如何在Flutter中将Provider的数据设置为存储在SharedPreferences中的数据？

dependencies:
  shared_preferences: ^2.0.8

import 'package:shared_preferences/shared_preferences.dart';

class SharedPreferencesService {
  static const String counterKey = 'counter';

  Future<int> getCounter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return prefs.getInt(counterKey) ?? 0;
  }

  Future<void> setCounter(int value) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    await prefs.setInt(counterKey, value);
  }
}

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

class CounterModel extends ChangeNotifier {
  int _counter;
  SharedPreferencesService _sharedPreferencesService;

  CounterModel() {
    _counter = 0;
    _sharedPreferencesService = SharedPreferencesService();
    _loadCounter();
  }

  int get counter => _counter;

  void incrementCounter() {
    _counter++;
    _saveCounter();
    notifyListeners();
  }

  void _loadCounter() async {
    _counter = await _sharedPreferencesService.getCounter();
    notifyListeners();
  }

  void _saveCounter() async {
    await _sharedPreferencesService.setCounter(_counter);
  }
}

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

void main() {
  runApp(
    ChangeNotifierProvider(
      create: (context) => CounterModel(),
      child: MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Provider with SharedPreferences',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final counterModel = Provider.of<CounterModel>(context);
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Provider with SharedPreferences'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'Counter Value:',
            ),
            Text(
              '${counterModel.counter}',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          counterModel.incrementCounter();
        },
        child: Icon(Icons.add),
      ),
    );
  }
}