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 APIkoin-androidx-compose-navigation
- Compose ViewModel API with Navigation API integration
for an Android/Multiplatform app, use the following packages:
koin-compose
- Compose base APIkoin-compose-viewmodel
- Compose ViewModel APIkoin-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:
fun koinConfiguration() = koinApplication {
// your configuration & modules here
modules(...)
}
@Composable
fun App() {
KoinApplication(::koinConfiguration) {
// 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.
In an Android Application, the KoinApplication
will handle any need to stop/restart Koin context regarding configuration changes or drop of Activities.
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()
}
}
Difference between KoinAndroidContext
and KoinContext
:
KoinAndroidContext
is looking into current Android app context for Koin instanceKoinContext
is looking into current GlobalContext for Koin instances
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 instancekoinNavViewModel()
- inject ViewModel instance + Navigation arguments data (if you are usingNavigation
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()) {
}
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.
this API is still unstable for now