Screen Time Calculator

A comprehensive parental control Android application that helps children earn phone usage time by completing real-world tasks approved by parents.

🎯 Overview

Screen Time Calculator is a parent-child linked mobile application that:

• Allows children to earn phone usage time by completing tasks
• Enforces time limits through Android Device Owner controls
• Blocks all apps when earned time runs out
• Provides parents with complete control and monitoring

✨ Key Features

For Parents

• Create and manage family accounts
• Define daily tasks with customizable rewards
• Approve or reject completed tasks in real-time
• Monitor child's app usage and screen time
• View detailed reports and analytics
• Emergency unlock capability
• Security event notifications

For Children

• View assigned daily tasks
• Mark tasks as completed
• Real-time time balance tracking
• Countdown timer display
• Earn minutes through task completion
• Gamified task interface

Security Features

• Device Owner Mode: Prevents uninstall and bypass attempts
• Time Validation: Detects system time manipulation using NTP
• Root Detection: Identifies rooted devices
• Integrity Checking: Validates app hasn't been tampered with
• App Blocking: Complete device lockdown when time depletes
• Kiosk Mode: Only Screen Time app accessible when blocked
• Anti-Bypass: Multiple layers of security protection

🏗️ Architecture

Technology Stack

Frontend (Android)

• Language: Kotlin
• UI: Jetpack Compose with Material Design 3
• Architecture: Clean Architecture (MVVM)
• DI: Hilt
• Async: Coroutines + Flow
• Local DB: Room
• Preferences: DataStore

Backend (Firebase)

• Authentication: Firebase Auth
• Database: Cloud Firestore
• Functions: Cloud Functions (TypeScript)
• Messaging: Firebase Cloud Messaging (FCM)
• Analytics: Firebase Analytics
• Monitoring: Firebase Crashlytics

Device Management

• DevicePolicyManager (Device Owner)
• UsageStatsManager
• ForegroundService
• WorkManager

Project Structure

Android-app/
├── app-parent/              # Parent app (Master)
├── app-child/               # Child app (Slave) - THIS IS THE MAIN APP
│   ├── service/             # Time tracking, app blocking, device admin
│   ├── security/            # Anti-bypass, root detection, integrity checks
│   ├── ui/                  # Jetpack Compose UI
│   └── di/                  # Dependency injection
├── core/
│   ├── model/               # Shared data models
│   ├── common/              # Utilities and extensions
│   ├── designsystem/        # Material 3 theme
│   ├── network/             # Firebase integration
│   └── database/            # Room database
├── backend/
│   └── functions/           # Firebase Cloud Functions
└── docs/                    # Documentation

🚀 Quick Start

Prerequisites

• Android Studio Hedgehog or later
• JDK 17
• Android SDK API 34
• Firebase account
• Node.js 18+ (for Cloud Functions)

1. Clone Repository

git clone https://github.com/yourusername/Android-app.git
cd Android-app

2. Firebase Setup

1. Create a new Firebase project at Firebase Console
2. Enable Authentication (Email/Password)
3. Enable Firestore Database
4. Enable Cloud Messaging
5. Download google-services.json for the child app
6. Place it in app-child/google-services.json

3. Build the App

# Build child app (release)
./gradlew :app-child:assembleRelease

# The APK will be at: app-child/build/outputs/apk/release/app-child-release.apk

4. Device Owner Setup (CRITICAL)

⚠️ IMPORTANT: The child app MUST be set as Device Owner to function properly.

See DEVICE_OWNER_SETUP.md for detailed instructions.

Quick summary:

# 1. Factory reset the child's device
# 2. During setup, skip Google account
# 3. Enable USB debugging
# 4. Connect to computer
# 5. Install app
adb install app-child-release.apk

# 6. Set as Device Owner
adb shell dpm set-device-owner com.screetime.child/.service.ScreenTimeDeviceAdminReceiver

# 7. Verify
adb shell dumpsys device_policy | grep "Device Owner"

5. Deploy Cloud Functions

cd backend
npm install
npm run build
firebase deploy --only functions

📱 How It Works

Daily Flow

1. Morning

   • Child wakes up with 0 minutes of screen time
   • Views assigned tasks for the day
   • Completes tasks (e.g., make bed, brush teeth)
   • Marks tasks as completed in app

