Building for Every Platform with Kotlin Multiplatform

The dream of “write once, run anywhere” has been around for decades. With Kotlin Multiplatform (KMP), we are getting closer than ever, but with a pragmatic twist: “Share logic, keep native UI control” (though Compose Multiplatform is changing that too!).

In my project birds, I explored sharing not just the business logic but also the UI across Android and iOS using Compose Multiplatform.

The Shared Core

The core of the application resides in the shared module. This includes:

• Networking: Using Ktor for making API requests.
• Serialization: Using kotlinx.serialization for parsing JSON.
• State Management: ViewModels (or equivalent) that drive the UI state.

Compose Multiplatform

The real magic happens in the UI layer. With Compose Multiplatform, I could write the UI once in Kotlin and have it render natively on Android and via Skia on iOS.

@Composable
fun BirdList(birds: List<Bird>) {
    LazyColumn {
        items(birds) { bird ->
            BirdCard(bird)
        }
    }
}

The result is a fluid, high-performance application that feels at home on both platforms while sharing 90%+ of the codebase.