Android App Development Guide

Setting up the Android App Development Environment

Requirements

To develop Android apps, you’ll need:

• Hardware: At least 8GB RAM, Intel Core i5 or equivalent, SSD for better performance.
• Software: Android Studio, JDK 8 or higher, Android SDK tools.

Even though you can use the Android emulator provided in the Android development tools to test your mobile app, it’s recommended that you also have access to an Android mobile device.

Download and Installation

• Download Android Studio from the official website.
• Install Android Studio, follow the setup wizard, and ensure the necessary SDKs are installed.
• Configure the SDK Manager to download SDK tools and system images for emulators.
• Set up the AVD (Android Virtual Device) for testing or connect a physical Android device via USB (enable Developer Mode).

Project Setup & Understanding Gradle

• Start a new project in Android Studio. Choose the project type, set the app name, package, and target API level.
• Understand the project structure:
  • src/: Contains Java/Kotlin code.
  • res/: Stores resources like XML layouts, images, and strings.
  • AndroidManifest.xml: Declares app configuration, permissions, and components.
• Gradle is the build automation tool. The key files:
  • build.gradle (Project level): Dependencies and configurations shared across modules.
  • build.gradle (Module level): Defines specific app dependencies, configurations, and build types.

Understanding Android Architecture

Before diving into how Android applications are built, we recommend you first check out our guide on Mobile App Architectures. This will give you a global understanding of the different architectures you can use to build your app, which can enhance your knowledge as an Android developer. Once you’ve grasped the basics, it’s time to explore how you can implement the chosen architecture using Android components.

Android apps made up of four core components:

1. Activities: UI components that represent a single screen. An activity contains views (buttons, text, images).
2. Fragments: Modular UI components within an activity. They allow dynamic, reusable UIs.
3. Services: Handle background tasks like fetching data or playing music, without direct user interaction.
4. Broadcast Receivers: Allow apps to respond to broadcast messages, like battery low or Wi-Fi changes.
5. Content Providers: Manage shared data, enabling inter-app communication using SQLite, Room, or external storage.

You can use any combination of these components to model your requirements and business logic.

One of the most important components is Activities, so it’s crucial to understand the basic lifecycle of an Android activity. The key methods are:

• onCreate(): Initializes the activity.
• onStart(): Activity becomes visible.
• onResume(): The activity is in the foreground and the user can interact with it.
• onPause(): Activity loses focus (e.g., another app appears in the foreground).
• onStop(): Activity is no longer visible.
• onDestroy(): Activity is finishing or being destroyed by the system.

Managing the lifecycle efficiently is key to saving the state, managing resources, avoiding memory leaks and keeping you are app responsive to avoid any ANR (App Not Responsive) problem.

Coding in Kotlin

Previously, most Android developers used Java for development, as it was the original language for Android. However, Kotlin has recently become the preferred language for Android due to its modern syntax and safety features. You can explore the main differences between the two languages in our Kotlin vs Java article.

Here you can see the basic of Kotlin language:

1. Basic Syntax:
   • Variables: val for read-only and var for mutable variables.
   • Control flow: Standard conditional and looping constructs like if, when, for, and while.
2. Object-Oriented Programming:
   • Classes: Define objects with properties and methods. Kotlin supports single inheritance and interfaces.
   • Null Safety: Kotlin’s type system ensures that null values are explicitly handled with nullable types (?).
3. Functions: First-class functions, lambda expressions, and higher-order functions simplify code.
4. Extensions: Extend existing classes with new functionality without altering the original class definition.

Once you’ve mastered the basics, you can explore more advanced Kotlin topics:

• As within any programming language, taking the most of arrays and also learn about all Kotlin collections is a must and something you will be dealing on a daily basis, so this might be your first step.
• Discover how to use Kotlin generics to build flexible, reusable code.
• Kotlin enums can also be really helpful to improve the clarity of your code
• Dealing with dates in Kotlin can be tricky, so learning how Kotlin handles dates can be helpful when working with customers in different time zones.

