update

android/app/src/main/AndroidManifest.xml

@@ -1,4 +1,6 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <uses-permission android:name="android.permission.USE_BIOMETRIC"/>
+    <uses-permission android:name="android.permission.USE_FINGERPRINT"/>
     <application
         android:label="Casha"
         android:name="${applicationName}"

android/app/src/main/kotlin/com/example/first_attempt/MainActivity.kt

@@ -1,5 +1,5 @@
 package com.example.casha
 
-import io.flutter.embedding.android.FlutterActivity
+import io.flutter.embedding.android.FlutterFragmentActivity
 
-class MainActivity : FlutterActivity()
+class MainActivity : FlutterFragmentActivity()

lib/core/services/biometric_service.dart

@@ -0,0 +1,37 @@
+import 'package:local_auth/local_auth.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class BiometricService {
+  static final _auth = LocalAuthentication();
+  static const _key = 'biometric_enabled';
+
+  static Future<bool> isAvailable() async {
+    final canCheck = await _auth.canCheckBiometrics;
+    final isSupported = await _auth.isDeviceSupported();
+    return canCheck && isSupported;
+  }
+
+  static Future<bool> isEnabled() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getBool(_key) ?? false;
+  }
+
+  static Future<void> setEnabled(bool value) async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(_key, value);
+  }
+
+  static Future<bool> authenticate() async {
+    try {
+      return await _auth.authenticate(
+        localizedReason: 'Confirm your identity to open Casha',
+        options: const AuthenticationOptions(
+          biometricOnly: false,
+          stickyAuth: true,
+        ),
+      );
+    } catch (_) {
+      return false;
+    }
+  }
+}

lib/features/settings/screen.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 import 'package:intl/intl.dart';
 import '../../core/constants.dart';
+import '../../core/services/biometric_service.dart';
 import '../../shared/utils/currency_utils.dart';
 import '../../shared/providers/amount_format_provider.dart';
 import '../dashboard/provider.dart';
@@ -387,6 +388,8 @@ class _SettingsScreenState extends ConsumerState<SettingsScreen> {
             ),
             const SizedBox(height: 16),
 
+            const _BiometricSection(),
+
             Container(
               padding: const EdgeInsets.all(20),
               decoration: BoxDecoration(
@@ -543,3 +546,106 @@ class _SettingsScreenState extends ConsumerState<SettingsScreen> {
     );
   }
 }
+
+class _BiometricSection extends StatefulWidget {
+  const _BiometricSection();
+
+  @override
+  State<_BiometricSection> createState() => _BiometricSectionState();
+}
+
+class _BiometricSectionState extends State<_BiometricSection> {
+  bool _available = false;
+  bool _enabled = false;
+  bool _loading = true;
+
+  @override
+  void initState() {
+    super.initState();
+    _load();
+  }
+
+  Future<void> _load() async {
+    final available = await BiometricService.isAvailable();
+    final enabled = await BiometricService.isEnabled();
+    if (mounted) {
+      setState(() {
+        _available = available;
+        _enabled = enabled;
+        _loading = false;
+      });
+    }
+  }
+
+  Future<void> _onToggle(bool val) async {
+    if (val) {
+      final ok = await BiometricService.authenticate();
+      if (!ok) return;
+    }
+    await BiometricService.setEnabled(val);
+    if (mounted) setState(() => _enabled = val);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if (_loading || !_available) return const SizedBox.shrink();
+    
+    final isDark = Theme.of(context).brightness == Brightness.dark;
+    
+    return Column(
+      children: [
+        Container(
+          padding: const EdgeInsets.all(20),
+          decoration: BoxDecoration(
+            color: Theme.of(context).colorScheme.surface,
+            borderRadius: BorderRadius.circular(16),
+            border: isDark ? null : Border.all(color: const Color(0xFFDDDDEE), width: 1),
+          ),
+          child: Row(
+            children: [
+              Container(
+                padding: const EdgeInsets.all(10),
+                decoration: BoxDecoration(
+                  color: AppColors.accent.withOpacity(0.15),
+                  borderRadius: BorderRadius.circular(12),
+                ),
+                child: const Icon(
+                  Icons.fingerprint,
+                  color: AppColors.accent,
+                  size: 20,
+                ),
+              ),
+              const SizedBox(width: 12),
+              Expanded(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(
+                      'Biometric Lock',
+                      style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                            fontWeight: FontWeight.w600,
+                            color: Theme.of(context).colorScheme.onSurface,
+                          ),
+                    ),
+                    Text(
+                      'Require fingerprint on app launch',
+                      style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                            color: Theme.of(context).colorScheme.onSurface.withOpacity(0.6),
+                          ),
+                    ),
+                  ],
+                ),
+              ),
+              Switch(
+                value: _enabled,
+                onChanged: _onToggle,
+                activeColor: const Color(0xFF7C6DED),
+              ),
+            ],
+          ),
+        ),
+        const SizedBox(height: 16),
+      ],
+    );
+  }
+}

