Kotlin Multiplatform at Stable and Beyond (Kotlin Vienna, October 2024)

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Kotlin Multiplatform at Stable and Beyond Márton Braun Developer Advocate

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iOS Android Desktop Web Server

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iOS Android Desktop Web Server

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iOS Android Desktop +

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.kt .kt .kt .kt Android Desktop iOS Common

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.kt .kt .kt .kt Android Desktop iOS Common

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.kt .kt .kt Android Desktop iOS Common class Person(val name: String, var age: Int) fun greet(person: Person) { println("Hello, ${person.name}") }

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.kt .kt .kt Android Desktop iOS Common fun List.duplicates(): Map { return map { it.name.substringBefore(" ") } .groupingBy { it } .eachCount() .filter { (name, count) -> count > 1 } }

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Android Desktop iOS actual Common expect actual actual

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Android Desktop iOS Common expect actual actual actual

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Android Desktop iOS Common fun getPlatform(): String expect actual actual actual

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Android Desktop iOS Common fun getPlatform(): String fun getPlatform(): String = "Java ${System.getProperty("java.version")}" expect actual actual actual

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Android iOS fun getPlatform(): String = "Android ${Build.VERSION.SDK_INT}" actual actual Common fun getPlatform(): String expect Desktop fun getPlatform(): String = "Java ${System.getProperty("java.version")}" actual

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Android iOS fun getPlatform(): String = "iOS ${UIDevice.currentDevice.systemVersion}" fun getPlatform(): String = "Android ${Build.VERSION.SDK_INT}" actual actual Common fun getPlatform(): String expect Desktop fun getPlatform(): String = "Java ${System.getProperty("java.version")}" actual

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Android Desktop iOS Common fun getPlatform(): String fun getPlatform(): String = "Java ${System.getProperty("java.version")}" fun getPlatform(): String = "iOS ${UIDevice.currentDevice.systemVersion}" fun getPlatform(): String = "Android ${Build.VERSION.SDK_INT}" expect actual actual actual

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Multiplatform libraries

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github.com/terrakok/kmp-awesome

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.kt .kt .kt Android Desktop iOS Common import io.ktor.client.* suspend fun loadHtml(): String { val client = HttpClient() val response = client.get("https://kotlinlang.org") return response.body() }

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Shared logic

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Shared logic Swing Desktop logic Jetpack Compose Android logic SwiftUI iOS logic

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Shared logic Swing Desktop logic Jetpack Compose Android logic SwiftUI iOS logic

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Shared logic Swing Desktop logic Jetpack Compose Android logic SwiftUI iOS logic

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2019 2020 2021 2022 2023 2024 2025 Experimental ➟

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Alpha 2019 2020 2021 2022 2023 2024 2025

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Beta 2019 2020 2021 2022 2023 2024 2025

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Stable 2019 2020 2021 2022 2023 2024 2025

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Stable 2019 2020 2021 2022 2023 2024 2025

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Compiler support Language features Library APIs Build tooling IDE support Strict compatibility guarantees kotl.in/kmp-stability

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Configuring targets kotlin { androidTarget() iosArm64() iosSimulatorArm64() sourceSets { val commonMain by getting val iosMain by creating { dependsOn(commonMain) } val iosArm64Main by creating { dependsOn(iosMain) } val iosSimulatorArm64Main by creating { dependsOn(iosMain) } } }

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Configuring targets kotlin { androidTarget() iosArm64() iosSimulatorArm64() }

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common jvm android native js androidNative apple mingw linux iosArm64 iosSimulatorArm64 mingwX64 android_arm64 ... ios macos tvos watchos Configuring targets kotlin { androidTarget() iosArm64() iosSimulatorArm64() } iosArm64 iosX64 iosSimulatorArm64 iosArm64 iosSimulatorArm64 iosArm64 iosSimulatorArm64 iosArm64 iosSimulatorArm64

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common jvm android native js androidNative apple mingw linux iosArm64 iosSimulatorArm64 mingwX64 android_arm64 ... ios macos tvos watchos Configuring targets kotlin { androidTarget() iosArm64() iosSimulatorArm64() } iosX64 iosArm64 iosSimulatorArm64 iosArm64 iosSimulatorArm64 iosArm64 iosSimulatorArm64 iosArm64 iosSimulatorArm64

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common jvm android native js androidNative apple mingw linux iosArm64 iosSimulatorArm64 mingwX64 android_arm64 ... ios macos tvos watchos Configuring targets kotlin { androidTarget() iosArm64() iosSimulatorArm64() iosX64 iosArm64 iosSimulatorArm64 iosArm64 iosSimulatorArm64 iosArm64 iosSimulatorArm64 iosArm64 iosSimulatorArm64 }

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Configuring targets kotlin { androidTarget() iosArm64() iosSimulatorArm64() sourceSets { } } m m o c

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Configuring targets kotlin { androidTarget() iosArm64() iosSimulatorArm64() sourceSets { commonMain } }

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Configuring targets kotlin { androidTarget() iosArm64() iosSimulatorArm64() sourceSets { commonMain.dependencies { implementation(libs.ktor.client.core) } androidMain.dependencies { implementation(libs.ktor.client.okhttp) } iosMain.dependencies { implementation(libs.ktor.client.darwin) } } }

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Gradle configuration cache support Build and runtime performance 📈 Incremental compilation of klib artifacts 🧪 New custom memory allocator in Kotlin/Native Kotlin/Native compiler cache management

