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Koin for Jetpack Compose and Compose Multiplatform

This page describe how you can inject your dependencies for your Android Jetpack Compose or your Multiplaform Compose apps.

Koin Compose Multiplatform vs Koin Android Jetpack Compose​

Since mid 2024, Compose applications can be done with Koin Multiplatform API. All APIs are identifcal between Koin Jetpack Compose (koin-androidx-compose) and Koin Compose Multiplatform (koin-compose).

What Koin package for Compose?​

for a pure Android app that uses only Android Jetpack Compose API, use the following packages:

  • koin-androidx-compose - to unlock Compose base API + Compose ViewModel API
  • koin-androidx-compose-navigation - Compose ViewModel API with Navigation API integration

for an Android/Multiplatform app, use the following packages:

  • koin-compose - Compose base API
  • koin-compose-viewmodel - Compose ViewModel API
  • koin-compose-viewmodel-navigation - Compose ViewModel API with Navigation API integration

Starting Koin in a Compose App with KoinApplication​

The function KoinApplication helps to create Koin application instance, as a Composable:

@Composable
fun App() {
    KoinApplication(application = {
        modules(...)
    }) {
        
        // your screens here ...
        MyScreen()
    }
}

The KoinApplication function will handle start & stop of your Koin context, regarding the cycle of the Compose context. This function start and stop a new Koin application context.

info

In an Android Application, the KoinApplication will handle any need to stop/restart Koin context regarding configuration changes or drop of Activities.

note

This replaces the use of the classic startKoin application function.

Starting over an existing Koin context​

Some time the startKoin function is already used in the application, to start Koin in your application (like in Android main app class, the Application class). In that case you need to inform your Compose application about the current Koin context with KoinContext or KoinAndroidContext. Those functions reuse current Koin context and bind it to the Compose application.

@Composable
fun App() {
    // Set current Koin instance to Compose context
    KoinContext() {

        MyScreen()
    }
}
info

Difference between KoinAndroidContext and KoinContext:

  • KoinAndroidContext is looking into current Android app context for Koin instance
  • KoinContext is looking into current GlobalContext for Koin instances
note

If you get some ClosedScopeException from a Composable, either use KoinContext on your Composable or ensure to have proper Koin start configuration with Android context

Compose Preview with Koin​

The KoinApplication function is interesting to start dedicated context for preview. This can be also used to help with Compose preview:

@Composable
@Preview
fun App() {
    KoinApplication(application = {
        // your preview config here
        modules(previewModule)
    }) {
        // Compose to preview with Koin
    }
}

Injecting into a @Composable​

While writing your composable function, you gain access to the following Koin API: koinInject(), to inject instance from Koin container

For a module that declares a 'MyService' component:

val androidModule = module {
    single { MyService() }
    // or constructor DSL
    singleOf(::MyService)
}

We can get your instance like that:

@Composable
fun App() {
    val myService = koinInject<MyService>()
}

To keep aligned on the functional aspect of Jetpack Compose, the best writing approach is to inject instances directly into functions parameters. This way allow to have default implementation with Koin, but keep open to inject instances how you want.

@Composable
fun App(myService: MyService = koinInject()) {

}

ViewModel for @Composable​

The same way you have access to classical single/factory instances, you gain access to the following Koin ViewModel API:

  • koinViewModel() - inject ViewModel instance
  • koinNavViewModel() - inject ViewModel instance + Navigation arguments data (if you are using Navigation API)

For a module that declares a 'MyViewModel' component:

module {
    viewModel { MyViewModel() }
    // or constructor DSL
    viewModelOf(::MyViewModel)
}

We can get your instance like that:

@Composable
fun App() {
    val vm = koinViewModel<MyViewModel>()
}

We can get your instance in function parameters:

@Composable
fun App(vm : MyViewModel = koinViewModel()) {

}
danger

Lazy API are not supported with updates of jetpack Compose

Module loading & unloading tied to Composable​

Koin offers you a way to load specific modules for a given Composable function. The rememberKoinModules function load Koin modules and remember on current Composable:

@Composable
@Preview
fun MyComponentComposable() {
    // load module at first call of this component
    rememberKoinModules(myModule)
}

You can use one of the abandon function, to unload module on 2 aspects:

  • onForgotten - after a composition is dropped out
  • onAbandoned - composition has failed

For this use unloadOnForgotten or unloadOnAbandoned argument for rememberKoinModules.

Creating Koin Scope with Composable​

The composable function rememberKoinScope and KoinScope allow to handle Koin Scope in a Composable, follow-up current to close scope once Composable is ended.

info

this API is still unstable for now