Compose Multiplatform Mobile Library

This is a template for a Compose Multiplatform library targeting Android and iOS. It is built on top of the Compose Multiplatform IOS and Android Template and contains the following changes:

• Add a lib module for the shared library code.
• Move the androidApp and iosApp modules to the samples folder.
• Apply the org.jetbrains.dokka plugin to generate documentation for the library code.
• Apply the com.vanniktech.maven.publish plugin to streamline the process of publishing a library.
• Apply the org.jlleitschuh.gradle.ktlint plugin to enforce the code style and set up the git hooks to fix the code style before committing automatically.
• Set up the CI pipeline to build the project, check the code style, and publish the documentation.

Note: If you also want to make your library support Desktop target, please use this template https://github.com/KevinnZou/compose-multiplatform-library-template

Maven Publish

This template applies the com.vanniktech.maven.publish plugin to streamline the process of publishing a library.

Configuring

To publish your library properly, you need to configure the necessary information in mavenPublishing block in build.gradle.kts

mavenPublishing {
    // publishToMavenCentral(SonatypeHost.DEFAULT)
    // or when publishing to https://s01.oss.sonatype.org
    publishToMavenCentral(SonatypeHost.S01, automaticRelease = true)
    signAllPublications()
    coordinates("com.example.mylibrary", "mylibrary-runtime", "1.0.0")

    pom {
        name.set(project.name)
        description.set("A description of what my library does.")
        inceptionYear.set("2023")
        url.set("https://github.com/username/mylibrary/")
        licenses {
            license {
                name.set("The Apache License, Version 2.0")
                url.set("http://www.apache.org/licenses/LICENSE-2.0.txt")
                distribution.set("http://www.apache.org/licenses/LICENSE-2.0.txt")
            }
        }
        developers {
            developer {
                id.set("username")
                name.set("User Name")
                url.set("https://github.com/username/")
            }
        }
        scm {
            url.set("https://github.com/username/mylibrary/")
            connection.set("scm:git:git://github.com/username/mylibrary.git")
            developerConnection.set("scm:git:ssh://git@github.com/username/mylibrary.git")
        }
    }
}

Secrets

For the publishing to work the credentials for Sonatype OSS as well as for the GPG key that is used for signing need to provided. To keep them out of version control it is recommended to either put this into the gradle.properties file user home or to use environment variables for publishing from CI servers.

mavenCentralUsername=username
mavenCentralPassword=the_password

signing.keyId=12345678
signing.password=some_password
signing.secretKeyRingFile=/Users/yourusername/.gnupg/secring.gpg

Please visit https://vanniktech.github.io/gradle-maven-publish-plugin/central/#configuring-maven-central for detailed instructions.

KtLint

This template applies the org.jlleitschuh.gradle.ktlint plugin to enforce the code style. To check the code style, run the following command:

./gradlew ktlintCheck

To automatically fix the code style, run the following command:

./gradlew ktlintFormat

This template also setup the git hooks to fix the code style before committing automatically. To install the git hooks, run the following command:

./gradlew setUpGitHooks

Then you can commit the code without worrying about the code style.

CI/CD

This template uses GitHub Actions to set up a CI/CD pipeline. Currently, the pipeline is configured to do three things:

Build the project

The pipeline is triggered on every push to the main branch or on every pull request. It builds the project and runs the tests.

The pipeline is defined in .github/workflows/build.yml.

Check the code style

The pipeline is triggered on every push to the main branch or on every pull request. It checks the code style and fails if the code style is not correct.

The pipeline is defined in .github/workflows/code_style.yml.

If the code style is not correct, you can run the following command to fix it:

./gradlew ktlintFormat

Publish the documentation

The pipeline is triggered on every push to the main branch or on every pull request. It generates the documentation and publishes it to GitHub Pages.

The pipeline is defined in .github/workflows/wiki.yml.

Dokka

This template applies the org.jetbrains.dokka plugin to generate documentation for the library code. To generate the documentation, run the following command:

./gradlew dokkaHtmlMultiModule

The documentation will be generated in the build/dokka/htmlMultiModule folder.

