Android library project - A Koin Application has already been started

Koin project used and used version:

• project: koin-android
• version: 2.0.1
• platform: Android

Bug Description

I am developing android-library project that uses Koin. The library should be used as a singleton and provides initialize method consuming Andorid Context in which Koin is initialized.

The library is initialized by user (let’s call it final app) in Application’s onCreate method.

It works as charm unless the final app uses Koin as well. In such case, the startKoin in android-library throws exception:

java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 
     Caused by: org.koin.core.error.InstanceCreationException: Could not create instance for [type:Single,primary_type:'my.example.project.core.LibraryInstance']
        at org.koin.core.instance.DefinitionInstance.create(DefinitionInstance.kt:61)
        at org.koin.core.instance.SingleDefinitionInstance.get(SingleDefinitionInstance.kt:40)
        at org.koin.core.definition.BeanDefinition.resolveInstance(BeanDefinition.kt:70)
        ... 
     Caused by: org.koin.core.error.KoinAppAlreadyStartedException: A Koin Application has already been started
        at org.koin.core.context.GlobalContext.start(GlobalContext.kt:51)
        at org.koin.core.context.GlobalContextKt.startKoin(GlobalContext.kt:71)
        at my.example.project.core.di.KoinContextProvider$koin$2.invoke(KoinContextProvider.kt:15)
        at my.example.project.core.di.KoinContextProvider$koin$2.invoke(KoinContextProvider.kt:10)
        at kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74)
        at my.example.project.core.di.KoinContextProvider.getKoin(KoinContextProvider.kt)
        at my.example.project.core.di.MyKoinComponent$DefaultImpls.getKoin(MyKoinComponent.kt:7)
        at my.example.project.core.LibraryInstanceImpl.getKoin(LibraryInstanceImpl.kt:14)
        at my.example.project.core.LibraryInstanceImpl.<init>(LibraryInstanceImpl.kt:74)
        at my.example.project.ExampleKoinApp$onCreate$1$1$1.invoke(ExampleKoinApp.kt:20)
        at my.example.project.ExampleKoinApp$onCreate$1$1$1.invoke(ExampleKoinApp.kt:11)

For sake of simplicity, the exception is a little shortened. I can provide full exception if necessary, but it seems like it is not allowed to call startKoin twice in an Android project?

Expected behavior

As basically any android-library can be using Koin in its internal implementation, shouldn’t it be independent and KoinApplication should be scoped?

To reproduce

1. Create an Android project with two modules - app and library
2. Configure koin-android dependency for both
3. Add implementation project(':library') in app’s build.gradle
4. In library project, create an object Library with method initialize consuming Android Context
5. In app project, extend Application class and in its onCreate method, startKoin and then call Library.initialize
6. The app should crash now

Support codes

class ExampleKoinApp : Application() {

    override fun onCreate() {
        super.onCreate()

        startKoin {
            androidContext(this@ExampleKoinApp)
            modules(...)
        }

        Library.initialize(this@ExampleKoinApp)
    }
}

object Library {

    private lateinit var appContext: Context

    val koin: Koin by lazy {
        startKoin {
            modules(...)
        }.koin
    }

    @Synchronized
    fun initialize(context: Context) {
        if (::appContext.isInitialized) return

        appContext = context.applicationContext
    }

[nikhil-thakkar]

You can’t call startKoin twice in the GlobalContext. You have two options:

1. Either use loadKoinModules
2. Use a KoinApplication to isolate your lib scope.

Both the approaches are documented well here.

[chrisnkrueger]

@hannesa2 Here is the new doc link: https://insert-koin.io/docs/3.1/reference/koin-core/context-isolation/