Configuration

Gemini API Configuration

The Gemini API key is critical for Vitu’s food analysis features. This section covers secure configuration practices.

Current Implementation

In the default setup, the API key is hardcoded in lib/main.dart:489:

main.dart

const apiKey = 'AIzaSyCEwgwToG9cfPvf2wzNHGOhSeXCLafD1ms';

Security Risk: Never commit real API keys to version control. The key in the source code is for demonstration only and should be replaced immediately.

Secure Configuration Methods

Option 1: Environment Variables (Recommended)

Install flutter_dotenv

Add to pubspec.yaml:

dependencies:
  flutter_dotenv: ^5.1.0

Run:

flutter pub get

Create .env file

Create .env in your project root:

GEMINI_API_KEY=your_actual_api_key_here

Add .env to .gitignore

Ensure .env is in your .gitignore:

echo ".env" >> .gitignore

Update main.dart

Replace the hardcoded key at line 489:

import 'package:flutter_dotenv/flutter_dotenv.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await dotenv.load(fileName: ".env");
  await Hive.initFlutter();
  // ... rest of initialization
}

Then in _HomeScreenState.initState() (line 484):

final apiKey = dotenv.env['GEMINI_API_KEY'] ?? '';
if (apiKey.isEmpty) {
  throw Exception('GEMINI_API_KEY not found in .env file');
}

Add .env to assets

In pubspec.yaml:

flutter:
  assets:
    - .env
    - assets/WhatsApp Image 2026-02-16 at 12.16.07 PM.jpeg

Option 2: Platform-Specific Configuration

Android: Store in android/local.properties (already in .gitignore):

gemini.api.key=your_actual_api_key_here

Access via native code or use a build-time code generation tool. iOS: Store in ios/Flutter/Secrets.xcconfig (add to .gitignore):

GEMINI_API_KEY=your_actual_api_key_here

Option 3: Firebase Remote Config

For production apps, consider Firebase Remote Config to:

Store keys server-side
Update keys without app redeployment
Implement feature flags

API Key Best Practices

Critical Security Guidelines:

✅ Store keys in environment variables or secure vaults
✅ Add key files to .gitignore
✅ Use different keys for development and production
✅ Rotate keys regularly
✅ Set up usage limits in Google Cloud Console
❌ Never commit keys to Git
❌ Never share keys publicly
❌ Never hardcode keys in production builds

Obtaining a Gemini API Key

Visit Google AI Studio

Go to aistudio.google.com/app/apikey

Create API key

Click “Create API key” and select a Google Cloud project (or create a new one).

Copy the key

Copy the generated key immediately. It won’t be shown again.

Configure usage limits

In Google Cloud Console:

Enable the Generative Language API
Set quotas and rate limits
Enable billing alerts

Platform Permissions

Vitu requires several device permissions to function. These are already configured in the source but can be customized.

Android Permissions

Configured in android/app/src/main/AndroidManifest.xml:2-3:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

Purpose:

ACCESS_FINE_LOCATION - GPS-based step tracking and activity detection
ACCESS_COARSE_LOCATION - Fallback location for step counting

Runtime Permissions: The geolocator package automatically handles runtime permission requests. Users will see a system dialog when the Exercise screen first accesses location.

iOS Permissions

Configured in ios/Runner/Info.plist:48-51:

<key>NSLocationWhenInUseUsageDescription</key>
<string>Necesitamos ubicación para contar pasos y detectar actividad</string>
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>Necesitamos ubicación para contar pasos y detectar actividad</string>

Customization: To change the permission request message, edit the <string> values:

<key>NSLocationWhenInUseUsageDescription</key>
<string>Vitu needs your location to count steps and detect if you're in a vehicle</string>

Camera and Photo Library

Handled automatically by the image_picker plugin. No manual configuration needed. iOS Auto-Configuration:

Camera: Prompts on first use
Photo Library: Prompts on first use

Android Auto-Configuration:

Camera: No permission required on Android 11+
Storage: Uses scoped storage (no permission required)

Motion Sensors

Accelerometer access via sensors_plus requires no explicit permissions on Android or iOS.

