BMI Calculator Android App

A modern, animated Android application for calculating Body Mass Index (BMI) with a beautiful user interface and smooth animations.

📱 Features

Core Functionality

• BMI Calculation: Calculate BMI using weight and height inputs
• Multiple Unit Support:
  • Weight: kg, pounds, stones
  • Height: cm, feet, meters
• Real-time Conversion: Automatic unit conversion for accurate calculations
• BMI Categories: Visual reference table showing BMI classifications

User Interface

• Animated Splash Screen: Lottie animations for engaging user experience
• Modern Design: Purple/blue gradient theme with semi-transparent elements
• Responsive Layout: Optimized for different screen sizes
• Smooth Animations: Background Lottie animations for visual appeal

BMI Categories Display

BMI Range	Category	Color
≤ 18.4	Underweight	Light Yellow
18.5 - 24.9	Normal	Green
25.0 - 39.9	Overweight	Orange
≥ 40.0	Obese	Red

📱 UI of the App

main.mp4

🛠️ Technical Stack

• Language: Java
• Minimum SDK: API 24 (Android 7.0)
• Target SDK: API 34 (Android 14)
• Compile SDK: API 35
• Architecture: Single Activity with Splash Screen
• UI Framework: ConstraintLayout
• Animations: Lottie (Airbnb)
• Build System: Gradle

📋 Prerequisites

• Android Studio Arctic Fox or later
• Android SDK API 24+
• Java Development Kit (JDK) 11
• Gradle 8.9+

🚀 Installation & Setup

1. Clone the Repository

git clone https://github.com/yourusername/bmi-calculator.git
cd bmi-calculator

2. Open in Android Studio

• Open Android Studio
• Select "Open an existing Android Studio project"
• Navigate to the cloned directory and select it

3. Sync Project

• Wait for Gradle sync to complete
• If prompted, update Gradle wrapper version

4. Build and Run

• Connect an Android device or start an emulator
• Click the "Run" button (green play icon) or press Shift + F10

📁 Project Structure

app/
├── src/main/
│   ├── java/com/harsh/bmi/
│   │   ├── MainActivity.java          # Main BMI calculation logic
│   │   └── SplashActivity.java        # Animated splash screen
│   ├── res/
│   │   ├── layout/
│   │   │   ├── activity_main.xml      # Main UI layout
│   │   │   └── activity_splash.xml    # Splash screen layout
│   │   ├── values/
│   │   │   ├── strings.xml            # String resources
│   │   │   ├── colors.xml             # Color definitions
│   │   │   └── themes.xml             # App themes
│   │   ├── drawable/                  # Custom drawables
│   │   └── raw/                       # Lottie animation files
│   └── AndroidManifest.xml
└── build.gradle.kts                   # App-level build configuration

🎨 Key Components

MainActivity.java

• Handles BMI calculation logic
• Manages unit conversions (feet to meters, pounds to kg, etc.)
• Implements input validation
• Controls UI state and visibility

SplashActivity.java

• Provides animated splash screen
• Uses Lottie animations for smooth transitions
• Implements proper splash screen lifecycle management

Layout Files

• activity_main.xml: Complex ConstraintLayout with multiple Lottie animations
• activity_splash.xml: Full-screen splash with centered animation

🔧 Dependencies

dependencies {
    implementation 'androidx.appcompat:appcompat:1.6.1'
    implementation 'com.google.android.material:material:1.11.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    implementation 'androidx.core:core-splashscreen:1.0.0'
    implementation 'com.airbnb.android:lottie:6.4.0'
}

🚀 Usage

1. Launch the App: The app starts with an animated splash screen
2. Enter Measurements:
   • Input your weight in the first field
   • Select weight unit (kg/pounds/stones)
   • Input your height in the second field
   • Select height unit (cm/feet/meters)
3. Calculate BMI: Tap the "BMI" button
4. View Results: Your BMI value and category will be displayed
5. Reference Table: Use the built-in BMI categories table for interpretation

🧮 BMI Formula

The app uses the standard BMI formula:

BMI = weight (kg) / height (m)²

🔄 Unit Conversions

The app automatically handles these conversions:

• Height: feet → meters (× 0.3048), cm → meters (÷ 100)
• Weight: pounds → kg (× 0.453592), stones → kg (× 6.35029)