Using Swift For Android apps with Kotlin Multiplatform Mobile (KMM)

Swift for android

Embarking on the journey of mobile app development often leads to the crossroads of platform choice – iOS or Android? But what if you didn’t have to choose? 

The demand for efficient cross-platform solutions in mobile app development is rising. Kotlin Multiplatform Mobile (KMM) is a technology that allows developers to build apps that function seamlessly on both Android and iOS platforms. KMM’s unique compatibility with Swift, a programming language typically associated with iOS, makes it stand out. You might wonder if you can use Swift on Android with KMM. This blog explores the advantages, challenges, and potential of using Swift for Android app development with KMM.

What is KMM?

Kotlin Multiplatform Mobile (KMM) is a framework created by JetBrains, It is a feature of Kotlin that allows you to share code between Android and iOS platforms. Typically, you would write your business logic in Kotlin, which can be shared across both platforms and then implement platform-specific features using Swift for iOS and Kotlin for Android.

KMM’s Key Features:

  • Shared Codebase: With KMM, you write your app’s code once and use it on Android and iOS. For example, code to fetch weather data can be written in Kotlin and used on both platforms. This saves time and ensures consistent code.
  • Platform-Specific Modules: KMM allows you to add platform-specific components when needed. For a social media app, shared code can cover user profiles, authentication, and social feeds. Still, you can easily add Android-specific features like notifications or widgets for an improved Android experience.
  • Access to Native APIs: KMM lets you use Android and iOS native capabilities. In a navigation app, you can utilize Android’s location services and iOS’s MapKit for the best navigation experience. This access ensures your app leverages each platform’s unique strengths. Integrating these features helps you create top-notch apps for both Android and iOS users.

Why Choose KMM for Cross-Platform Development?

  • Efficiency: Develop once, apply changes once. This shared codebase approach streamlines development, saving time and effort.
  • Consistency: KMM ensures a consistent user experience on Android and iOS, as they share the same codebase.
  • Cost-Effectiveness: Time saved during development translates to cost savings, making KMM an attractive choice for businesses and startups.
  • Code Reusability: Code can be reused across platforms, minimizing redundancy and simplifying maintenance.

Shared Code’s Role:

KMM’s main principle is sharing code to use a single codebase for apps. It covers essential aspects like business logic, data models, and networking, serving as the foundation of the application. This shared code is written in Kotlin, known for its expressive, reliable, and modern features.

Swift for Android

Using Swift for Android development might not be a straightforward choice considering Swift is primarily a language for iOS development. However, there are scenarios where using Swift for Android or at least incorporating it into your Android development process, can be advantageous.

Why Swift for Android?

  • Shared Business Logic:
      • If you’re using Kotlin Multiplatform Mobile (KMM), you can share business logic between iOS and Android. While the shared code is in Kotlin, you can still use Swift for the iOS-specific parts. This means you can leverage the strengths of Swift on iOS while maintaining a shared codebase with Android.
  • Swift’s Popularity and Features:
      • Swift is a modern, fast, and type-safe language that has gained significant popularity. It has a clean syntax, is easier to read and write, and offers improved safety features, which can be appealing to developers who are already familiar with it from iOS development.
  • Developer Expertise:
      • If your development team is more experienced in Swift than Kotlin or Java, it might make sense to use Swift for shared logic to ensure a higher-quality codebase and to leverage existing expertise.
  • Cross-Platform Tools:
      • There are tools and frameworks like Google’s Flutter or React Native that allow for cross-platform development using a single codebase. While these don’t use Swift directly for Android, they represent a similar philosophy of cross-platform development where you could potentially use Swift for parts of your app.
  • Consistency Across Platforms:
      • For companies that maintain both iOS and Android apps, using Swift for both platforms can lead to more consistent implementation of features and business logic, easier maintenance, and potentially a smaller codebase.
  • Innovation and Experimentation:
      • Sometimes, the decision to use Swift or react native for Android can be driven by the desire to innovate or experiment with new architectures and processes. It can be a strategic move to stay ahead in technology adoption.
  • Swift for TensorFlow:
    • If you’re working on a project that involves machine learning, you might be interested in Swift for TensorFlow. While it’s a niche use case, it allows for the use of Swift in a cross-platform context that could include Android.

How to Use Swift for Android Apps with KMM?

Using Swift for Android app development with Kotlin Multiplatform Mobile (KMM) is an intelligent way to create cross-platform apps. It lets developers write shared code in Kotlin while taking advantage of Swift’s performance for Android. KMM simplifies the process and results in high-quality apps for both iOS and Android, reducing code duplication and maintenance.  

Kotlin Multiplatform Mobile (KMM) lets you create shared code for iOS and Android apps. While KMM primarily uses Kotlin, it also supports Swift for Android development. Let’s understand how to share Swift code across iOS and Android platforms.


Before you start using Swift in KMM for Android development, ensure you have the following:

  • Android Studio
  • Xcode
  • KMM plugin for Android Studio

Here are some steps to use Swift for Android apps with KMM after setting up your development environment.

Step 1: Create a New KMM Project

  • Open Android Studio.
  • Click on “New Project”.
  • Choose “Kotlin Multiplatform Mobile” from the list of templates.
  • Follow the wizard to set up your project, specify the name, and save the location.

Step 2: Configure the build.gradle.kts Files

Your KMM project will have two build.gradle.kts files: one for the entire project and one for the shared module.

Project-level build.gradle.kts

This file configures the build script dependencies for the entire project. You don’t need to change much here, but make sure you have the Kotlin Multiplatform plugin applied:

Replace YOUR_ANDROID_GRADLE_PLUGIN_VERSION and YOUR_KOTLIN_VERSION with the versions you’re using.