App Configuration

Hive Database Initialization

Vitu initializes Hive in main() at lib/main.dart:21-28:

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Hive.initFlutter();
  await Hive.openBox('users');
  await Hive.openBox('user_settings');
  await Hive.openBox('daily_exercise');
  await Hive.openBox('hydration_logs');
  await Hive.openBox('daily_hydration_summary');
  SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersiveSticky);
  runApp(const MyApp());
}

Boxes:

users - User profiles and authentication
user_settings - Theme, preferences, hydration goals
daily_exercise - Step counts and activity data
hydration_logs - Individual water intake events
daily_hydration_summary - Aggregated daily totals

Adding New Boxes: To add a new data collection:

await Hive.openBox('my_new_feature');

Then access it anywhere:

Box get _myFeatureBox => Hive.box('my_new_feature');

User Settings

User settings are stored per-user in the user_settings box with the key settings:{userId}. Available Settings: See UserSettings class in lib/main.dart:161-200:

class UserSettings {
  final String userId;
  final String? brightness;        // 'light' | 'dark'
  final int? seedColor;            // ARGB color int
  final String? fontFamily;        // null | 'serif' | etc.
  final bool? followLocation;      // Enable location tracking
  final double? metaHydratationMl; // Custom hydration goal
}

Accessing Settings:

final settings = getSettingsForUser(userEmail);
if (settings?.brightness == 'dark') {
  // Use dark theme
}

Saving Settings:

await saveSettings(UserSettings(
  userId: currentUser.correo,
  brightness: 'dark',
  seedColor: colorToArgb(Colors.blue),
  metaHydratationMl: 2500.0,
));

Hydration Goal Calculation

The default hydration goal is calculated in lib/main.dart:202-209:

double computeDailyHydrationGoalMl(User u) {
  final base = (u.peso > 0 ? u.peso : 70.0) * 35.0;
  double adj = base;
  if (u.edad > 0 && u.edad < 14) adj = base * 0.9;
  if (u.edad >= 65) adj = base * 0.95;
  if (u.genero.toLowerCase() == 'masculino') adj += 200;
  return adj.clamp(1200.0, 4500.0);
}

Formula:

Base: weight_kg * 35ml
Age less than 14: -10%
Age 65 or older: -5%
Male: +200ml
Clamped to 1200-4500ml

Customization: To change the formula, edit the function above. Example - increase base rate:

final base = (u.peso > 0 ? u.peso : 70.0) * 40.0; // Changed from 35 to 40

Theme Configuration

Vitu uses Material 3 with dynamic theming. The theme is configured in lib/main.dart:44-52:

MaterialApp(
  title: 'Vitu',
  debugShowCheckedModeBanner: false,
  theme: ThemeData(
    colorScheme: ColorScheme.fromSeed(seedColor: Colors.lime),
    useMaterial3: true,
  ),
  home: const SplashScreen(),
)

Default Seed Color: Colors.lime User-Customizable: Users can change the seed color from Settings, which updates the entire app theme dynamically. The color is stored in UserSettings.seedColor as an ARGB integer.

Adding Custom Fonts

Add font files

Create fonts/ directory and add .ttf files:

fonts/
  Roboto-Regular.ttf
  Roboto-Bold.ttf

Declare in pubspec.yaml

flutter:
  fonts:
    - family: Roboto
      fonts:
        - asset: fonts/Roboto-Regular.ttf
        - asset: fonts/Roboto-Bold.ttf
          weight: 700

Use in Settings

The font family is already configurable via UserSettings.fontFamily. Users can select from available fonts in the Settings screen.

Environment Variables Reference

Recommended .env structure:

# Google AI (Gemini)
GEMINI_API_KEY=your_gemini_key_here
GEMINI_MODEL=gemini-2.5-flash

# App Configuration
APP_NAME=Vitu
DEFAULT_HYDRATION_GOAL_ML=2000

# Debug Flags
ENABLE_DEBUG_LOGGING=false

Accessing in code:

final apiKey = dotenv.env['GEMINI_API_KEY']!;
final modelName = dotenv.env['GEMINI_MODEL'] ?? 'gemini-2.5-flash';

Security Best Practices

Critical: Production Security ChecklistBefore deploying Vitu:✅ Remove all hardcoded API keys✅ Use environment variables or secure vaults✅ Add .env, local.properties, and secrets files to .gitignore✅ Enable API key restrictions in Google Cloud Console:

Restrict to specific APIs (Generative Language API only)
Set up usage quotas
Enable billing alerts

✅ Implement rate limiting for AI requests✅ Consider hashing passwords if adding backend authentication (currently stored as plaintext in local Hive)✅ Review all platform permissions - request only what’s necessary✅ Test permission flows on both Android and iOS

Password Storage

Current Implementation: User passwords are stored as plaintext in the local Hive database.This is acceptable for a local-only app, but if you add backend authentication, you MUST:

Hash passwords using bcrypt, argon2, or similar
Use secure communication (HTTPS)
Implement proper authentication tokens

Example secure password storage:

import 'package:crypto/crypto.dart';
import 'dart:convert';

String hashPassword(String password) {
  final bytes = utf8.encode(password);
  final digest = sha256.convert(bytes);
  return digest.toString();
}

bool verifyPassword(String input, String hashed) {
  return hashPassword(input) == hashed;
}

