Integrating Koin with Jetpack Compose

In our previous blog, we introduced Koin and set up a simple "Hello Koin" example to demonstrate dependency injection. Now, let’s take it a step further and explore how to integrate Koin with Jetpack Compose. This guide will help you leverage Koin to manage dependencies seamlessly in a modern Compose-based Android application.

Why Use Koin with Jetpack Compose?

Jetpack Compose is Android’s modern UI toolkit, and Koin’s Kotlin-first approach makes it an ideal match. Together, they provide:

Simplified dependency management: Koin handles dependencies, freeing you from manual instantiation.
Cleaner code: Compose’s declarative UI and Koin’s DSL complement each other for concise, readable code.
Scalability: Easy to manage dependencies across a growing application.

Setting Up Koin for Jetpack Compose

Step 1: Add Dependencies

Add the following dependencies to your build.gradle file:

implementation "io.insert-koin:koin-android:3.x.x"
implementation "io.insert-koin:koin-androidx-compose:3.x.x"

Replace 3.x.x with the latest version of Koin.

Step 2: Define Your Koin Modules

Let’s create a module for our Compose-based app. Assume we have a GreetingService to provide messages:

class GreetingService {
    fun getGreeting() = "Hello from Koin!"
}

val appModule = module {
    single { GreetingService() }
}

Step 3: Initialize Koin

Initialize Koin in your Application class:

import android.app.Application
import org.koin.core.context.startKoin

class MyApplication : Application() {
    override fun onCreate() {
        super.onCreate()

        startKoin {
            modules(appModule)
        }
    }
}

Declare the Application class in your AndroidManifest.xml file:

<application
    android:name=".MyApplication"
    ...>
</application>

Step 4: Inject Dependencies in Compose

Koin provides seamless integration with Compose using the koinComponent() and get() functions.

Here’s an example:

Create a Composable Function

import androidx.compose.runtime.Composable
import androidx.compose.material3.Text
import org.koin.androidx.compose.koinInject

@Composable
fun GreetingScreen() {
    val greetingService: GreetingService = koinInject()
    Text(text = greetingService.getGreeting())
}

In this example:

koinInject() retrieves the GreetingService instance from Koin.
The GreetingService is then used to display a greeting message.

Step 5: Set Up Your Compose UI

In your MainActivity, set the Compose content:

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.material3.MaterialTheme

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MaterialTheme {
                GreetingScreen()
            }
        }
    }
}

Running the App

When you run the app, the GreetingScreen will display the text: Hello from Koin!.

Exploring Advanced Features

Koin offers additional features for Compose integration, such as:

Using ViewModel with Compose

Koin’s viewModel() delegate simplifies ViewModel injection in Compose. Here’s an example:

Define a ViewModel

import androidx.lifecycle.ViewModel

class GreetingViewModel(private val greetingService: GreetingService) : ViewModel() {
    fun getGreetingMessage() = greetingService.getGreeting()
}

val viewModelModule = module {
    viewModel { GreetingViewModel(get()) }
}

Use the ViewModel in Compose

import androidx.compose.runtime.Composable
import org.koin.androidx.compose.koinViewModel

@Composable
fun GreetingScreen(viewModel: GreetingViewModel = koinViewModel()) {
    Text(text = viewModel.getGreetingMessage())
}

Passing Parameters

Koin supports parameter injection for more dynamic behavior. For instance:

val appModule = module {
    factory { (name: String) -> GreetingService(name) }
}

@Composable
fun GreetingScreen() {
    val greetingService: GreetingService = get { parametersOf("Compose") }
    Text(text = greetingService.getGreeting())
}

Akshay Nandwana
Founder AndroidEngineers

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