Android Notes Help

Fundamentals

Android is an open-source operating system primarily designed for mobile devices such as smartphones and tablets.

It is based on the Linux kernel and developed by a consortium of developers known as the Open Handset Alliance, led by Google.

Gradle

Android Studio IDE uses Gradle as its build system.

Gradle is a powerful and flexible build automation tool used in software development, particularly in the Java and Android ecosystems.

It is designed to manage the build lifecycle of projects, automate the compilation and packaging processes, and handle dependencies efficiently.

Gradle is the tool working behind the scenes to compile and package your app.

SDK

Software Development Kit is a pile of tools, libraries, and APIs that let you build, run, test, and debug Android apps.

What it essentially contains

  1. Android APIs: These are the classes you actually code against.

    • Activity, Service, BroadcastReceiver, ContentProvider

    • UI stuff like View, RecyclerView, ConstraintLayout

    • System services: camera, location, sensors, storage, network, etc.

  2. SDK Tools: Command-line tools.

    • adb (Android Debug Bridge) for installing apps, logs, debugging

    • sdkmanager to download SDK components

    • avdmanager for emulators

  3. Platform Tools: Low-level tools tied closely to the OS.

    • adb, fastboot

    • Used for device communication and system-level operations

  4. Build Tools: Used during compilation and packaging.

    • aapt / aapt2 (resource packaging)

    • d8 / r8 (bytecode → dex, shrinking, obfuscation)

    • zipalign, apksigner

You rarely touch these directly because Gradle automates this.

  1. Android Platforms

    • Example: Android 13 (API 33), Android 14 (API 34)

    • Each platform = specific APIs + system behavior

  2. Emulator & System Images: Virtual Android devices.

    • Different API levels

    • Different hardware profiles

What Android SDK is NOT

Not Android Studio (that’s the IDE)

Not Gradle (that’s the build system)

Not the Android OS itself

Android SDK is a toolbox that helps you build Android apps which use the Android OS framework components like Activity, Service, BroadcastReceiver, etc.

Why SDK Exists

  • Without the SDK:

    • You wouldn’t know which methods exist

    • You couldn’t compile your app

    • You’d be guessing system behavior and breaking apps across versions

The SDK is basically a contract: “If you call this method, the OS promises to do this.”

  • One-line mental model:

    • SDK = tools + API contracts

    • OS = actual implementation + execution

Last modified: 05 February 2026
App Components