photos.length,
      itemBuilder: (context, index) {
        return GestureDetector(
          onTap: () {
            Navigator.push(context, MaterialPageRoute(
              builder: (context) => DetailPage(photo: photos[index]),
            ));
          },
          child: Image.network(photos[index].thumbnailUrl)
        );
      }
    );
  }
}

class DetailPage extends StatelessWidget {

  final Photo photo;

  DetailPage({Key key, this.photo}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(photo.title),
      ),
      body: Center(
        child: Image.network(photo.url),
      ),
    );
  }

}

效果如下：