Advanced Android Topics

Android Jetpack

Once you’ve learned the Kotlin basics, you can move on to more advanced topics that will help you become a senior Android developer. One of the most important areas to explore is Android Jetpack, a set of pre-built libraries and components that make building robust apps easier and faster. Jetpack includes:

1. ViewModel: Manages UI-related data lifecycle-aware, avoiding memory leaks.
2. LiveData: Observable data holder that updates the UI when the data changes.
3. Navigation: Simplifies fragment navigation and back stack management.
4. Room: Provides an abstraction layer over SQLite for easier data persistence.
5. WorkManager: Handles background tasks that need guaranteed execution.

Android Networking

Gone are the days when apps were isolated from the external world. Today, almost all apps need to communicate with a server to fetch dynamic content, enabling users to stay connected. To do this, your app will need to communicate with a server using a REST API or GraphQL API. If you’re building a new system from scratch, GraphQL might be the best option, as it allows for more efficient, data-driven applications.

Android Asynchronous Programming

When writing an Android application, it’s essential to keep it responsive to meet user expectations and avoid ANR (App Not Responding) errors, which can frustrate users. To achieve a smooth, responsive app, you can take advantage of Kotlin coroutines. These allow you to write asynchronous code with ease and run background tasks efficiently.

Android App Testing, QA and distribution

App Testing & QA Best Practices

One of the final, but crucial, steps is learning how to publish your app efficiently and reliably. To ensure a high-quality release, you must test your app thoroughly and be prepared to provide customer support, regardless of the user’s device, location, or edge cases. It’s also important to have a solid error-handling mechanism to address any issues that arise during the app’s operation.

As an Android developer, writing proper Kotlin unit tests can make the difference between a buggy app and a well-functioning one. Additionally, establishing a robust development process will boost your confidence when releasing your app, significantly easing the process. Automating as much as possible — from automating builds to utilizing automated testing tools — can save both time and money.

Remember, bugs are inevitable in the life of a developer. While it’s expected that your app will have some glitches, having a solid plan for resolving them is crucial. Be ready to debug your app and learn how ADB (Android Debug Bridge) can assist you in the debugging process. Additionally, for scenarios where direct debugging on a physical device isn’t possible, learn how to obtain logs from customer devices to help identify and fix issues.

App Distribution

Effective app distribution is vital in Android app development, ensuring your app reaches its audience through platforms like Google Play Store, third-party stores, or direct downloads. To succeed, optimize listings with keywords, visuals, and descriptions for visibility and downloads. Using analytics tools will provide insights to enhance user experience and retention. A well-executed distribution strategy is crucial for an Android app to achieve its potential and connect with its target users.

These are the basic steps you need to publish a mobile app in the Google app store:

• Building Signed APK: Configure release builds by adding a keystore and signing configuration in the build.gradle.
• Google Play Store:
  • Create a developer account and upload the APK via Google Play Console.
  • Ensure your app is ready with proper assets (icons, descriptions) and compliance with Play Store policies.

App Monetization

Monetizing and marketing your mobile application is one of the biggest challenges any app developer will face. To reach your customers, you need a marketing plan in place to promote your app, similar to marketing any product but with specific constraints since your app will be published in an app store. Learn everything you can about ASO (App Store Optimization) and how to promote your app efficiently.

On the monetization side, when building your Android mobile app, consider using one of the following commonly used strategies:

• In-App Advertising: Use platforms like AdMob to display ads and earn from impressions or clicks.
• Freemium Model: Offer a free app with optional in-app purchases for advanced features or removing ads.
• Subscriptions: Provide premium content or services through recurring payments.
• One-time Purchase: Charge users a one-time fee to download your app.
• Sponsorships: Partner with brands for sponsored content or features.
• Affiliate Marketing: Promote products within your app and earn commissions.

Choose the strategy that best fits your app and target audience.