FitNotes Research & Reverse Engineering

This repository contains comprehensive research and analysis of the FitNotes Android workout tracking app, with the goal of creating a compatible cross-platform alternative using Expo/React Native.

Current Status: v1.2.0 🚀 - FitNotes parity complete + AI Insights + Social Sharing, see Project Status

🌟 What's New in v1.2.0

• 🤖 AI Workout Insights (v1.1.0): On-device analysis with rest day recommendations, volume overload warnings, plateau detection, and workout duration insights
• 📤 Social Sharing (v1.2.0): Share beautiful workout summary cards as images to any platform
• 100% Offline: All features work without internet - privacy-first, no cloud required

� Quick Start

Development

cd workout-tracker
npm install
npm start              # Start Expo dev server
npm run android        # Run on Android
npm run ios            # Run on iOS

Version Management

npm run version:bump:patch     # 1.2.0 → 1.2.1 (bug fixes)
npm run version:bump:minor     # 1.2.0 → 1.3.0 (new features)
npm run version:bump:major     # 1.2.0 → 2.0.0 (breaking changes)

Building

npm run build:android:preview  # APK for testing
npm run build:ios:preview      # IPA for testing
npm run build:production       # AAB + IPA for app stores

Full details: BUILD_AND_RELEASE.md

�📁 Repository Structure

fitnotes-research/
├── workout-tracker/               # Expo/React Native app (main implementation)
│   ├── app/                       # Expo Router screens
│   ├── src/                       # Core logic, services, components
│   ├── assets/                    # Images, fonts, icons
│   └── ...
├── docs/                          # Organized documentation
│   ├── research/                  # FitNotes reverse engineering docs
│   │   ├── FITNOTES_EXPORT_FORMAT.md
│   │   ├── FITNOTES_UI_FEATURES.md
│   │   ├── IMPLEMENTATION_GUIDE.md
│   │   └── ...
│   ├── development/               # Current project status
│   │   └── PROJECT_STATUS.md
│   ├── bugs/                      # Bug tracking and resolution
│   │   ├── BUG_STATUS.md
│   │   ├── BUGS_FOUND.md
│   │   └── BUGS_ANALYSIS_FEATURE.md
│   └── archive/                   # Historical session notes
│       ├── AUTOPILOT_SESSION_COMPLETE.md
│       ├── IMPLEMENTATION_SESSION_SUMMARY.md
│       ├── IMPLEMENTATION_GAP_ANALYSIS.md
│       └── ROADMAP_AND_MONETIZATION.md
├── apk/                           # Original FitNotes APK
├── extracted/                     # Unzipped APK contents
├── decompiled/                    # Decompiled Java source code
│   ├── sources/                   # Readable Java source
│   └── resources/                 # Decompiled resources
└── README.md                      # This file

📋 Quick Links

• 📊 Project Status - Current implementation status, roadmap, and completion percentage
• 🐛 Bug Status - Known issues, fixes, and tracking
• 📂 Workout Tracker App - Main React Native implementation

📋 Documentation

1. FitNotes Export Format

Comprehensive documentation of:

• CSV Export Format - Exact structure of workout and measurement exports
• Database Schema - SQLite tables and relationships
• Data Models - TypeScript interfaces for all entities
• Export Logic - How FitNotes generates CSV files
• Import Requirements - What's needed to import FitNotes data
• Code Examples - TypeScript functions for export/import

Key Findings:

• Workout CSV: Date,Exercise,Category,Weight,Weight Unit,Reps,Distance,Distance Unit,Time,Comment
• Measurement CSV: Date,Time,Measurement,Value,Unit,Comment
• Weights stored internally as metric (kg)
• Multiple exercise types (weight+reps, cardio, timed, etc.)
• Support for comments, personal records, workout groups

2. FitNotes UI & Features

Detailed analysis of:

• Main Features - Workout logging, exercise management, calendar, graphs, etc.
• UI Patterns - Material Design components and layouts
• Navigation Structure - Screen hierarchy and user flows
• Data Visualization - Graphs, charts, calendar views
• Settings & Customization - Units, themes, rest timers, etc.
• Feature Prioritization - What to implement first

