Flutter with provider pattern:如何以及从何处获取异步数据

Future<String> fetchData() async {
  // 异步获取数据的逻辑
  return "异步数据";
}

void main() async {
  String data = await fetchData();
  print(data);
}

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

void fetchData() async {
  var response = await http.get(Uri.parse('https://example.com/api/data'));
  if (response.statusCode == 200) {
    var data = response.body;
    print(data);
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

class DataProvider with ChangeNotifier {
  String _data = '';

  String get data => _data;

  Future<void> fetchData() async {
    // 异步获取数据的逻辑
    _data = await fetchDataFromServer();
    notifyListeners();
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) => DataProvider(),
      child: MaterialApp(
        home: Scaffold(
          appBar: AppBar(
            title: Text('Flutter with Provider Pattern'),
          ),
          body: Consumer<DataProvider>(
            builder: (context, provider, _) {
              if (provider.data.isEmpty) {
                return Center(
                  child: CircularProgressIndicator(),
                );
              } else {
                return Text(provider.data);
              }
            },
          ),
          floatingActionButton: FloatingActionButton(
            onPressed: () {
              Provider.of<DataProvider>(context, listen: false).fetchData();
            },
            child: Icon(Icons.refresh),
          ),
        ),
      ),
    );
  }
}

void main() {
  runApp(MyApp());
}