Distribute Kotlin Library

Release A Library Using The Plugin

We can distribute to other users a Kotlin library using native or third-party dependency, some requirements are necessary for Apple targets.

Requirement

The user must :

add the same native dependency used by the Kotlin library to his Xcode project.
use the same version as the library use.

It will fix issues with linking, missing resources, App Store compliance, and more.

Note

The user doesn't have access to the Kotlin library source code, which is great!

Publish Safe

Set publishSafe = true on a library you publish, so its klibs don't embed the paths of the build machine (every consumer would get ld: warning: search path '...' not found).

library/build.gradle.kts

swiftPackageConfig(cinteropName = "myBridge") {
    publishSafe = true
}

The library's own binaries still link. A consumer linking with Gradle rather than Xcode must provide the native dependencies through linkerOpts.

Example

A Compose Multiplatform Component library using a native video player.

commonMain/kotlin/KmpPlayer.kt

@Composable
public expect fun KmpPlayer(modifier: Modifier = Modifier, url: String)

Android

For Android, it uses Exoplayer.

Gradle

library/build.gradle.kts

androidMain.dependencies {
    implementation(libs.media3.exoplayer)
    implementation(libs.media3.exoplayer.dash)
    implementation(libs.media3.ui)
}

AndroidMain

androidMain/kotlin/KmpPlayer.kt

@Composable
public actual fun KmpPlayer(modifier: Modifier, url: String) {

    val context = LocalContext.current

    // Initialize ExoPlayer
    val exoPlayer = ExoPlayer.Builder(context).build()

    val mediaSource = remember(url) {
        MediaItem.fromUri(url)
    }


    LaunchedEffect(url) {
        exoPlayer.setMediaItem(mediaSource)
        exoPlayer.prepare()
    }

    // Manage lifecycle events
    DisposableEffect(Unit) {
        onDispose {
            exoPlayer.release()
        }
    }

    AndroidView(
        factory = { ctx ->
            PlayerView(ctx).apply {
                player = exoPlayer
            }
        },
        modifier = modifier
    )
}

iOS

For iOS, it uses KSPlayer, it's a pure Swift library.

Gradle

library/build.gradle.kts

kotlin {
    iosArm64 {
        swiftPackageConfig(cinteropName = "appleDeps") {
            minIos = "13.0"
            minMacos = "10.15"
            minTvos = "13.0"
            minWatchos = "2.0"
            dependency {
                remotePackageBranch(
                    url = URI("https://github.com/kingslay/KSPlayer"),
                    products = {
                        add("KSPlayer")
                    },
                    branch = "main"
                )
            }
        }
    }
}

Bridge

Some tips here.

src/swift/appleDeps/MEPlayerController.swift

import Foundation
import KSPlayer

@objcMembers public class MEPlayerController: NSObject {
     private let player = IOSVideoPlayerView()

    override init() {
       super.init()
       KSOptions.secondPlayerType = KSMEPlayer.self
       player.delegate = self
       player.autoresizingMask = [.flexibleWidth, .flexibleHeight]
       player.contentMode = .scaleAspectFill
    }

    public func setMediaItem(videoUrl: URL) {
       player.set(
          url: videoUrl,
          options: KSOptions()
      )
    }

    public var playerView: NSObject {
       player
    }

    public func releasePlayer() {
       player.resetPlayer()
       player.removeFromSuperview()
    }
}

IOSMain

iosMain/kotlin/KmpPlayer.kt

import appleDeps.MEPlayerController

@Composable
public actual fun KmpPlayer(modifier: Modifier, url: String) {

    val playerController = MEPlayerController()

    val mediaSource = remember(url) {
        NSURL.URLWithString(url)
    }

    LaunchedEffect(url) {
        if (mediaSource == null) {
            throw Exception("Bad input URL")
        }
        playerController.setMediaItemWithVideoUrl(videoUrl = mediaSource)
    }

    DisposableEffect(Unit) {
        onDispose {
            playerController.releasePlayer()
        }
    }

    UIKitView(
        factory = {
            playerController.playerView() as UIView
        },
        modifier = modifier,
        update = {
        }
    )
}

Requirement

The setup guide of your library must contain the rule that KSPlayer package must be added to his Xcode project with the explicit version.

Sample

The sample is available.

Run the command ./gradlew publishToMavenLocal --no-configuration-cache on the repository root.
Open the project sampleApp and test the application