Core Features Identified:

• ✅ Workout logging with 6 exercise types
• ✅ Exercise & category management
• ✅ CSV export/import
• ✅ Progress graphs
• ✅ Calendar view
• ✅ Personal records tracking
• ✅ Body measurements
• ✅ Routines & templates
• ✅ Goals & workout groups
• ✅ Plate calculator & 1RM estimation

3. Implementation Guide

Step-by-step guide for building a compatible Expo app:

• Project Setup - Dependencies and folder structure
• Database Setup - SQLite schema matching FitNotes
• CSV Export Function - Complete TypeScript implementation
• CSV Import Function - Parse and import FitNotes CSV
• UI Components - Example screens (Home, Settings, etc.)
• Testing Workflow - How to verify compatibility
• Deployment - Build and publish to app stores

Tech Stack Recommended:

• Framework: Expo (React Native)
• Database: expo-sqlite
• Navigation: React Navigation
• UI: React Native Paper
• State: Zustand
• Charts: Victory Native

🔧 How This Was Done

Tools Used

1. jadx - DEX to Java decompiler

   • Decompiled APK to readable Java source
   • Preserved structure and comments
   • Generated both sources and resources

2. unzip - APK extraction

   • APK is just a ZIP archive
   • Extracted raw resources and manifests

3. grep/find - Code analysis

   • Searched for export/import logic
   • Found database schemas
   • Identified key classes

Process

1. ✅ Extract APK - Unzipped APK to access raw files
2. ✅ Decompile - Used jadx to convert DEX to Java
3. ✅ Analyze Export - Found ExportManager, WorkoutExportDataLoader, CsvWriter
4. ✅ Map Database - Discovered table schemas and relationships
5. ✅ Document Format - Reverse-engineered exact CSV structure
6. ✅ Research UI - Analyzed activities, fragments, layouts
7. ✅ Identify Features - Catalogued all app features
8. ✅ Create Guide - Wrote implementation roadmap

🎯 Key Insights

CSV Format (Critical for Compatibility)

Date,Exercise,Category,Weight,Weight Unit,Reps,Distance,Distance Unit,Time,Comment
2024-03-20,Bench Press,Chest,100,kg,10,,,,,
2024-03-20,Running,Cardio,,,,,5.0,km,00:25:30,

Rules:

• Date format: YYYY-MM-DD
• Empty fields: empty string, not null
• Comments: optional 10th column
• Units: kg/lbs/st, km/mi/m
• Time: HH:MM:SS or MM:SS

Database Schema (Simplified)

category → exercise → training_log
                   ↓
                comment

Exercise Types

1. Weight + Reps - Bench Press, Squats
2. Bodyweight + Reps - Pull-ups, Push-ups
3. Cardio - Running, Cycling (Distance + Time)
4. Timed - Plank (Time only)
5. Weight Only - Deadlift 1RM
6. Reps Only - Jumping jacks

🚀 Getting Started with Your App

Quick Start

# Create new Expo project
npx create-expo-app my-workout-app --template expo-template-blank-typescript

cd my-workout-app

# Install dependencies
npx expo install expo-sqlite expo-file-system expo-sharing \
  react-native-paper @react-navigation/native

# Copy implementation code from IMPLEMENTATION_GUIDE.md

# Start development
npx expo start

Implementation Phases

1. Phase 1 (Week 1-2): Database + CSV Import/Export
2. Phase 2 (Week 3-4): Core UI (Home, Workout Log, Exercise List)
3. Phase 3 (Week 5): Settings, Export/Import UI
4. Phase 4 (Week 6+): Graphs, Calendar, Advanced Features

Testing Compatibility

1. Export data from FitNotes
2. Import into your app
3. Verify data accuracy
4. Export from your app
5. Re-import into FitNotes ✅

