如何在sqflite flutter中创建表后添加更多列

dependencies:
  sqflite: ^2.0.0+3
  path_provider: ^2.0.2

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

class DatabaseHelper {
  static final DatabaseHelper instance = DatabaseHelper._();
  static Database? _database;

  DatabaseHelper._();

  Future<Database> get database async {
    if (_database != null) return _database!;
    _database = await _initDatabase();
    return _database!;
  }

  Future<Database> _initDatabase() async {
    String path = join(await getDatabasesPath(), 'my_database.db');
    return await openDatabase(
      path,
      version: 1,
      onCreate: _createTables,
      onUpgrade: _upgradeTables,
    );
  }

  Future<void> _createTables(Database db, int version) async {
    await db.execute('''
      CREATE TABLE my_table (
        id INTEGER PRIMARY KEY,
        column1 TEXT,
        column2 INTEGER
      )
    ''');
  }

  Future<void> _upgradeTables(Database db, int oldVersion, int newVersion) async {
    if (oldVersion < 2) {
      await db.execute('ALTER TABLE my_table ADD COLUMN column3 TEXT');
    }
    // Add more upgrade logic for other versions if needed
  }
}

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

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await DatabaseHelper.instance.database; // 初始化数据库
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter SQFlite Demo',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter SQFlite Demo'),
        ),
        body: Center(
          child: ElevatedButton(
            child: Text('Add Column'),
            onPressed: () async {
              Database db = await DatabaseHelper.instance.database;
              await db.execute('ALTER TABLE my_table ADD COLUMN column4 INTEGER');
            },
          ),
        ),
      ),
    );
  }
}