import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: LoginPage(),
    );
  }
}

class LoginPage extends StatelessWidget {
  final TextEditingController usernameController = TextEditingController();
  final TextEditingController passwordController = TextEditingController();

  void login(BuildContext context) {
    String username = usernameController.text.trim();
    String password = passwordController.text.trim();

    if (username.isEmpty || password.isEmpty) {
      // Show error message if username or password is empty
      showDialog(
        context: context,
        builder: (BuildContext context) {
          return AlertDialog(
            title: Text('Error'),
            content: Text('Please enter both username and password.'),
            actions: <Widget>[
              TextButton(
                onPressed: () {
                  Navigator.of(context).pop();
                },
                child: Text('OK'),
              ),
            ],
          );
        },
      );
    } else {
      // Perform login logic here (e.g., validate credentials)
      // For simplicity, just show success message here
      showDialog(
        context: context,
        builder: (BuildContext context) {
          return AlertDialog(
            title: Text('Login Successful'),
            content: Text('Welcome, $username!'),
            actions: <Widget>[
              TextButton(
                onPressed: () {
                  Navigator.of(context).pop();
                },
                child: Text('OK'),
              ),
            ],
          );
        },
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Login Page'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextField(
              controller: usernameController,
              decoration: InputDecoration(
                labelText: 'Username',
                border: OutlineInputBorder(),
              ),
            ),
            SizedBox(height: 16.0),
            TextField(
              controller: passwordController,
              decoration: InputDecoration(
                labelText: 'Password',
                border: OutlineInputBorder(),
              ),
              obscureText: true,
            ),
            SizedBox(height: 16.0),
            ElevatedButton(
              onPressed: () {
                login(context);
              },
              child: Text('Login'),
            ),
          ],
        ),
      ),
    );
  }
}