📊 Feature Comparison

Feature	FitNotes	Your MVP	Priority
Workout Logging	✅	✅	🔴 Critical
CSV Export	✅	✅	🔴 Critical
CSV Import	✅	✅	🔴 Critical
Exercise Management	✅	✅	🔴 Critical
Categories	✅	✅	🔴 Critical
Basic Graphs	✅	⚠️	🟠 High
Calendar View	✅	⚠️	🟠 High
Personal Records	✅	⚠️	🟡 Medium
Body Measurements	✅	⚠️	🟡 Medium
Routines	✅	⚠️	🟡 Medium
Goals	✅	❌	🟢 Low
Plate Calculator	✅	❌	🟢 Low

Legend:

• ✅ Fully implemented
• ⚠️ Partially implemented or planned
• ❌ Not implemented

💡 Why This Matters

FitNotes Limitations

• ❌ Android only (no iOS)
• ❌ No web version
• ❌ No cloud sync
• ❌ Limited API/integration
• ❌ Closed source
• ❌ No active development (last update 2023)

Your App Advantages

• ✅ Cross-platform (iOS, Android, Web)
• ✅ Cloud sync (optional)
• ✅ Modern UI/UX
• ✅ Active development
• ✅ Open source (if you choose)
• ✅ 100% FitNotes data compatible

📝 Important Notes

Legal & Ethical

• This is reverse engineering for interoperability
• Not copying FitNotes app
• Creating a compatible alternative
• FitNotes exports are user's data
• CSV format is not copyrightable

Package Info

• Package: com.github.jamesgay.fitnotes
• Version: 25.1 (analyzed)
• Source: APKPure

File Locations (in decompiled code)

• Export Manager: X0/j.java (ExportManager.kt)
• Workout Export: Z0/c.java (WorkoutExportDataLoader.kt)
• Measurement Export: Z0/b.java (MeasurementExportDataLoader.kt)
• CSV Writer: Y0/b.java (CsvWriter.kt)
• Training Log DB: X/J0.java
• Models: com/github/jamesgay/fitnotes/model/

🎓 Learning from FitNotes

What FitNotes Does Well

• ✨ Simple, intuitive UI
• ✨ Fast workout entry
• ✨ Comprehensive tracking (6 exercise types)
• ✨ Excellent data export (CSV)
• ✨ Offline-first (no internet required)
• ✨ Respectful of user data

What Could Be Improved

• 📱 iOS version
• ☁️ Optional cloud backup
• 🎨 Modern Material Design 3
• 🔄 Automatic sync
• 🌐 Web version
• 🤝 Social features (optional)
• 📊 More visualizations

🛠️ Development Roadmap

Milestone 1: Data Compatibility ✅

• Understand FitNotes CSV format
• Create database schema
• Implement CSV export
• Implement CSV import
• Test with real FitNotes data

Milestone 2: Core Features

• Home screen with recent workouts
• Workout logging interface
• Exercise management
• Category system
• Settings screen

Milestone 3: Visualizations

• Exercise graphs (line charts)
• Calendar view
• Statistics dashboard
• Progress tracking

Milestone 4: Advanced Features

• Personal records
• Routines/templates
• Body measurements
• Goals tracking
• Rest timer

Milestone 5: Polish & Deploy

• App icons & splash screens
• Onboarding flow
• App store optimization
• Beta testing
• Public release 🚀

🤝 Contributing

If you're building on this research:

1. ⭐ Star this repo
2. 📝 Document your findings
3. 🔄 Share improvements
4. 🐛 Report issues
5. 💡 Suggest features

📚 Additional Resources

FitNotes

• Play Store
• Reddit Community

Development

• Expo Documentation
• React Native
• React Native Paper
• SQLite

Android Reverse Engineering

• jadx
• APKTool

📄 License

This research documentation is provided for educational and interoperability purposes.

Research & Documentation: MIT License
FitNotes App: © Original developer (not affiliated)
Your Implementation: Your choice of license

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🙏 Acknowledgments

• FitNotes Developer - For creating an excellent workout tracking app
• jadx Team - For the amazing decompilation tool
• Expo Team - For making cross-platform development accessible
• Open Source Community - For the tools and libraries

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⚡ Quick Links

• 📖 Export Format Documentation
• 🎨 UI & Features Documentation
• 🚀 Implementation Guide

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Status: ✅ Research Complete | 🚧 Implementation Ready

Last Updated: March 22, 2026

Questions? Open an issue or start a discussion!