💪 HealthTracker Android App

A full-featured health & fitness tracking Android application built with Java, Firebase, and the Gemini AI API — inspired by HealthifyMe.

---

✨ Features

Feature	Details
🔐 Authentication	Email/Password + Google Sign-In via Firebase Auth
👤 User Profiles	Onboarding wizard, BMR/TDEE auto-calculation
🍽 Food Logging	Meal tracking with full macro breakdown
🤖 AI Food Scan	Photo or gallery image → Gemini auto-detects food & nutrition
🔍 Food Search	Type a food name → Gemini returns nutrition info
💪 Workout Logging	Exercises, sets, reps, weight, duration, calories burned
📊 Daily Dashboard	Calorie ring, macro bars, water tracker, workout summary
📈 Progress Charts	7/14/30-day calorie trend, macro bar chart, workout duration
☁️ Real-time Sync	Firestore real-time listeners — data never lost
🗃 Offline-ready	Firestore offline persistence built-in

---

🚀 Setup Guide

1. Firebase Project

1. Go to Firebase Console and create a new project.
2. Add an Android app with package name: com.healthtracker
3. Download google-services.json and place it at:

   app/google-services.json
   

4. Enable Authentication → Sign-in methods:
   • Email/Password ✅
   • Google ✅ (copy the Web Client ID — you'll need it)
5. Enable Cloud Firestore → Start in production mode
6. Deploy Firestore security rules from firestore.rules

2. Google Sign-In

In app/src/main/res/values/strings.xml, replace:

<string name="default_web_client_id">YOUR_WEB_CLIENT_ID_HERE</string>

with your actual Web Client ID from Firebase Console → Authentication → Google → Web SDK configuration.

3. Gemini API Key

1. Get a free key at Google AI Studio
2. Add it to your local.properties file (never commit this file!):

   GEMINI_API_KEY=AIzaSy...your_key_here
   

   The build.gradle reads it automatically via BuildConfig.GEMINI_API_KEY.

4. Firestore Indexes

Some queries require composite indexes. Firestore will show error logs with direct links to create them. Create indexes for:

• food_entries: userId ASC + dateString ASC + createdAt ASC
• workout_entries: userId ASC + dateString ASC
• daily_summaries: userId ASC + dateString ASC

5. Add Jitpack (for MPAndroidChart)

In your root build.gradle, add Jitpack to allprojects.repositories:

allprojects {
    repositories {
        google()
        mavenCentral()
        maven { url 'https://jitpack.io' }  // ← ADD THIS
    }
}

---

📁 Project Structure

app/src/main/java/com/healthtracker/
├── activities/
│   ├── SplashActivity.java          # Entry point
│   ├── LoginActivity.java           # Email + Google auth
│   ├── RegisterActivity.java        # New account creation
│   ├── OnboardingActivity.java      # 3-step profile setup
│   ├── MainActivity.java            # Bottom nav host
│   ├── FoodLogActivity.java         # Log food + AI scan
│   └── WorkoutLogActivity.java      # Log workout + exercises
├── fragments/
│   ├── DashboardFragment.java       # Home screen
│   ├── FoodFragment.java            # Food log list
│   ├── WorkoutFragment.java         # Workout list
│   ├── ProgressFragment.java        # Charts & stats
│   └── ProfileFragment.java         # User profile
├── models/
│   ├── User.java                    # User + BMR/TDEE calc
│   ├── FoodEntry.java               # Meal entry
│   ├── WorkoutEntry.java            # Workout session
│   ├── Exercise.java                # Exercise + ExerciseSet
│   └── DailySummary.java            # Aggregated daily data
├── repositories/
│   ├── FirebaseRepository.java      # All Firestore operations
│   └── GeminiRepository.java        # Gemini Vision API calls
├── viewmodels/
│   └── DashboardViewModel.java      # LiveData + business logic
└── adapters/
    ├── FoodEntryAdapter.java        # RecyclerView for food
    ├── WorkoutEntryAdapter.java     # RecyclerView for workouts
    └── ExerciseAdapter.java         # Exercises + set rows

---

🏗 Architecture

UI (Activities/Fragments)
        ↓ observes LiveData
ViewModel (DashboardViewModel)
        ↓ calls
Repositories (FirebaseRepository, GeminiRepository)
        ↓ reads/writes
Firebase Firestore + Gemini REST API

• MVVM pattern with LiveData for reactive UI updates
• Real-time listeners via addSnapshotListener — dashboard updates instantly on any device
• Firestore transactions for atomic daily summary updates (no race conditions)
• Gemini 1.5 Flash for fast, cost-effective food image recognition

---

📊 Firestore Data Schema

users/{uid}
  - name, email, age, weightKg, heightCm
  - gender, activityLevel, goal
  - dailyCalorieGoal, dailyProteinGoalG, dailyCarbGoalG, dailyFatGoalG

food_entries/{autoId}
  - userId, foodName, mealType, dateString
  - calories, proteinG, carbsG, fatG, fiberG, sugarG, sodiumMg
  - servingSize, servingUnit, aiGenerated

workout_entries/{autoId}
  - userId, workoutName, workoutType, dateString
  - durationMinutes, caloriesBurned, intensityLevel
  - exercises: [ { name, category, sets: [{setNumber, weightKg, reps}] } ]

daily_summaries/{uid_YYYY-MM-DD}
  - userId, dateString
  - totalCaloriesConsumed, totalCaloriesBurned
  - totalProteinG, totalCarbsG, totalFatG
  - calorieGoal, workoutCount, workoutMinutes, waterLitres

---

🔧 Dependencies

Library	Purpose
Firebase Auth	User authentication
Firebase Firestore	Real-time cloud database
Google Play Services Auth	Google Sign-In
Gemini 1.5 Flash API	AI food image recognition
MPAndroidChart	Progress charts
Glide	Image loading
CircleImageView	Profile picture
Material Components 3	UI components
OkHttp + Gson	HTTP client for Gemini
Room	Local caching (optional extension)

---

⚡ Quick Calorie Estimation

The app uses the Mifflin-St Jeor equation for BMR and adjusts for activity level (TDEE):

• Sedentary → ×1.2
• Light → ×1.375
• Moderate → ×1.55
• Active → ×1.725
• Very Active → ×1.9

Goals adjust TDEE:

• Lose Weight: TDEE − 500 cal
• Maintain: TDEE
• Gain Muscle: TDEE + 300 cal

---

📱 Minimum Requirements

• Android 8.0 (API 26) or higher
• Internet connection for Firebase + Gemini
• Camera permission for AI food scanning