颤振：如何将Json文件下载到本地然后访问它

目前，我正在通过

DefaultAssetBundle

访问一个特定的JSON文件

country.JSON

，如下所示：

Future<List<Country>> getCountryFromJson(BuildContext context) async {
    String jsonString =
        await DefaultAssetBundle.of(context).loadString('assets/country.json');
    List<dynamic> raw = jsonDecode(jsonString);
    return raw.map((e) => Country.fromJson(e)).toList();
  }

import 'dart:convert';
import 'dart:core';
import 'package:ask/country.dart';
import 'package:flutter/material.dart';


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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  Future<List<Country>> getCountryFromJson(BuildContext context) async {
    String jsonString =
        await DefaultAssetBundle.of(context).loadString('assets/country.json');
    List<dynamic> raw = jsonDecode(jsonString);
    return raw.map((e) => Country.fromJson(e)).toList();
  }

  Widget build(BuildContext context) {
    return new MaterialApp(
        home: Scaffold(
            appBar: AppBar(title: Text('Country')),
            body: Container(
                child: FutureBuilder(
                    future: getCountryFromJson(context),
                    builder: (context, data) {
                      if (data.hasData) {
                        List<Country> countries = data.data;
                        return ListView.builder(
                            itemCount: countries.length,
                            itemBuilder: (context, index) {
                              return Padding(
                                  padding: const EdgeInsets.all(5.0),
                                  child: Column(children: <Widget>[
                                    Text(
                                      countries[index].country,
                                    )
                                  ]));
                            });
                      } else {
                        return Center(child: CircularProgressIndicator());
                      }
                    }))));
  }
}