在Flutter中使用SQFLite进行用户凭据检查的步骤如下:
pubspec.yaml
文件中添加以下依赖项:dependencies:
sqflite: ^2.0.0+3
path: ^2.0.0
然后运行flutter pub get
命令以获取依赖项。
database_helper.dart
的文件,并添加以下代码:import 'dart:async';
import 'package:path/path.dart';
import 'package:sqflite/sqflite.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, 'my_app.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 users (
id INTEGER PRIMARY KEY,
username TEXT,
password TEXT
)
''');
// 插入示例用户
await db.rawInsert('''
INSERT INTO users (id, username, password)
VALUES (1, 'admin', 'password')
''');
}
Future<bool> checkCredentials(String username, String password) async {
Database? dbClient = await db;
var result = await dbClient!.query(
'users',
where: 'username = ? AND password = ?',
whereArgs: [username, password],
);
return result.isNotEmpty;
}
}
DatabaseHelper
类来检查用户凭据。可以创建一个名为login_page.dart
的文件,并添加以下代码:import 'package:flutter/material.dart';
import 'package:your_app/database_helper.dart';
class LoginPage extends StatelessWidget {
final TextEditingController _usernameController = TextEditingController();
final TextEditingController _passwordController = TextEditingController();
void _login(BuildContext context) async {
String username = _usernameController.text;
String password = _passwordController.text;
bool isValid = await DatabaseHelper().checkCredentials(username, password);
if (isValid) {
// 登录成功,导航到下一个页面
Navigator.pushNamed(context, '/home');
} else {
// 显示错误消息
showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: Text('登录失败'),
content: Text('无效的用户名或密码'),
actions: <Widget>[
TextButton(
child: Text('关闭'),
onPressed: () {
Navigator.of(context).pop();
},
),
],
);
},
);
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('登录'),
),
body: Padding(
padding: EdgeInsets.all(16.0),
child: Column(
children: <Widget>[
TextField(
controller: _usernameController,
decoration: InputDecoration(
labelText: '用户名',
),
),
TextField(
controller: _passwordController,
decoration: InputDecoration(
labelText: '密码',
),
obscureText: true,
),
SizedBox(height: 16.0),
ElevatedButton(
child: Text('登录'),
onPressed: () => _login(context),
),
],
),
),
);
}
}
main.dart
文件中设置路由和启动应用程序。可以添加以下代码:import 'package:flutter/material.dart';
import 'package:your_app/login_page.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'My App',
theme: ThemeData(
primarySwatch: Colors.blue,
),
initialRoute: '/',
routes: {
'/': (context) => LoginPage(),
'/home': (context) => HomePage(),
},
);
}
}
class HomePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Home'),
),
body: Center(
child: Text('Welcome!'),
),
);
}
}
现在,当用户在登录页面中输入用户名和密码并点击登录按钮时,应用程序将使用SQFLite检查用户凭据。如果凭据有效,则导航到主页,否则显示错误消息。
请注意,上述代码示例中的your_app
应替换为您的实际应用程序名称。
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