lib/features/splash/screen.dart

@@ -1,6 +1,8 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:go_router/go_router.dart';
 import 'package:google_fonts/google_fonts.dart';
+import '../../core/services/biometric_service.dart';
 
 class SplashScreen extends StatefulWidget {
   const SplashScreen({super.key});
@@ -28,9 +30,17 @@ class _SplashScreenState extends State<SplashScreen> with SingleTickerProviderSt
 
     _controller.forward();
 
-    _controller.addStatusListener((status) {
+    _controller.addStatusListener((status) async {
       if (status == AnimationStatus.completed) {
         if (mounted) {
+          final isEnabled = await BiometricService.isEnabled();
+          if (isEnabled) {
+            final authenticated = await BiometricService.authenticate();
+            if (!authenticated) {
+              SystemNavigator.pop();
+              return;
+            }
+          }
           context.go('/dashboard');
         }
       }

macos/Flutter/GeneratedPluginRegistrant.swift

@@ -5,8 +5,10 @@
 import FlutterMacOS
 import Foundation
 
+import local_auth_darwin
 import shared_preferences_foundation
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
+  LocalAuthPlugin.register(with: registry.registrar(forPlugin: "LocalAuthPlugin"))
   SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
 }

pubspec.lock

@@ -166,6 +166,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "6.0.0"
+  flutter_plugin_android_lifecycle:
+    dependency: transitive
+    description:
+      name: flutter_plugin_android_lifecycle
+      sha256: ee8068e0e1cd16c4a82714119918efdeed33b3ba7772c54b5d094ab53f9b7fd1
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.0.33"
   flutter_riverpod:
     dependency: "direct main"
     description:
@@ -288,6 +296,46 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "6.1.0"
+  local_auth:
+    dependency: "direct main"
+    description:
+      name: local_auth
+      sha256: "434d854cf478f17f12ab29a76a02b3067f86a63a6d6c4eb8fbfdcfe4879c1b7b"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.3.0"
+  local_auth_android:
+    dependency: transitive
+    description:
+      name: local_auth_android
+      sha256: a0bdfcc0607050a26ef5b31d6b4b254581c3d3ce3c1816ab4d4f4a9173e84467
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.56"
+  local_auth_darwin:
+    dependency: transitive
+    description:
+      name: local_auth_darwin
+      sha256: "699873970067a40ef2f2c09b4c72eb1cfef64224ef041b3df9fdc5c4c1f91f49"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.6.1"
+  local_auth_platform_interface:
+    dependency: transitive
+    description:
+      name: local_auth_platform_interface
+      sha256: f98b8e388588583d3f781f6806e4f4c9f9e189d898d27f0c249b93a1973dd122
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.1.0"
+  local_auth_windows:
+    dependency: transitive
+    description:
+      name: local_auth_windows
+      sha256: bc4e66a29b0fdf751aafbec923b5bed7ad6ed3614875d8151afe2578520b2ab5
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.11"
   logging:
     dependency: transitive
     description:

pubspec.yaml

@@ -20,6 +20,7 @@ dependencies:
   path_provider: ^2.1.5
   http: ^1.2.0
   sensors_plus: ^6.1.0
+  local_auth: ^2.3.0
 
 flutter_launcher_icons:
   android: true

windows/flutter/generated_plugin_registrant.cc

@@ -6,6 +6,9 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <local_auth_windows/local_auth_plugin.h>
 
 void RegisterPlugins(flutter::PluginRegistry* registry) {
+  LocalAuthPluginRegisterWithRegistrar(
+      registry->GetRegistrarForPlugin("LocalAuthPlugin"));
 }

windows/flutter/generated_plugins.cmake

@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  local_auth_windows
 )
 
 list(APPEND FLUTTER_FFI_PLUGIN_LIST