Introducing Kotlin Multiplatform in an existing mobile app - Workshop Edition | DevFest Kosova

After discovering a new interesting technology or framework, you will probably start asking yourself how to integrate it into an existing project. That's because, the possibility of starting with a blank canvas is rare (not impossible, but rare).

This is also the case for Kotlin Multiplatform, which is getting more and more hype every day. And now, that the technology has become stable, it's the perfect time to start using it! In this hands-on session, we will start with an existing Android and iOS application that "lives" in separate repositories, we will extract the business logic from the Android app and share it between the two apps with a Kotlin Multiplatform library. We will also cover how to distribute the library to the existing applications. By the end of this workshop, you'll have a better understanding of what is needed to start using Kotlin Multiplatform in your existing projects.

Transcript

1. @marcogomiero.com Marco Gomiero Senior Android Engineer @ Airalo Google Developer Expert for Kotlin Introducing Kotlin Multiplatform in an existing mobile app workshop edition
2. @marcogomiero.com Prerequisites • Download Android Studio and the Kotlin Multiplatform Plugin • Download Xcode You can check if your system is ready for Kotlin Multiplatform with kdoctor: https: // github.com/Kotlin/kdoctor
3. @marcogomiero.com bit.ly/kmp-existing-app-workshop
4. @marcogomiero.com Agenda • Quick intro about Kotlin Multiplatform • Start from an Android and iOS native app - that lives in separate repositories and extract the business logic from Android into a new KMP library • Deploy the library on Android • Break ☕ • Deploy the library on iOS • iOS API enhancements • How to deploy in a scalable way
5. @marcogomiero.com What is Kotlin Multiplatform?
6. @marcogomiero.com “Classic” Cross Platform Solutions • All-in approach • Everything is shared, UI included • Different platforms have different patterns
7. @marcogomiero.com Kotlin Multiplatform • Incremental approach • You choose what to share (even UI, if you want)
8. @marcogomiero.com Photo by Erwan Hesry on Unsplash 💡 Create a library!
9. @marcogomiero.com Common Kotlin Kotlin/JVM Kotlin/JS Kotlin/Native JVM Android Browser NodeJS iOS macOS watchOS tvOS Linux Windows Supported Platforms Kotlin/Wasm Browser Alpha
10. @marcogomiero.com Common Kotlin Kotlin/JVM Kotlin/JS Kotlin/Native JVM Android Browser NodeJS iOS macOS watchOS tvOS Linux Windows Mobile Kotlin/Wasm Browser Alpha
11. @marcogomiero.com How it works?
12. @marcogomiero.com shared androidApp iosApp Library Library iOS Android
13. @marcogomiero.com shared androidApp Gradle Module Android Same repository
14. @marcogomiero.com shared androidApp .aar Android Different repositories
15. @marcogomiero.com iosApp iOS shared XCFramework Different repositories Same repository
16. @marcogomiero.com XCFramework https://developer.apple.com/documentation/xcode/creating-a-multi-platform-binary-framework-bundle
17. @marcogomiero.com NEW https://devstreaming-cdn.apple.com/videos/wwdc/2019/416h8485aty341c2/416/416_binary_frameworks_in_swift.pdf
18. @marcogomiero.com https://devstreaming-cdn.apple.com/videos/wwdc/2019/416h8485aty341c2/416/416_binary_frameworks_in_swift.pdf NEW iOS mac OS watch OS tvOS
19. @marcogomiero.com shared androidApp iosApp Gradle Module XCFramework Same Repository Easier for new projects
20. @marcogomiero.com Common Kotlin Android App iOS App .aar XCFramework Android App Repository KMP Repository iOS App Repository Easier for existing projects
21. @marcogomiero.com Code Time 🧑💻
22. @marcogomiero.com XCFramework https://developer.apple.com/documentation/xcode/creating-a-multi-platform-binary-framework-bundle
23. @marcogomiero.com iOS Dependency Managers • CocoaPods • Carthage • Swift Package Manager 💀 💀 ✅
24. @marcogomiero.com Swift Package Manager • Based on git • Configured with a Package.swift file • Semantic versioning (e.g. 1.2.3) with git tags • Can contain code or binaries • Can be local or remote, it’s git!
25. @marcogomiero.com Code Time 🧑💻
26. @marcogomiero.com shared iosApp Framework iOS Kotlin Objective-C Swift -> ->
27. @marcogomiero.com Some gotchas • No namespaces • No default parameters • Enums are not Swift-friendly (no values) • Sealed classes are simple classes • Coroutines without cancellation • Flows
28. @marcogomiero.com https://kotlinlang.org/docs/whatsnew21.html#basic-support-for-swift-export
29. @marcogomiero.com Code Time 🧑💻
30. @marcogomiero.com Swift Package Manager https://twitter.com/kpgalligan/status/1723364386046173493
31. @marcogomiero.com Code Time 🧑💻
32. @marcogomiero.com Conclusions • You choose what to share (even UI, if you want) • Validate the process with “little” effort • Find the best (for you) approach/infrastructure • Then you can go bigger and share more “features”
33. @marcogomiero.com Thank you! Marco Gomiero Senior Android Engineer @ Airalo Google Developer Expert for Kotlin > Twitter: @marcoGomier > Github: prof18 > Website: marcogomiero.com > Mastodon: androiddev.social/@marcogom > BlueSky: @marcogomiero.com
34. Bibliography / Useful Links • https: // docs.github.com/en/actions/publishing-packages/publishing-java-packages-with-gradle • https: // github.com/orgs/community/discussions/26328#discussioncomment-3251485 • https: // github.com/orgs/community/discussions/26634 • https: // developer.apple.com/documentation/xcode/creating-a-multi-platform-binary-framework-bundle • https: // devstreaming-cdn.apple.com/videos/wwdc/2019/416h8485aty341c2/416/416_binary_frameworks_in_swift.pdf • https: // kotlinlang.org/docs/multiplatform-build-native-binaries.html • https: // developer.apple.com/documentation/xcode/distributing-binary-frameworks-as-swift-packages • https: // github.com/rickclephas/KMP-NativeCoroutines • https: // skie.touchlab.co/ • https: // touchlab.co/skie-migration?ti=4B0F129C5D944E54B60B31FE35 • https: // kotlinlang.org/docs/native-objc-interop.html • https: // kotlinlang.org/docs/apple-framework.html • https: // github.com/kotlin-hands-on/kotlin-swift-interopedia • https: // medium.com/@aoriani/list/writing-swiftfriendly-kotlin-multiplatform-apis-c51c2b317fce • https: // blog.devgenius.io/dependancy-management-for-ios-27dd681d7ea0 • https: // github.com/luca992/multiplatform-swiftpackage • https: // touchlab.co/kmmbridge/ • https: // touchlab.co/kmmbridge/spmquickstart • https: // medium.com/geekculture/xcode-13-3-supports-spm-binary-dependency-in-private-github-release-8d60a47d5e45 • https: // touchlab.co/xcodekotlin • https: // kotlinlang.org/docs/native-spm.html#swift-package-distribution • https: // github.com/JetBrains/kotlin/tree/master/docs/swift-export • https: // github.com/Kotlin/swift-export-sample