Android Basics

Android is open-source and built on the Linux kernel, which makes it flexible, secure, and highly customizable.
The Android mobile ecosystem includes:
Android OS
Mobile devices (phones, tablets, TVs, wearables)
Google Play Store
App developers and users
Supporting tools and services (APIs, SDKs, cloud services)

Understanding this ecosystem helps developers build apps that are scalable, secure, and compatible across many devices.

Android Studio Setup

Android Studio is the official Integrated Development Environment (IDE) for Android app development. It provides all the tools needed to design, develop, test, and debug Android applications.

Key features of Android Studio:
Code editor with smart suggestions
Visual layout designer
Built-in emulator
Gradle build system
Debugging and profiling tools

Basic setup steps:
Download Android Studio from the official Android website
Install required SDK components
Configure an Android Emulator or connect a physical device
Create your first Android project

Once set up, Android Studio becomes the main workspace for building Android apps.

Android Project Structure Explained

An Android project follows a well-defined structure to keep code organized and maintainable.

Important folders and files:
manifests/
Contains AndroidManifest.xml, which defines app permissions, components, and configuration.

java/ or kotlin/
Contains source code for Activities, Fragments, ViewModels, and logic.

res/
Holds app resources like layouts, images, colors, strings, and styles.

Gradle Scripts
Manage dependencies, build configurations, and app versions.

Understanding the project structure is essential for writing clean code and managing large applications.

APK vs AAB (Android App Bundle)

Android apps can be packaged in two formats:

APK (Android Package)
Traditional app installation file
Contains all resources for all device types
Larger file size

AAB (Android App Bundle)
Modern publishing format recommended by Google
Google Play generates optimized APKs for each device
Smaller download size
Better performance and delivery

Google Play now requires AAB for new app submissions, making it the preferred format for developers.

Android App Lifecycle

The Android App Lifecycle defines how an app behaves when it starts, runs, pauses, stops, and closes. Managing lifecycle events correctly ensures better performance and user experience.

Key lifecycle states:
onCreate() – App is created and initialized
onStart() – App becomes visible
onResume() – App is in the foreground and interactive
onPause() – App partially visible
onStop() – App no longer visible
onDestroy() – App is destroyed and cleaned up

Understanding the lifecycle helps developers:
Save user data properly
Handle screen rotations
Optimize memory usage
Avoid app crashes