Kotlin Multiplatform Development Help

Create your multiplatform project

Here, you'll learn how to create and run your first Compose Multiplatform application using the Kotlin Multiplatform web wizard and Android Studio.

With the Compose Multiplatform UI framework, you can push the code-sharing capabilities of Kotlin Multiplatform beyond application logic. You can implement the user interface once and then use it for all the platforms supported by Compose Multiplatform.

In this tutorial, you will build a sample application that runs on Android, iOS, desktop, and web. To create a user interface, you will use the Compose Multiplatform framework and learn about its basics: composable functions, themes, layouts, events, and modifiers.

Things to keep in mind for this tutorial:

  • No previous experience with Compose Multiplatform, Android, or iOS is required. We do recommend that you become familiar with the fundamentals of Kotlin before starting.

  • To complete this tutorial, you'll only need Android Studio. It allows you to try multiplatform development on Android and desktop. For iOS, you'll need a macOS machine with Xcode installed. This is a general limitation of iOS development.

  • If you wish, you can limit your choice to the specific platforms you're interested in and omit the others.

Set up an environment

Check out the article about setting up an environment for Kotlin Multiplatform development, if you haven't already. Make sure that you have:

  • Installed the Kotlin Multiplatform plugin for Android Studio.

  • Launched Xcode at least once and accepted the terms of use if you plan to build iOS apps.

  • Run Kdoctor to check for any issues in the setup.

The following instructions assume that you have all software necessary for the platforms you're aiming at.

Create a project using the wizard

To begin, create a sample project. This is best achieved with the Kotlin Multiplatform web wizard:

  1. Open the Kotlin Multiplatform wizard.

  2. On the New project tab, change the project name to "ComposeDemo" and the project ID to "compose.project.demo".

  3. Select the Android, Desktop, and Web options.

  4. If you're using a Mac, select iOS as well. Make sure that the Share UI option is selected.

  5. Click the Download button and unpack the resulting archive.

Kotlin Multiplatform wizard

Examine the project structure

  1. Launch Android Studio.

  2. On the Welcome screen, click Open, or select File | Open in the editor.

  3. Navigate to the unpacked "ComposeDemo" folder and then click Open.

    Android Studio detects that the folder contains a Gradle build file and opens the folder as a new project.

    If you didn't select iOS in the wizard, you won't have the folders whose names begin with "ios" or "apple".

  4. The default view in Android Studio is optimized for Android development. To see the full file structure of the project, which is more convenient for multiplatform development, switch the view from Android to Project:

    Select the Project view

The project contains two modules:

  • composeApp is a Kotlin module that contains the logic shared among the Android, desktop, iOS, and web applications – the code you use for all the platforms. It uses Gradle as the build system that helps you automate your build process.

  • iosApp is an Xcode project that builds into an iOS application. It depends on and uses the shared module as an iOS framework.

    Compose Multiplatform project structure

The composeApp module consists of the following source sets: androidMain, commonMain, desktopMain, iosMain, and wasmJsMain. A source set is a Gradle concept for a number of files logically grouped together, where each group has its own dependencies. In Kotlin Multiplatform, different source sets can target different platforms.

The commonMain source set uses the common Kotlin code, and platform source sets use Kotlin code specific to each target. Kotlin/JVM is used for androidMain and desktopMain. Kotlin/Native is used for iosMain. On the other hand, Kotlin/Wasm is used for wasmJsMain.

When the shared module is built into an Android library, common Kotlin code gets treated as Kotlin/JVM. When it is built into an iOS framework, common Kotlin code gets treated as Kotlin/Native. When the shared module is built into a web app, common Kotlin code gets treated as Kotlin/Wasm.

Common Kotlin, Kotlin/JVM, and Kotlin/Native

In general, write your implementation as common code whenever possible instead of duplicating functionality in platform-specific source sets.

In the composeApp/src/commonMain/kotlin directory, open the App.kt file. It contains the App() function, which implements a minimalistic but complete Compose Multiplatform UI:

@Composable @Preview fun App() { MaterialTheme { var showContent by remember { mutableStateOf(false) } Column(Modifier.fillMaxWidth(), horizontalAlignment = Alignment.CenterHorizontally) { Button(onClick = { showContent = !showContent }) { Text("Click me!") } AnimatedVisibility(showContent) { val greeting = remember { Greeting().greet() } Column(Modifier.fillMaxWidth(), horizontalAlignment = Alignment.CenterHorizontally) { Image(painterResource(Res.drawable.compose_multiplatform), null) Text("Compose: $greeting") } } } } }

Let's run the application on all supported platforms.

Run your application

You can run the application on Android, iOS, desktop, and web. You don't have to run the applications in any particular order, so start with whichever platform you are most familiar with.