GitHub Pages

We also set up a GitHub Action to publish the documentation generated by Dokka to GitHub Pages. To make it work, you need to do the following:

1. Under your repository name, click Settings. If you cannot see the "Settings" tab, select the dropdown menu, then click Settings.
2. In the "Code and automation" section of the sidebar, click Pages.
3. Under "Build and deployment", under "Source", select Deploy from a branch.
4. Under "Build and deployment", use the branch dropdown menu and select the branch gh-pages as publishing sources. This branch will be created and updated automatically by configured GitHub actions when there are changes on the main branch.
5. Click Save.

You can also refer to https://docs.github.com/en/pages/getting-started-with-github-pages/configuring-a-publishing-source-for-your-github-pages-site for details.

Then the documentation will be published to https://<your-github-username>.github.io/<your-repository-name>/.

Set up the environment

Note Compose Multiplatform for iOS is in Alpha. It may change incompatibly and require manual migration in the future. We would appreciate your feedback on it in the public Slack channel #compose-ios. If you have any issues, please report them on GitHub.

You can use this template to start developing your own Compose Multiplatform mobile application targeting Android and iOS. Follow our tutorial below to get your first Compose Multiplatform app up and running. The result will be a Kotlin Multiplatform project that uses the Compose Multiplatform UI framework.

Warning You need a Mac with macOS to write and run iOS-specific code on simulated or real devices. This is an Apple requirement.

To work with this template, you need the following:

• A machine running a recent version of macOS
• Xcode
• Android Studio
• The Kotlin Multiplatform Mobile plugin
• The CocoaPods dependency manager

Check your environment

Before you start, use the KDoctor tool to ensure that your development environment is configured correctly:

1. Install KDoctor with Homebrew:

   brew install kdoctor
   

2. Run KDoctor in your terminal:

   kdoctor
   

   If everything is set up correctly, you'll see valid output:

   Environment diagnose (to see all details, use -v option):
   [✓] Operation System
   [✓] Java
   [✓] Android Studio
   [✓] Xcode
   [✓] Cocoapods
   
   Conclusion:
     ✓ Your system is ready for Kotlin Multiplatform Mobile development!
   

Otherwise, KDoctor will highlight which parts of your setup still need to be configured and will suggest a way to fix them.

Examine the project structure

Open the project in Android Studio and switch the view from Android to Project to see all the files and targets belonging to the project:

Your Compose Multiplatform project includes 3 modules:

shared

This is a Kotlin module that contains the logic common for both Android and iOS applications, that is, the code you share between platforms.

This shared module is also where you’ll write your Compose Multiplatform code. In shared/src/commonMain/kotlin/App.kt, you can find the shared root @Composable function for your app.

It uses Gradle as the build system. You can add dependencies and change settings in shared/build.gradle.kts. The shared module builds into an Android library and an iOS framework.

androidApp

This is a Kotlin module that builds into an Android application. It uses Gradle as the build system. The androidApp module depends on and uses the shared module as a regular Android library.

iosApp

This is an Xcode project that builds into an iOS application. It depends on and uses the shared module as a CocoaPods dependency.

Run your application

On Android

To run your application on an Android emulator:

1. Ensure you have an Android virtual device available. Otherwise, create one.

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

3. Choose your virtual device and click Run:

   

Alternatively, use Gradle

To install an Android application on a real Android device or an emulator, run ./gradlew installDebug in the terminal.

On iOS

Running on a simulator

To run your application on an iOS simulator in Android Studio, modify the iosApp run configuration:

1. In the list of run configurations, select Edit Configurations:

   

2. Navigate to iOS Application | iosApp.

3. In the Execution target list, select your target device. Click OK:

   

4. The iosApp run configuration is now available. Click Run next to your virtual device:

Running on a real device

You can run your Compose Multiplatform application on a real iOS device for free. To do so, you'll need the following:

• The TEAM_ID associated with your Apple ID
• The iOS device registered in Xcode

Note Before you continue, we suggest creating a simple "Hello, world!" project in Xcode to ensure you can successfully run apps on your device. You can follow the instructions below or watch this Stanford CS193P lecture recording.

How to create and run a simple project in Xcode

1. On the Xcode welcome screen, select Create a new project in Xcode.
2. On the iOS tab, choose the App template. Click Next.
3. Specify the product name and keep other settings default. Click Next.
4. Select where to store the project on your computer and click Create. You'll see an app that displays "Hello, world!" on the device screen.
5. At the top of your Xcode screen, click on the device name near the Run button.
6. Plug your device into the computer. You'll see this device in the list of run options.
7. Choose your device and click Run.

