Add Kotlin Multiplatform to an existing project

To create a Kotlin Multiplatform (KMP) module within your Android project, use the Kotlin Multiplatform Shared Module template, available in Android Studio Meerkat and Android Gradle Plugin version 8.8.0 and higher.

The module template automates the creation of a new module with the minimum configuration targeting Android and iOS platforms.

Set up the shared KMP module

To create a shared KMP module, follow these steps:

  1. Select File > New > New Module
  2. Select the Kotlin Multiplatform Shared Module template in the Templates panel:
Creating a new KMP Module
Figure 1. Creating a new KMP Module

The fields in the template are the following:

  • Module name – defines the Gradle module name, as well as the iOS framework name (can be changed later)
  • Package name – defines the package name for files in this module
    1. Click Finish and allow Gradle to sync with the project. You might also be prompted to add the newly created module files to source control.

Once complete, the Android Studio Project View shows the new shared module along with a sourceset for each platform.

Project view showing new shared modules
Figure 2. Project view showing new shared modules

The module wizard doesn't add the newly created module as a dependency to any existing module. As a next step, you need to link the shared module to one of your existing Gradle modules similarly to other Android dependencies

dependencies {
    ...
    implementation(project(":shared"))
}

Once enabled, you can access code as usual. From the Android app, you're able to access code that is available either in androidMain or in commonMain.

For more information on Kotlin Multiplatform project structure, see the basics of Kotlin Multiplatform project structure

Set up the shared module to the iOS app

Swift can't use Kotlin modules directly and requires a compiled binary framework to be produced.

The new module template in Android Studio configures the shared module to produce a framework for each of the iOS architectures. You can find the following code in the shared module's build.gradle.kts file:

val xcfName = "sharedKit"

iosX64 {
  binaries.framework {
    baseName = xcfName
  }
}

iosArm64 {
  binaries.framework {
    baseName = xcfName
  }
}

iosSimulatorArm64 {
  binaries.framework {
    baseName = xcfName
  }
}

See Hierarchical project structure for information on defining other architecture types.

To enable access to the shared code from the iOS project, add a script phase to generate the Kotlin framework before compiling the Swift sources:

  1. Right-click the file in the Android Studio and select Open In and Open in Associated Application. This will open the iOS app in Xcode.
Open in Associated Application
Figure 3. Open in Associated Application
  1. Open the project settings by double-clicking the project name in the project navigator
Xcode project settings dialog
Figure 4. Xcode project settings dialog
  1. Change the default Run Script name to Compile Kotlin Framework to better identify what this phase does. Double-click the Run Script title to edit it.
  2. Expand the build phase, and in the Shell text field, enter the following script code:
Adding a new run script build phase
Figure 5. Run script build phase

  1. Drag the Run Script phase before the Compile Sources phase.

    Run script build phase before compile sources
    Figure 6. Run script build phase before compile sources

  2. Build the project in Xcode by clicking ⌘B or navigating to the Product menu and selecting Build.

When the build succeeds, you'll see the following icon.

Build successful shown in Xcode
Figure 7. Build successful

Access the shared code in the iOS app

To verify that the iOS app can successfully access code from the shared module, do the following:

  1. In the iOS project, open the ContentView.swift file at: Sources/View/ContentView.swift
  2. Add import sharedKit at the top of the file.
  3. Modify the Text view to include the Platform_iosKt.platform() information in the displayed string as follows:

This update checks whether the Fruitties app can call the platform() function from the shared module, which should return "iOS" when running on the iOS platform.

Xcode simulator running the iOS app
Figure 8. Xcode simulator running the iOS app

Additional Resources

If you're new to KMP development, see the official KMP documentation for more guides. If you're new to iOS development, see Swift Basics documentation..