Kotlin Library Project

Source Code

Swift Stream automatically generates the initial Kotlin Library project for you. Its gradle files keeps in sync with your Swift code, however the rest is assumed to be maintained by you.

During experiments you can always just remove Library folder and rebuild Swift project to regenerate it

Here’s a sample of the generated Kotlin interface:

import android.util.Log

object SwiftInterface {
    init {
        System.loadLibrary("MyFirstAndroidProject")
    }

    external fun initialize(caller: Any)

    external fun sendInt(number: Int)
    external fun sendIntArray(array: IntArray)
    external fun sendString(string: String)
    external fun sendDate(date: Date)
    external fun ping(): String
    external fun fetchAsyncData(): String
}

Gradle Files

Swift Stream IDE automatically manages your Gradle project files. It generates Java packages based on your Swift targets from Package.swift and keeps all the Gradle files in sync.

In Library/settings.gradle.kts, it manages the list of included targets within special comment tags:

// managed by swiftstreamide: includes-begin
include(":myfirstandroidproject")
// managed by swiftstreamide: includes-end

It reflects the list of library products declared in your Package.swift.

In each Library/<target>/build.gradle.kts file, it manages dependencies based on the imports in your Swift code and the Swift version you're using:

// managed by swiftstreamide: so-dependencies-begin
implementation("com.github.swifdroid.runtime-libs:core:6.2.0")
implementation("com.github.swifdroid.runtime-libs:foundation:6.2.0")
implementation("com.github.swifdroid.runtime-libs:foundationessentials:6.2.0")
implementation("com.github.swifdroid.runtime-libs:i18n:6.2.0")
// managed by swiftstreamide: so-dependencies-end

It works this way because soMode setting is set to Packed by default. Read

If you need more control, you can take over manually, still without the hassle of manual file copying.

Read more about → so-mode and how to customize it.

Assemble with Gradle

To build the distributable Android library files (.aar), just hit Java Library Project -> Assemble in the Swift Stream sidebar.

This command runs either gradlew assembleDebug or gradlew assembleRelease in the background, packaging everything up for distribution.

Getting the .AAR File

Now, grab your freshly built library file! You'll find the .aar file in your Swift Stream project at this path:

📦 Project Root
├── 📄 Package.swift
└── 📂 Library
    └── 📂 myfirstandroidproject
        └── 📂 build
            └── 📂 outputs
                └── 📂 aar
                    └── 📄 myfirstandroidproject-debug.aar

Copy this file. Then, in your Android Studio project, navigate to your app module's directory (e.g., app/) and create a folder named libs right next to the build.gradle.kts file. Paste the .aar file into this new libs folder.