Compose Multiplatform App Distribution: A Comprehensive Guide

Kotlin Multiplatform (KMP) and Jetpack Compose offer a compelling solution for building cross-platform applications with a single codebase. While development is exciting, distributing a Compose Multiplatform app requires a thoughtful approach to cater to each platform’s specific requirements. This post dives into the different methods for distributing your Compose Multiplatform apps.

Understanding Compose Multiplatform App Distribution

Distributing a Compose Multiplatform app means packaging your code in a way that’s executable on various target platforms, such as Android, iOS, desktop (Windows, macOS, Linux), and web. Each platform has its own distribution mechanisms and requirements, making the process more intricate than single-platform development.

Key Distribution Considerations

• Platform-Specific Packaging: Different platforms necessitate distinct packaging formats (e.g., APK/AAB for Android, IPA for iOS, DMG/EXE for desktop, and HTML/JavaScript for web).
• Code Signing and Certificates: Securing and verifying your application’s authenticity via code signing is essential, particularly on platforms like iOS and macOS.
• Store Submission Guidelines: Each app store (Google Play Store, Apple App Store) possesses unique submission guidelines and policies.
• Dependency Management: Managing platform-specific dependencies is crucial to avoid conflicts and ensure proper app functioning.
• Automated Build and Release Pipelines: Streamlining the distribution process by using CI/CD tools helps automate testing, building, and publishing to app stores.

Distribution Methods for Each Platform

1. Android Distribution

For Android, distribution involves creating either an APK (Android Package Kit) or AAB (Android App Bundle). AAB is the preferred format for Google Play Store as it allows Google Play to optimize the app delivery based on the user’s device configuration.

Steps for Android Distribution

1. Configure Build Variants: Set up different build variants (e.g., debug, release) in your build.gradle.kts file.
2. Signing Configuration: Define signing configurations to sign your release build.
3. Generate APK/AAB: Use Gradle tasks to generate the APK or AAB file.
4. Submit to Google Play Store: Follow Google Play Store guidelines to submit your app.

android {
    ...
    signingConfigs {
        release {
            storeFile = file("path/to/your/keystore.jks")
            storePassword = "your_store_password"
            keyAlias = "your_key_alias"
            keyPassword = "your_key_password"
        }
    }
    buildTypes {
        release {
            signingConfig = signingConfigs.release
            minifyEnabled true // Enable ProGuard/R8
            shrinkResources true
        }
    }
    bundle {
        storeArchiveName.set("your_app_name.aab")
    }
}

Generate AAB using Gradle:

./gradlew bundleRelease

2. iOS Distribution

Distributing your app on iOS involves packaging it as an IPA (iOS App Archive). This process requires obtaining the necessary certificates and provisioning profiles from Apple Developer Program.

Steps for iOS Distribution

1. Enroll in Apple Developer Program: Obtain an Apple Developer Account.
2. Create Certificates and Profiles: Generate necessary certificates (Development and Distribution) and provisioning profiles on Apple Developer Portal.
3. Configure Xcode Project: Open the iOS project in Xcode, configure signing settings, and select the appropriate team and provisioning profile.
4. Archive the App: Use Xcode to create an archive of your application.
5. Distribute the App: Distribute via TestFlight for beta testing or directly to the App Store.

Due to the nature of iOS distribution involving Xcode and the Apple ecosystem, a comprehensive code example is beyond the scope of raw HTML. However, ensure your build.gradle.kts generates the necessary .klib files for Xcode to use.

3. Desktop (Windows, macOS, Linux) Distribution

Desktop distribution involves creating platform-specific executables or package formats such as DMG (macOS), EXE (Windows), and DEB/RPM (Linux).

Steps for Desktop Distribution

1. Configure Gradle: Set up Gradle tasks to build native executables for each platform.
2. Use Native Packagers: Utilize tools like jpackage (for creating platform-specific installers).
3. Code Signing: For macOS and Windows, sign the executables to ensure user trust.

Here’s an example configuration in build.gradle.kts for desktop distribution:

kotlin {
    ...
    jvm("desktop") {
        compilations.all {
            kotlinOptions.jvmTarget = "11"
        }
        withJava()
        
        val mainClass = "MainKt"
        
        // Native distribution using jpackage
        tasks.register("packageDesktop", org.jetbrains.kotlin.gradle.tasks.KotlinNativeLink::class) {
            val os = org.apache.commons.lang.SystemUtils.OS_NAME
            val targetName = "YourAppName"
            val outputDir = buildDir.resolve("package")

            
            destinationDir.set(outputDir)
            group = "distribution"
            dependsOn(assemble)

            // Define launcher
            mainClassName = mainClass

            doLast {
                // Determine which operating system this is being built from
                // Build a list of params
                val jpackageParams = mutableListOf(
                    "jpackage",
                    "--type",
                    when {
                        os.startsWith("Windows") -> "exe"
                        os.startsWith("Mac") -> "dmg"
                        else -> "deb" // Linux is often done as deb, but other types exist too
                    },
                    "--name",
                    targetName,
                    "--dest",
                    outputDir.absolutePath,
                    "--input",
                    jar.archiveFile.get().asFile.absolutePath,
                    "--main-class",
                    mainClass
                )

                // If on MacOS add mac-specific parameters
                if (os.startsWith("Mac")) {
                    jpackageParams.add("--mac-package-identifier")
                    jpackageParams.add("com.YourCompany.$targetName")
                }

                // Finally, actually run the command
                ProcessBuilder(jpackageParams).start().waitFor()
            }
        }
    }
}

4. Web Distribution

For web distribution, you’ll compile your Kotlin code to JavaScript. This involves using Kotlin/JS and deploying the resulting artifacts (HTML, JavaScript, CSS) to a web server.

Steps for Web Distribution

1. Configure Kotlin/JS: Set up the Kotlin/JS plugin in your Gradle file.
2. Compile to JavaScript: Use Gradle tasks to compile your Kotlin code to JavaScript.
3. Deploy to Web Server: Copy the generated HTML, JavaScript, and CSS files to a web server (e.g., Apache, Nginx).

Here’s an example configuration in build.gradle.kts for web distribution:

kotlin {
    js(IR) {
        browser {
            distribution {
                outputDir = project.file("web/js")
                // For single page application, enable the following line:
                // + automatically generates `index.html` file
                singlePageApplication = true
            }
            testTask {
                useKarma {
                    useChromeHeadless()
                }
            }
        }
        binaries.executable()
    }
}

After building the project, you can find the compiled JavaScript and HTML files in the specified output directory (web/js in this example).

Best Practices for Compose Multiplatform App Distribution

• Automate Your Builds: Use CI/CD tools like Jenkins, GitHub Actions, or GitLab CI to automate the build, test, and release processes.
• Version Control: Maintain strict version control to manage changes and facilitate rollbacks.
• Comprehensive Testing: Implement thorough testing (unit, integration, UI) to ensure stability across all platforms.
• Dependency Management: Leverage dependency management tools like Gradle or Maven to handle cross-platform dependencies effectively.
• Code Signing: Always sign your applications to provide users with secure and verifiable software.

Conclusion

Distributing Compose Multiplatform apps demands a clear understanding of each platform’s requirements and the adoption of robust distribution strategies. By meticulously configuring platform-specific builds, leveraging automation, and adhering to best practices, you can efficiently deliver your Compose Multiplatform apps to users on Android, iOS, desktop, and the web. This ensures a smooth, secure, and consistent user experience across diverse environments.