2. Parent Approval

   • Parent receives notification of completed task
   • Reviews task completion
   • Approves or rejects with optional feedback
   • Upon approval, minutes are automatically added

3. Screen Time Usage

   • Child uses phone for earned minutes
   • Countdown timer runs continuously
   • Warnings at 5 minutes and 1 minute remaining
   • When time reaches 0, all apps are blocked

4. Blocked Mode

   • Only Screen Time app is accessible (kiosk mode)
   • Shows available tasks to earn more time
   • Emergency unlock request option
   • Cannot exit or bypass the app

5. Midnight Reset

   • Automatic daily reset at midnight
   • Tasks return to "Pending" status
   • Time balance resets to 0
   • New day begins

🔒 Security Model

Device Owner Enforcement

The app uses Android's Device Owner mode to ensure parental controls cannot be bypassed:

• Uninstall Prevention: App cannot be uninstalled without factory reset
• App Blocking: Hide and suspend all other apps when time depletes
• Kiosk Mode: Lock device to Screen Time app only
• Policy Enforcement: Disable USB debugging, developer options, etc.

Anti-Bypass Mechanisms

1. Time Manipulation Detection

   • Validates system time against NTP servers
   • Cross-references with Firebase server time
   • Detects manual time changes
   • Logs security events

2. Root Detection

   • Checks for su binaries
   • Scans for root management apps
   • Validates build tags
   • Tests system write permissions

3. Integrity Validation

   • Verifies app signature
   • Checks installation source
   • Detects ADB/developer mode
   • Uses Play Integrity API

4. Service Protection

   • Foreground services with high priority
   • Automatic restart after device reboot
   • Protection against force-stop
   • Background task monitoring

📊 Default Tasks

The app comes with pre-configured tasks:

Task	Reward	Description
Make bed	10 min	Make your bed neatly
Brush teeth (morning)	5 min	Brush your teeth in the morning
Brush teeth (evening)	5 min	Brush your teeth before bed
Homework	30 min	Complete your homework
Reading (20 min)	20 min	Read for 20 minutes
Clean room	15 min	Clean and organize your room
Help with dishes	10 min	Help wash or dry the dishes
Physical activity (30 min)	20 min	Exercise or play outside
Prepare school bag	5 min	Pack your school bag for tomorrow

Parents can customize rewards and add new tasks.

🎮 Future Enhancements

• Parent mobile app (currently planned)
• Weekly/monthly task templates
• Achievement badges and rewards
• Scheduled bedtime auto-lock
• Multiple children per family
• App-specific time limits
• Educational content integration
• Parental web dashboard

⚠️ Important Notes

Legal & Privacy

• This app is intended for parental supervision of minors
• Ensure compliance with local laws regarding parental monitoring
• Privacy policy must be provided for Play Store submission
• Obtain informed consent from children (age-appropriate)

Device Requirements

• Minimum: Android 8.0 (API 26)
• Target: Android 14 (API 34)
• Device owner setup requires factory reset or new device
• Not compatible with existing Google accounts as primary

Limitations

• Android Only: iOS version has significant limitations
• One Device: Child can only use one device with this app
• Factory Reset Required: Device owner setup needs clean device
• No Multi-User: Android multi-user mode may interfere

📚 Documentation

• Setup Guide - Detailed setup instructions
• Device Owner Setup - Critical device configuration
• Deployment Guide - Production deployment
• Architecture - Technical architecture details
• API Documentation - Firebase Cloud Functions API
• Security - Security implementation details

🤝 Contributing

This is a private project. If you'd like to contribute, please contact the repository owner.

📄 License

Copyright © 2024. All rights reserved.

🆘 Support

For issues and questions:

1. Check the Documentation
2. Review Common Issues
3. Open an issue on GitHub

⚙️ Build Information

• Version: 1.0.0
• Build Tools: Gradle 8.4, AGP 8.2.2
• Kotlin Version: 1.9.22
• Min SDK: 26 (Android 8.0)
• Target SDK: 34 (Android 14)

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⚠️ CRITICAL: This app requires Device Owner privileges to function. Standard installation will NOT work. You MUST follow the Device Owner setup procedure.