Android App Development Basics (2025 Guide)

Android development is easiest to learn when you understand the core building blocks: how the project is built (Gradle), how UI is rendered (Jetpack Compose), how state is managed, and how your app interacts with the system (permissions, storage, networking).

This guide focuses on modern Android in 2025: Kotlin-first development and Compose-first UI, with pragmatic architecture that helps you ship.

1. What Android Development Covers in 2025

• Language: Kotlin (typical default for new apps).
• UI: Jetpack Compose.
• State: ViewModel + reactive streams (Flow).
• Data: Room / DataStore / files.
• Networking: HTTP APIs with robust error handling.
• Build & release: Gradle, signing, app bundles.

2. Tools & Setup: Android Studio, SDK, Emulator

A minimal setup looks like:

• Android Studio: IDE + emulator tools.
• Android SDK: platform tools, build tools, images.
• Emulator: fast iteration; also test on a real phone.
• Git: version control from day one.

3. Project Structure: Modules, Gradle, Manifest

A typical Android project includes:

• app module: your app code and resources.
• Gradle files: dependencies, build variants, configs.
• AndroidManifest.xml: app metadata and permissions.
• resources: strings, icons, themes.

4. Kotlin Basics You Need for Android

• Null safety: nullable types and safe calls.
• Coroutines: async work without blocking UI.
• Data classes: models for API responses and UI state.
• Sealed classes: UI states (Loading/Success/Error).

// Common UI state pattern (conceptual)
sealed class UiState {
  object Loading : UiState()
  data class Success(val data: List<Item>) : UiState()
  data class Error(val message: String) : UiState()
}

5. Jetpack Compose UI Basics: Composables and Layout

Compose is a declarative UI toolkit: you describe what the UI should look like for a given state, and Compose re-renders as state changes.

• Composable functions: building blocks of UI.
• Layouts: Column, Row, Box, LazyColumn.
• Material components: buttons, inputs, cards.
• Preview: quick UI iteration inside Android Studio.

6. State and UI Logic: ViewModel, Flows, and Events

A practical beginner boundary:

• UI layer: renders state, sends events (button clicks).
• ViewModel: holds state, runs business logic.
• Repository: talks to network/storage.

7. Navigation: Screens, Back Stack, and Deep Links

Navigation is about defining screens and moving between them:

• Routes: names for destinations.
• Back stack: how the user navigates back.
• Arguments: pass IDs, not whole objects.
• Deep links: optional later step for shareable URLs.

8. Permissions and Privacy (What to request and when)

Request the minimum permissions you need, at the moment they’re needed:

• Explain: show why you need the permission.
• Degrade gracefully: app still works without it (if possible).
• Store review: unnecessary permissions can be a red flag.

9. Storage Basics: DataStore, Room, Files

• DataStore: small preferences/settings.
• Room: structured local database.
• Files: app-specific cache and storage.

10. Networking Basics: HTTP, Retrofit, and Error Handling

For most beginner apps, you need:

• HTTP client: request/response.
• JSON parsing: map responses to Kotlin data classes.
• Error handling: timeouts, offline mode, API errors.
• Loading states: predictable UI during requests.

Networking checklist
- Show loading state
- Handle offline and timeout
- Show a friendly error + retry
- Log details for debugging (not for users)

11. Testing Basics: Unit, UI, and Smoke Tests

• Unit tests: ViewModel and business logic.
• UI tests: critical flows (login, create item, etc.).
• Smoke tests: install and click through key screens.

12. Release Checklist: Signing, App Bundle, Store Assets

Before release:

• Versioning: bump versionCode/versionName.
• Signing: create and store keystore securely.
• Build: generate a release App Bundle (AAB).
• Assets: icon, screenshots, description.
• Policy: privacy disclosures match app behavior.
• Stability: crash test on a real device.

13. FAQ: Android Basics

Is Kotlin enough to build real Android apps?

Yes. Kotlin is widely used for production Android apps and integrates well with modern Android libraries and tooling.

Should I learn Compose first?

If you are starting in 2025, Compose is a practical default. You can learn XML layouts later if you need to work on legacy projects.

Do I need MVVM for a first app?

You don’t need heavy architecture, but separating UI from state logic (ViewModel) keeps projects maintainable even at small sizes.

How do I test on multiple screen sizes?

Use emulator profiles (phones/tablets) and Compose previews. Still verify the main flows on at least one real device.

What is the easiest first app to build?

A notes or checklist app is a great first project: multiple screens, local storage, and simple UI state.

Key Android terms (quick glossary)

Android Studio

The official IDE for Android development, including emulator and build tools.

Kotlin

A modern JVM language commonly used for Android development.

Jetpack Compose

A declarative UI toolkit for building Android interfaces with Kotlin.

ViewModel

A state holder that survives configuration changes and manages UI logic.

Gradle

The build system used to manage dependencies and produce app builds.

Manifest

AndroidManifest.xml: declares app components, permissions, and metadata.

Room

A persistence library for local SQLite databases with Kotlin-friendly APIs.

DataStore

A modern Android storage solution for preferences and small key-value data.