Kotlin Multiplatform Android — Complete Guide

// Putting Android Context in commonMain
// commonMain
class MyRepository(context: Context) { // Context doesn't exist in commonMain!
    // ...
}

// build.gradle.kts — shared module
kotlin {
    androidTarget()

    sourceSets {
        val androidMain by getting {
            dependencies {
                implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:2.7.0")
                implementation("androidx.room:room-runtime:2.6.1")
                implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.8.0")
            }
        }
        val commonMain by getting {
            dependencies {
                implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.8.0")
                implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.6.3")
            }
        }
    }
}

// commonMain
expect class PlatformContext

expect class DatabaseFactory {
    fun createDatabase(): Database
}

// androidMain
actual typealias PlatformContext = android.content.Context

actual class DatabaseFactory(private val context: PlatformContext) {
    actual fun createDatabase(): Database {
        val db = Room.databaseBuilder(
            context,
            AppDatabase::class.java, "shared-db"
        ).build()
        return AndroidDatabase(db)
    }
}

// Using in Android app
class MainActivity : AppCompatActivity() {
    private val factory = DatabaseFactory(this)
    private val db = factory.createDatabase()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // db is ready
    }
}