Finding your Team ID

In the terminal, run kdoctor --team-ids to find your Team ID. KDoctor will list all Team IDs currently configured on your system, for example:

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

Alternative way to find your Team ID

If KDoctor doesn't work for you, try this alternative method:

1. In Android Studio, run the iosApp configuration with the selected real device. The build should fail.
2. Go to Xcode and select Open a project or file.
3. Navigate to the iosApp/iosApp.xcworkspace file of your project.
4. In the left-hand menu, select iosApp.
5. Navigate to Signing & Capabilities.
6. In the Team list, select your team.

If you haven't set up your team yet, use the Add account option and follow the steps.

To run the application, set the TEAM_ID:

1. In the template, navigate to the iosApp/Configuration/Config.xcconfig file.
2. Set your TEAM_ID.
3. Re-open the project in Android Studio. It should show the registered iOS device in the iosApp run configuration.

Make your first changes

You can now make some changes in the code and check that they are visible in both the iOS and Android applications at the same time:

1. In Android Studio, navigate to the shared/src/commonMain/kotlin/App.kt file. This is the common entry point for your Compose Multiplatform app.

   Here, you see the code responsible for rendering the "Hello, World!" button and the animated Compose Multiplatform logo:

   @OptIn(ExperimentalResourceApi::class)
   @Composable
   fun App() {
       MaterialTheme {
           var greetingText by remember { mutableStateOf("Hello, World!") }
           var showImage by remember { mutableStateOf(false) }
           Column(Modifier.fillMaxWidth(), horizontalAlignment = Alignment.CenterHorizontally) {
               Button(onClick = {
                   greetingText = "Hello, ${getPlatformName()}"
                   showImage = !showImage
               }) {
                   Text(greetingText)
               }
               AnimatedVisibility(showImage) {
                   Image(
                       painterResource("compose-multiplatform.xml"),
                       null
                   )
               }
           }
       }
   }

2. Update the shared code by adding a text field that will update the name displayed on the button:

   @OptIn(ExperimentalResourceApi::class)
   @Composable
   fun App() {
       MaterialTheme {
           var greetingText by remember { mutableStateOf("Hello, World!") }
           var showImage by remember { mutableStateOf(false) }
           Column(Modifier.fillMaxWidth(), horizontalAlignment = Alignment.CenterHorizontally) {
               Button(onClick = {
                   greetingText = "Hello, ${getPlatformName()}"
                   showImage = !showImage
               }) {
                   Text(greetingText)
               }
   +           TextField(greetingText, onValueChange = { greetingText = it })
               AnimatedVisibility(showImage) {
                   Image(
                       painterResource("compose-multiplatform.xml"),
                       null
                   )
               }
           }
       }
   }

3. Re-run both the androidApp and iosApp configurations. You'll see this change reflected in both the Android and iOS apps:

   

How to configure the iOS application

To get a better understanding of this template's setup and learn how to configure the basic properties of your iOS app without Xcode, open the iosApp/Configuration/Config.xcconfig file in Android Studio. The configuration file contains:

• APP_NAME, a target executable and an application bundle name.
• BUNDLE_ID, which uniquely identifies the app throughout the system.
• TEAM_ID, a unique identifier generated by Apple that's assigned to your team.

To configure the APP_NAME option, open Config.xcconfig in any text editor before opening the project in Android Studio, and then set the desired name.

If you need to change this option after you open the project in Android Studio, do the following:

1. Close the project in Android Studio.
2. Run ./cleanup.sh in your terminal.
3. Change the setting.
4. Open the project in Android Studio again.

To configure advanced settings, use Xcode. After opening the project in Android Studio, open the iosApp/iosApp.xcworkspace file in Xcode and make changes there.

Next steps

We encourage you to explore Compose Multiplatform further and try out more projects:

• Learn about other cases for using the Compose Multiplatform UI framework
• Create an application targeting Windows, macOS, and Linux with Compose Multiplatform for Desktop
• Complete more Compose Multiplatform tutorials
• Explore some more advanced Compose Multiplatform example projects