Flutter:如何使用存储在SQFlite中的数据？

dependencies:
  flutter:
    sdk: flutter
  sqflite: ^2.0.0+4

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

class DatabaseHelper {
  static final DatabaseHelper _instance = new DatabaseHelper._internal();
  factory DatabaseHelper() => _instance;
  static Database? _database;

  DatabaseHelper._internal();

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

  Future<Database> _initDatabase() async {
    return await openDatabase(
      'my_database.db',
      version: 1,
      onOpen: (db) {},
      onCreate: (Database db, int version) async {
        await db.execute(
          'CREATE TABLE users(id INTEGER PRIMARY KEY, name TEXT, email TEXT)',
        );
      },
    );
  }
}

Future<void> insertUser(User user) async {
  final db = await DatabaseHelper().database;
  await db.insert(
    'users',
    user.toMap(),
    conflictAlgorithm: ConflictAlgorithm.replace,
  );
}

Future<List<User>> getUsers() async {
  final db = await DatabaseHelper().database;
  final List<Map<String, dynamic>> maps = await db.query('users');
  return List.generate(maps.length, (i) {
    return User.fromMap(maps[i]);
  });
}