在Flutter中使用SharedPreferences和Provider的正确方式是什么？

dependencies:
  shared_preferences: ^2.0.8
  provider: ^6.0.1

import 'package:shared_preferences/shared_preferences.dart';

SharedPreferences prefs = await SharedPreferences.getInstance();

// 读取数据
String? username = prefs.getString('username');

// 写入数据
await prefs.setString('username', 'John Doe');

import 'package:provider/provider.dart';

ChangeNotifierProvider(
  create: (context) => MyDataModel(),
  child: MyApp(),
);

MyDataModel dataModel = Provider.of<MyDataModel>(context);

import 'package:shared_preferences/shared_preferences.dart';
import 'package:provider/provider.dart';

class MyDataModel extends ChangeNotifier {
  SharedPreferences _prefs;

  MyDataModel() {
    _initSharedPreferences();
  }

  Future<void> _initSharedPreferences() async {
    _prefs = await SharedPreferences.getInstance();
  }

  String? getUsername() {
    return _prefs.getString('username');
  }

  Future<void> setUsername(String username) async {
    await _prefs.setString('username', username);
    notifyListeners();
  }
}

MyDataModel dataModel = Provider.of<MyDataModel>(context);
String? username = dataModel.getUsername();