Step 3: Sync Your Project

After you’ve configured your build.gradle.kts files, click on the “Sync Now” link in the bar that appears at the top of the IDE to sync your project with the new settings.

Step 4: Write Shared Code

In the common main directory, you can write Kotlin code that will be shared between both Android and iOS.

Step 5: Write Platform-Specific Code

  • For Android, write your code in the androidMain directory.
  • For iOS, you will eventually use the generated framework in your Xcode project, where you can write Swift code.

Step 6: Build the Shared Framework

Run the build process to generate the .framework file for iOS:

  • Use the Gradle task packForXcode provided by the KMM plugin, or
  • Build from the command line with ./gradlew build.

Step 7: Integrate with Xcode

  • Open your Xcode project.
  • Add the generated .framework file to your Xcode project.
  • Ensure you can import and use the framework in your Swift files.

Step 8: Run Your Applications

  • Run the Android app using Android Studio.
  • Run the iOS app using Xcode.

Step 9: Maintain and Update

As you develop your app, you’ll maintain the shared Kotlin code and periodically recompile the shared framework for use in Xcode.

Optimizing and Refining Swift for Android

Optimizing Swift for Android in KMM may need extra work since it’s not Android’s primary language. Focus on performance, compatibility, and refining your Swift Android code for the best cross-platform functionality.

1. Performance Optimization:

  • Minimize Dependencies: Keep your Swift module’s dependencies to a minimum to avoid performance and size issues.
  • Memory Management: Pay attention to memory management, adapting it for Android’s constraints.
  • Threading and Concurrency: Align your Swift Android code threading model to ensure compatibility.

2. Compatibility with Android APIs:

  • Platform-Specific APIs: If your Swift code relies on iOS-specific APIs, find Android equivalents or implement platform-specific logic in Kotlin.
  • User Interface: Optimize your user interface elements to match Android’s design patterns for a native experience.

3. Testing and Debugging:

  • Emulators and Devices: Test your Swift Android code on various devices and emulators to ensure performance across different configurations.
  • Unit Testing: Implement unit tests to catch and fix any Android-specific issues early in development.

4. Refinement and Adaptation:

  • Iterative Development: Be ready to adapt your Swift code as you encounter issues and discover Android-specific requirements.
  • Community and Resources: Seek guidance from the Swift and Android development communities to learn from experienced cross-platform developers.

Optimizing Swift for Android within the KMM framework is essential for a successful cross-platform experience. Focus on performance, compatibility, testing, and refinement to maximize Swift while providing a seamless user experience on iOS and Android platforms.

Benefits of Using Swift for Android with KMM

The integration of Swift into Android development using KMM offers numerous benefits.

Code Reusability: 

By using KMM with Swift for Android, developers can write business logic and data models once in Swift, making it accessible on both Android and iOS platforms. This minimizes development time, maintains code consistency, and reduces the risk of bugs and inconsistencies.

Unified Development Team: 

KMM allows developers from both Android and iOS backgrounds to collaborate on the same codebase, eliminating the need for separate teams. This fosters better communication, collaboration, and a more efficient development process.

Reduced Maintenance: 

KMM simplifies maintenance by consolidating updates and bug fixes into a shared codebase, eliminating the need for making identical changes in two different languages. This results in significantly reduced maintenance efforts and a more stable application.

Improved Developer Productivity: 

Developers with Swift expertise can apply their skills to Android projects without the need to learn Kotlin or Java. This accelerates development and enhances developer productivity.

While Swift for Android with Kotlin Multiplatform Mobile (KMM) brings several advantages, it’s essential to acknowledge the challenges:

What are the challenges of using Swift for Android with KMM?

Learning Curve: 

Swift developers may find KMM easier. However, Android developers unfamiliar with Swift may face a learning curve. They must become proficient in Swift to work effectively within the shared codebase.

Limited UI Capabilities: 

KMM primarily targets non-UI code sharing. When dealing with complex or highly customized platform-specific user interfaces, you’ll still need to write platform-specific code for Android and iOS.

Platform-Specific Features: 

Not all platform-specific features or capabilities can seamlessly integrate into a KMM project. Some functionalities may necessitate platform-specific coding, adding complexity to the development process.

Ecosystem Limitations: 

The ecosystem of Swift on Android is less mature than it is on iOS. Consequently, you may not have access to the same libraries and tools for Android, requiring more custom development work.

Integration Challenges: 

Integrating Swift’s Android ecosystem can introduce compatibility and performance issues. Challenges arise when attempting to blend Android-specific libraries and tools with Swift code.

Debugging and Testing: 

Debugging and testing code of Swift on Android can be more intricate than in native Android languages. You should employ different tools and approaches to address issues effectively.

Community Support: 

The Swift for Android community is relatively smaller than communities surrounding other development languages. This can make it more challenging to find solutions to problems or receive the necessary support.

Maintenance of Swift Code: 

As the Swift language and ecosystem evolve, maintaining the code of Swift on Android may require vigilant adaptation to changes and updates, potentially consuming additional time and resources.


Kotlin Multiplatform Mobile (KMM) makes app development more accessible by allowing developers to use Swift for Android, saving time and effort. It eliminates the need for separate teams. 

Despite some challenges, the advantages of reusing code and unified development make KMM an intelligent choice. As technology progresses, more organizations will likely use KMM with Swift, resulting in better user experiences. 

In the ever-evolving world of mobile development, exploring the potential of Swift on Android with KMM is a forward-looking strategy, and it is becoming an invaluable asset for companies like VisionX that aim to deliver exceptional and unified app experiences across different platforms. This innovative approach reflects the vision and adaptability of companies prioritizing efficiency and excellence in mobile app development.

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