Run your application on Android

  1. Create an Android virtual device.

  2. In the list of run configurations, select composeApp.

  3. Choose your Android virtual device and then click Run: Android Studio will start the selected virtual device if it is powered down, and run the app.

Run the Compose Multiplatform app on Android
First Compose Multiplatform app on Android

Run on a different Android simulated device

Learn how to configure the Android Emulator and run your application on a different simulated device.

Run on a real Android device

Learn how to configure and connect a hardware device and run your application on it.

Run your application on iOS

  1. Launch Xcode in a separate window to complete the initial setup. If it's the first time you launch Xcode, you may also need to accept its license terms and allow it to perform some necessary initial tasks.

  2. In Android Studio, select iosApp in the list of run configurations and click Run. By default, the run configuration will start a simulated device available in Xcode and run the app there. If you don't have an available iOS configuration in the list, add a new run configuration.

Run the Compose Multiplatform app on iOS
First Compose Multiplatform app on iOS

Run on a new iOS simulated device

If you want to run your application on a simulated device, you can add a new run configuration.

  1. In the list of run configurations, click Edit Configurations.

    Edit run configurations

  2. Click the + button above the list of configurations and then select iOS Application.

    New run configuration for iOS application

  3. Name your configuration.

  4. Select the Xcode project file. To do so, navigate to your project, for example, KotlinMultiplatformSandbox, open the iosApp folder, and then select the .xcodeproj file.

  5. In the Execution target list, select a simulated device and then click OK.

    New run configuration with iOS simulator

  6. Click Run to run your application on the new simulated device.

Run on a real iOS device

You can run your multiplatform application on a real iOS device. Before you start, you'll need to set the Team ID associated with your Apple ID.

Set your Team ID

To set the Team ID in your project, you can either use the KDoctor tool in Android Studio or choose your team in Xcode.

For KDoctor:

  1. In Android Studio, run the following command in the terminal:

    kdoctor --team-ids

    KDoctor will list all Team IDs currently configured on your system, for example:

    3ABC246XYZ (Max Sample) ZABCW6SXYZ (SampleTech Inc.)

  2. In Android Studio, open the iosApp/Configuration/Config.xcconfig and specify your Team ID.

Alternatively, choose the team in Xcode:

  1. Go to Xcode and select Open a project or file.

  2. Navigate to the iosApp/iosApp.xcworkspace file of your project.

  3. In the left-hand menu, select iosApp.

  4. Navigate to Signing & Capabilities.

  5. In the Team list, select your team.

    If you haven't set up your team yet, use the Add an Account option in the Team list and follow Xcode instructions.

  6. Make sure that the Bundle Identifier is unique and the Signing Certificate is successfully assigned.

Run the app

Connect your iPhone with a cable. If you already have the device registered in Xcode, Android Studio should show it in the list of run configurations. Run the corresponding iosApp configuration.

If you haven't registered your iPhone in Xcode yet, follow Apple recommendations. In short, you should:

  1. Connect your iPhone with a cable.

  2. On your iPhone, enable the developer mode in Settings | Privacy & Security.

  3. In Xcode, go to the top menu and choose Window | Devices and Simulators.

  4. Click on the plus sign. Select your connected iPhone and click Add.

  5. Sign in with your Apple ID to enable development capabilities on the device.

  6. Follow the on-screen instructions to complete the pairing process.

Once you've registered your iPhone in Xcode, create a new run configuration in Android Studio and select your device in the Execution target list. Run the corresponding iosApp configuration.

Run your application on desktop

You can create a run configuration for running the desktop application as follows:

  1. Select Run | Edit Configurations from the main menu.

  2. Click the plus button and choose Gradle from the dropdown list.

  3. In the Tasks and arguments field, paste this command:

    composeApp:run

  4. Click OK.

Now, you can use this configuration to run the desktop app in its own OS window:

Run the Compose Multiplatform app on desktop
First Compose Multiplatform app on desktop

Run your web application

Create a run configuration to run the web application:

  1. Select Run | Edit Configurations from the main menu.

  2. Click the plus button and choose Gradle from the dropdown list.

  3. In the Tasks and arguments field, paste this command:

    wasmJsBrowserRun -t --quiet

  4. Click OK.

Now, you can use this configuration to run the web app:

Run the Compose Multiplatform app on desktop

The web application opens automatically in your browser. Alternatively, you can type the following URL in your browser when the run is finished:

http://localhost:8080/
Compose web application

Next step

In the next part of the tutorial, you'll learn how to implement composable functions and launch your application on each platform.

Proceed to the next part

Get help

Last modified: 04 October 2024
Wrap up your projectExplore composable code