Question

我正在设计一个带有List-List-Detail视图的应用程序（列表概览，每个列表，每个列表中所选项目的详细信息），从静态JSON文件中提取所有数据。

我想知道读取，解析和显示JSON文件的最佳结构是什么。我应该为每个视图设计模型：所有列表，每个列表和每个项目的概述，并将它们作为单独的文件？是否所有资产加载和JSON解析都发生在这些模型文件中？每个视图是否只接受PODO形式的解析数据？

我一直按照here的说明进行整体设计，但我仍然坚持使用JSON文件的最佳方法，因为他们在Widget设计中添加了异步元素。

Answer 1

是的，您需要创建Model类来处理JSON响应，

您可以使用相同的模型类来列出列表，但不要忘记将子列表项添加到同一模型中

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');

  // Use the compute function to run parsePhotos in a separate isolate
  return compute(parsePhotos, response.body);
}

// A function that will convert a response body into a List<Photo>
List<Photo> parsePhotos(String responseBody) {
  final parsed = json.decode(responseBody).cast<Map<String, dynamic>>();

  return parsed.map<Photo>((json) => new 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 new 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,
      home: new MyHomePage(title: appTitle),
    );
  }
}

class MyHomePage extends StatelessWidget {
  final String title;

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

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(title),
      ),
      body: new FutureBuilder<List<Photo>>(
        future: fetchPhotos(new http.Client()),
        builder: (context, snapshot) {
          if (snapshot.hasError) print(snapshot.error);

          return snapshot.hasData
              ? new PhotosList(photos: snapshot.data)
              : new Center(child: new CircularProgressIndicator());
        },
      ),
    );
  }
}

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

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

  @override
  Widget build(BuildContext context) {
    return new GridView.builder(
      gridDelegate: new SliverGridDelegateWithFixedCrossAxisCount(
        crossAxisCount: 2,
      ),
      itemCount: photos.length,
      itemBuilder: (context, index) {
        return new Image.network(photos[index].thumbnailUrl);
      },
    );
  }
}

带有JSON

1 个答案: