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Start Koin on Android

docs/reference/koin-android/start.md

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The koin-android project is dedicated to provide Koin powers to Android world. See the Android setup section for more details.

From your Application class

From your Application class you can use the startKoin function and inject the Android context with androidContext as follows:

kotlin
class MainApplication : Application() {

    override fun onCreate() {
        super.onCreate()

        startKoin {
            // Log Koin into Android logger
            androidLogger()
            // Reference Android context
            androidContext(this@MainApplication)
            // Load modules
            modules(myAppModules)
        }
    }
}

:::info You can also start Koin from anywhere if you don't want to start it from your Application class. :::

If you need to start Koin from another Android class, you can use the startKoin function and provide your Android Context instance with just like:

kotlin
startKoin {
    //inject Android context
    androidContext(/* your android context */)
    // ...
}

Start Koin with Annotations

When using Koin Annotations, you can use startKoin<T>() to start Koin with your annotated module class:

kotlin
@KoinApplication
class MainApplication : Application() {

    override fun onCreate() {
        super.onCreate()

        startKoin<MainApplication> {
            androidLogger()
            androidContext(this@MainApplication)
        }
    }
}

The startKoin<T>() function automatically loads the generated module from your @Module annotated class.

For multiple modules:

kotlin
@Module
@Configuration
@ComponentScan("com.myapp.data")
class DataModule

@Module
@Configuration
@ComponentScan("com.myapp.domain")
class DomainModule

@KoinApplication
class MainApplication

// Start with multiple modules
startKoin<MainApplication> {
    androidLogger()
    androidContext(this@MainApplication)
}

Extra Configurations

From your Koin configuration (in startKoin { } block code), you can also configure several parts of Koin.

Koin Logging for Android

Within your KoinApplication instance, we have an extension androidLogger which uses the AndroidLogger() class. This logger is an Android implementation of the Koin logger.

Up to you to change this logger if it doesn't suit to your needs.

kotlin
startKoin {
    // use Android logger - Level.INFO by default
    androidLogger()
    // ...
}

Loading Properties

You can use Koin properties in the assets/koin.properties file, to store keys/values:

kotlin
startKoin {
    // ...
    // use properties from assets/koin.properties
    androidFileProperties()   
}

Start Koin with AndroidX Startup (4.0.1)

AndroidX Startup is a library that provides a straightforward way to initialize components at app startup. It uses a single ContentProvider to initialize all dependencies, avoiding the overhead of separate ContentProviders for each component that needs early initialization.

By using Gradle package koin-androidx-startup, we can use KoinStartup interface to declare your Koin configuration in your Application class:

kotlin
class MainApplication : Application(), KoinStartup {

     override fun onKoinStartup() = koinConfiguration {
        androidContext(this@MainApplication)
        modules(appModule)
    }

    override fun onCreate() {
        super.onCreate()
    }
}

This replaces the startKoin function that is usally used in onCreate. The koinConfiguration function is returning a KoinConfiguration instance.

:::info KoinStartup integrates with AndroidX App Startup to initialize Koin via ContentProvider before Application.onCreate(). This is useful when you need to manage initialization order with other Initializers that depend on Koin being available. :::

:::warning KoinStartup runs on the main thread during app startup. If you're not using AndroidX App Startup library to manage other Initializers, there is no benefit to using KoinStartup - use the standard startKoin approach instead. For dispatching module loading to background threads, see Lazy Modules. :::

If you have other Initializers that need Koin, make them depend on KoinInitializer:

kotlin
class CrashTrackerInitializer : Initializer<Unit>, KoinComponent {
    private val crashTrackerService: CrashTrackerService by inject()

    override fun create(context: Context) {
        crashTrackerService.configure(context)
    }

    override fun dependencies(): List<Class<out Initializer<*>>> {
        return listOf(KoinInitializer::class.java)
    }
}

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