Data Privacy

Vitu is designed with privacy in mind: Local-First:

All user data stored locally in Hive (NoSQL)
No backend servers
No data synchronization

External Data Sharing:

Food images sent to Google Gemini API for analysis
Location coordinates used locally for step tracking (not sent externally)

User Control:

Users can delete the app to remove all data
No analytics or tracking by default

Compliance Recommendations: If deploying publicly:

Add a privacy policy explaining Gemini API usage
Inform users that food images are sent to Google
Provide opt-in/opt-out for AI features
Comply with GDPR, CCPA if applicable

Advanced Configuration

Sleep Detection Window

Sleep is detected between 19:00 and 07:00 with a 10-minute margin. To customize, find the sleep detection logic in the SleepScreen widget. Current window: 19:00 - 07:00 (7 PM to 7 AM) To change: Search for 19:00 and 07:00 in lib/main.dart and adjust.

Step Counting Threshold

Steps are ignored when moving >15 km/h (vehicle detection). To adjust, find the speed check in ExerciseScreen. Current threshold: 15 km/h To change: Search for velocity/speed checks in the Exercise screen logic.

Gemini Model Selection

The app uses gemini-2.5-flash (configured in lib/main.dart:493):

_geminiModel = GenerativeModel(
  model: 'gemini-2.5-flash',
  apiKey: apiKey,
);

Alternative models:

gemini-pro-vision - Better image understanding, slower
gemini-pro - Text only (no images)

To change the model, update the model: parameter.

Troubleshooting

API key not working

Verify the key is active in Google AI Studio
Check that Generative Language API is enabled
Ensure no usage quotas are exceeded
Try generating a new key

Hive database corruption

flutter clean
flutter pub get

On the device, uninstall and reinstall the app to reset the database.

Permission denied errors

Android: Check Settings → Apps → Vitu → Permissions
iOS: Settings → Vitu → Location/Camera
Ensure AndroidManifest.xml and Info.plist have the correct entries

Next Steps

Explore the Quickstart guide to use all features
Review lib/main.dart for implementation details
Customize colors, fonts, and behavior
Add new features following the Hive database pattern

Overview

Setup

Configuration

Gemini API Configuration

Current Implementation

Secure Configuration Methods

Option 1: Environment Variables (Recommended)

Option 2: Platform-Specific Configuration

Option 3: Firebase Remote Config

API Key Best Practices

Obtaining a Gemini API Key

Platform Permissions

Android Permissions

iOS Permissions

Camera and Photo Library

Motion Sensors

App Configuration

Hive Database Initialization

User Settings

Hydration Goal Calculation

Theme Configuration

Adding Custom Fonts

Environment Variables Reference

Security Best Practices

Password Storage

Data Privacy

Advanced Configuration

Sleep Detection Window

Step Counting Threshold

Gemini Model Selection

Troubleshooting

API key not working

Hive database corruption

Permission denied errors

Next Steps

Build docs developers (and LLMs) love

Overview

Setup

​Gemini API Configuration

​Current Implementation

​Secure Configuration Methods

​Option 1: Environment Variables (Recommended)

​Option 2: Platform-Specific Configuration

​Option 3: Firebase Remote Config

​API Key Best Practices

​Obtaining a Gemini API Key

​Platform Permissions

​Android Permissions

​iOS Permissions

​Camera and Photo Library

​Motion Sensors

​App Configuration

​Hive Database Initialization

​User Settings

​Hydration Goal Calculation

​Theme Configuration

​Adding Custom Fonts

​Environment Variables Reference

​Security Best Practices

​Password Storage

​Data Privacy

​Advanced Configuration

​Sleep Detection Window

​Step Counting Threshold

​Gemini Model Selection

​Troubleshooting

​API key not working

​Hive database corruption

​Permission denied errors

​Next Steps

Build docs developers (and LLMs) love

Gemini API Configuration

Current Implementation

Secure Configuration Methods

Option 1: Environment Variables (Recommended)

Option 2: Platform-Specific Configuration

Option 3: Firebase Remote Config

API Key Best Practices

Obtaining a Gemini API Key

Platform Permissions

Android Permissions

iOS Permissions

Camera and Photo Library

Motion Sensors

App Configuration

Hive Database Initialization

User Settings

Hydration Goal Calculation

Theme Configuration

Adding Custom Fonts

Environment Variables Reference

Security Best Practices

Password Storage

Data Privacy

Advanced Configuration

Sleep Detection Window

Step Counting Threshold

Gemini Model Selection

Troubleshooting

API key not working

Hive database corruption

Permission denied errors

Next Steps