有人能帮我实现默认颤动计数器应用的Sqflite吗？

dependencies:
  sqflite: ^x.x.x

import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart';

class DatabaseHelper {
  static final DatabaseHelper _instance = DatabaseHelper.internal();
  factory DatabaseHelper() => _instance;

  static Database? _db;

  Future<Database?> get db async {
    if (_db != null) {
      return _db;
    }
    _db = await initDb();
    return _db;
  }

  DatabaseHelper.internal();

  Future<Database> initDb() async {
    String databasesPath = await getDatabasesPath();
    String path = join(databasesPath, 'counter.db');

    // 打开数据库
    return await openDatabase(path, version: 1, onCreate: _onCreate);
  }

  void _onCreate(Database db, int version) async {
    // 创建表
    await db.execute('''
      CREATE TABLE counter (
        id INTEGER PRIMARY KEY,
        count INTEGER
      )
    ''');

    // 插入默认数据
    await db.rawInsert('INSERT INTO counter (id, count) VALUES(1, 0)');
  }

  // 更新计数器
  Future<void> updateCounter(int count) async {
    Database? dbClient = await db;
    await dbClient?.update('counter', {'count': count}, where: 'id = ?', whereArgs: [1]);
  }

  // 获取计数器
  Future<int> getCounter() async {
    Database? dbClient = await db;
    List<Map<String, dynamic>> result = await dbClient?.query('counter', where: 'id = ?', whereArgs: [1]);
    return result.isNotEmpty ? result.first['count'] : 0;
  }
}

import 'package:flutter/material.dart';

class CounterPage extends StatefulWidget {
  @override
  _CounterPageState createState() => _CounterPageState();
}

class _CounterPageState extends State<CounterPage> {
  int _counter = 0;
  DatabaseHelper _databaseHelper = DatabaseHelper();

  @override
  void initState() {
    super.initState();
    _loadCounter();
  }

  void _loadCounter() async {
    int counter = await _databaseHelper.getCounter();
    setState(() {
      _counter = counter;
    });
  }

  void _incrementCounter() async {
    setState(() {
      _counter++;
    });
    await _databaseHelper.updateCounter(_counter);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Counter App'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              '$_counter',
              style: TextStyle(fontSize: 24),
            ),
            SizedBox(height: 16),
            ElevatedButton(
              onPressed: _incrementCounter,
              child: Text('Increment'),
            ),
          ],
        ),
      ),
    );
  }
}

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: CounterPage(),
    );
  }
}