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kotl.in/kmp-portal

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Kotlin-Swift interopedia kotl.in/interopedia forked from hhru/kotlin-swift-interopedia

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Currently via Objective-C

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Work in progress via Objective-C

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Work in progress github.com/Kotlin/swift-export-sample

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Demo kmp.jetbrains.com

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Public Preview

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Demo

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Shared logic Swing Desktop logic Jetpack Compose Android logic SwiftUI iOS logic

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Shared logic Swing Desktop logic Jetpack Compose Android logic SwiftUI iOS logic

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jb.gg/compose Compose Multiplatform

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Compose Multiplatform jb.gg/compose

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@Composable fun SquaresGalleryView( images: List, selectedImage: PictureData, onSelect: (PictureData) -> Unit, ) { LazyVerticalGrid( modifier = Modifier.padding(top = 4.dp), columns = GridCells.Adaptive(minSize = 130.dp), verticalArrangement = Arrangement.spacedBy(1.dp), horizontalArrangement = Arrangement.spacedBy(1.dp) ) { itemsIndexed(images) { _, picture -> SquareThumbnail( picture = picture, onClick = { onSelect(picture) }, isHighlighted = selectedImage === picture ) } } }

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Swing Desktop logic Jetpack Compose Android logic SwiftUI iOS logic Shared logic

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Desktop logic Android logic iOS logic Shared logic Shared UI Compose Multiplatform

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Desktop logic Android logic iOS logic Shared logic Shared UI Compose Multiplatform Swing Jetpack Compose SwiftUI

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Latest developments Resources 1.6.0+ Lifecycle Navigation 2.8.0 2.8.0-alpha09 ViewModel 2.8.0

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Resources org.jetbrains.compose.components:components-resources composeResources

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Resources org.jetbrains.compose.components:components-resources drawable files font values composeResources

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Resources org.jetbrains.compose.components:components-resources drawable files font values -de -en-rUS -mdpi -xxhdpi -light -dark composeResources

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Demo

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Resources • Multi-module projects and library publication • Configuration options for generated file • Plural strings • Resource directories in multiple source sets

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Lifecycle org.jetbrains.androidx.lifecycle:lifecycle-common

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Lifecycle on Desktop org.jetbrains.androidx.lifecycle:lifecycle-runtime-compose Swing listener callbacks Lifecycle event Lifecycle state change windowLostFocus ON_PAUSE RESUMED → STARTED windowGainedFocus ON_RESUME STARTED → RESUMED windowIconified ON_STOP STARTED → CREATED windowDeiconified ON_START CREATED → STARTED dispose ON_DESTROY CREATED → DESTROYED

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Demo

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ViewModel org.jetbrains.androidx.lifecycle:lifecycle-viewmodel-compose package androidx.lifecycle public abstract class ViewModel { protected open fun onCleared() public fun addCloseable(key: String, closeable: AutoCloseable) public open fun addCloseable(closeable: AutoCloseable) } public val ViewModel.viewModelScope: CoroutineScope

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ViewModelStoreOwner implementations Who owns the ViewModel?

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ViewModelStoreOwner implementations 🗄 ComponentActivity ComposeView ComponentActivity Who owns the ViewModel?

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ViewModelStoreOwner implementations 🗄 ComponentActivity ComposeView ComponentActivity Who owns the ViewModel?

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ViewModelStoreOwner implementations SwiftUI 🗄 ComposeUIVC ComponentActivity ComposeUIViewController ComposeWindow CanvasBasedWindow Who owns the ViewModel?

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ViewModelStoreOwner implementations SwiftUI 🗄 ComposeUIVC ComponentActivity ComposeUIViewController ComposeWindow CanvasBasedWindow Who owns the ViewModel?

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ViewModelStoreOwner implementations NavBackStackEntry🗄 NavBackStackEntry🗄 NavBackStackEntry ComponentActivity ComposeUIViewController ComposeWindow CanvasBasedWindow Who owns the ViewModel? 🗄 ComposeUIVC

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ViewModelStoreOwner implementations YourCustomOwner 🗄 Provide your own! NavBackStackEntry ComponentActivity ComposeUIViewController ComposeWindow CanvasBasedWindow Who owns the ViewModel?

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Navigation org.jetbrains.androidx.navigation:navigation-compose val controller = rememberNavController() NavHost(navController = controller, startDestination = "list") { composable("list") { ListScreen( navToDetails = { objectId -> controller.navigate("details/$objectId" } ) } composable("details/{objectId}") { backStack -> DetailScreen( objectId = backStack.arguments?.getString("objectId"), navBack = { controller.popBackStack() } ) } } )

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Navigation org.jetbrains.androidx.navigation:navigation-compose val controller = rememberNavController() NavHost(navController = controller, startDestination = ListDestination) { composable { ListScreen( navToDetails = { objectId -> controller.navigate(DetailDestination(objectId) } ) } composable { backStack -> DetailScreen( objectId = backStack.toRoute().objectId, navBack = { controller.popBackStack() } ) } } )

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Demo

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Amper Experimental jb.gg/amper

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Demo

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jb.gg/amper jb.gg/amper-slack jb.gg/amper-issues jb.gg/amper-blog

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Kotlin Multiplatform jb.gg/kmp Compose Multiplatform jb.gg/compose jb.gg/compose-resources jb.gg/compose-navigation jb.gg/compose-lifecycle Fleet jb.gg/fleet Amper jb.gg/amper Kotlin Multiplatform at Stable and Beyond zsmb.co/talks Márton Braun @zsmb13@androiddev.social