Multiplatform Development on Kotlin Programming Language

Introduction

In today’s fast-paced software development landscape, the need for efficient, cross-platform solutions has become more pronounced than ever. Businesses and developers are increasingly looking for ways to streamline development processes, reduce costs, and maximize code reusability while delivering high-quality applications across various platforms. One of the most effective solutions to achieve this is Kotlin Multiplatform (KMP), a feature of the Kotlin programming language that enables developers to write shared code for multiple platforms while maintaining platform-specific implementations where necessary.

In this blog post, we will explore the concept of multiplatform development in Kotlin, its benefits, use cases, architecture, and how to get started with Kotlin Multiplatform.

What is Kotlin Multiplatform?

Kotlin Multiplatform (KMP) is a feature introduced by JetBrains that allows developers to write code once and run it on multiple platforms, including Android, iOS, Windows, macOS, Linux, Web, and even embedded systems. Unlike traditional cross-platform frameworks that rely on a single codebase and rendering engine (such as Flutter or React Native), KMP enables sharing business logic and data layer code while keeping UI implementations native.

Key Features of Kotlin Multiplatform

• Code Reusability: Share common logic across multiple platforms while still allowing platform-specific customization.
• Interoperability: Seamlessly integrate with existing platform-specific code in Java, Swift, Objective-C, and JavaScript.
• Flexibility: Unlike full cross-platform frameworks, KMP does not enforce a specific UI rendering system, allowing developers to retain native UI experiences.
• Scalability: Supports multiple platforms, including JVM, JavaScript, Native, and WebAssembly.
• Tooling Support: Fully supported by JetBrains’ IntelliJ IDEA and Android Studio, providing robust debugging and development tools.

Benefits of Using Kotlin Multiplatform

1. Increased Code Efficiency

   • KMP allows developers to write common business logic once and share it across platforms, reducing redundant coding efforts.

2. Cost Reduction

   • By reusing a significant portion of the codebase, businesses can reduce development time and costs associated with maintaining separate codebases for different platforms.

3. Better Maintainability

   • With a single shared codebase, bug fixes and feature updates can be implemented faster and with fewer inconsistencies across platforms.

4. Native Performance

   • Unlike other cross-platform solutions that rely on web views or intermediary layers, KMP provides direct access to platform APIs, ensuring optimal performance.

5. Seamless Integration with Existing Codebases

   • Developers can incrementally adopt KMP in existing projects without the need to rewrite entire applications.

Understanding Kotlin Multiplatform Architecture

Kotlin Multiplatform follows a modular architecture with three main layers:

1. Common Code Module

• This module contains shared logic, such as business rules, API calls, database handling, and networking.
• Written in pure Kotlin, this module is compiled for different platforms using Kotlin’s compiler.

2. Platform-Specific Implementations

• While the common module provides the core functionality, certain platform-specific features (like UI, file handling, or native APIs) need separate implementations.
• KMP allows developers to use expect and actual keywords to define and implement platform-specific code as needed.

3. Application Modules (Android, iOS, Web, etc.)

• These modules contain platform-specific UI and additional customization, ensuring the best user experience on each platform.

Setting Up Kotlin Multiplatform Project

To get started with Kotlin Multiplatform, follow these steps:

1. Install the Necessary Tools

Ensure you have:

• Kotlin 1.5+ installed
• Android Studio or IntelliJ IDEA with the Kotlin plugin enabled
• Gradle 7.0+

2. Create a New Kotlin Multiplatform Project

You can create a new project using IntelliJ IDEA or Android Studio:

1. Open IntelliJ IDEA or Android Studio.
2. Select New Project > Kotlin Multiplatform Mobile.
3. Choose iOS & Android template.
4. Configure project settings and click Finish.

3. Project Structure Overview

A typical Kotlin Multiplatform project has the following structure:

myKMPProject/
├── shared/              # Common shared code
│   ├── src/commonMain/  # Shared logic
│   ├── src/androidMain/ # Android-specific code
│   ├── src/iosMain/     # iOS-specific code
│   ├── build.gradle.kts # Build configuration
│
├── androidApp/         # Android application module
│   ├── src/main/
│   ├── build.gradle.kts
│
├── iosApp/             # iOS application module
│   ├── iosApp.xcodeproj/
│   ├── build.gradle.kts
│
├── settings.gradle.kts
└── build.gradle.kts

4. Writing Shared Code

Inside the shared/src/commonMain directory, you can define shared logic:

expect class Platform() {
    val name: String
}

For Android (shared/src/androidMain):

actual class Platform() {
    actual val name: String = "Android"
}

For iOS (shared/src/iosMain):

actual class Platform() {
    actual val name: String = "iOS"
}

5. Building and Running the Application

• Run the Android app using Android Studio.
• Open the iosApp.xcodeproj file in Xcode and run it on an iOS simulator.

Real-World Use Cases of Kotlin Multiplatform

1. Shared Business Logic

   • Ideal for applications that require a shared backend processing layer, such as authentication, networking, and caching.

2. Cross-Platform SDKs

   • Companies can create SDKs that work across multiple platforms, reducing development effort for clients.

3. Multiplatform Game Development

   • Game developers can use KMP to write game logic once while keeping platform-specific graphics rendering.

4. Enterprise Applications

   • Organizations building internal tools can use KMP to maintain a single codebase while deploying on multiple platforms.

Conclusion

Kotlin Multiplatform offers an innovative and pragmatic approach to cross-platform development. By enabling code reuse while preserving native performance and flexibility, KMP strikes a perfect balance between productivity and platform-specific optimizations. With strong tooling support and a growing community, it is poised to become a leading solution for modern multiplatform development.

If you are a developer looking to reduce code duplication and improve maintainability while still providing the best user experience, Kotlin Multiplatform is definitely worth considering.

Are you excited to try Kotlin Multiplatform? Let us know your thoughts in the comments below!