Activity, Fragment & Service as KoinComponents.kt

Activity, Fragment & Service as KoinComponents
Activity, Fragment & Service are extended with the KoinComponents extension. You gain access to:

by inject() - lazy evaluated instance from Koin container
get() - eager fetch instance from Koin container
release() - release module’s instances from its path
getProperty()/setProperty() - get/set property


val androidModule = module {
    // a factory of Presenter
    factory { Presenter() }
}



class DetailActivity : AppCompatActivity() {

    // Lazy injected Presenter instance
    override val presenter : Presenter by inject()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // ...
    }
  
  
  

injection_parameters.kt

In any single, factory or scoped definition,
you can use injection parameters:
parameters that will be injected and used by your definition:

val presenter : Presenter by inject { parametersOf(view) }

class Presenter(val view : View)

val myModule = module {
    single{ (view : View) -> Presenter(view) }
}

invesigate_koin.kt

Loading after start
After Koin has been started with startKoin { } function, 
it is possible to load extra definitions modules with the following function: 
loadKoinModules(modules...)

val myModule = module {

    // Will match type ServiceImp only
    single { ServiceImp() }

    // Will match type Service only
    single { ServiceImp() as Service }

}

val myModule = module {

    // Will match type ServiceImp only
    single { ServiceImp() }

    // Will match type Service only
    single { ServiceImp() as Service }

}

scop_activity.kt

module {
    // declare a scope for MyActivity
    scope(named<MyActivity>()) {
        scoped { MyPresenter() }
    }
}


class MyActivity : AppCompatActivity {
    
    // get presenter from current scope
    val presenter : MyPresenter by currentScope.inject()
}

class MyFragment : Fragment() {

    override fun onViewCreated(...) {

        // get Presenter instance from Activity's scope
        val presenter : MyPresenter  by lazy { activity?.currentScope.get() }
    }
}

Taming the Android lifecycle.kt

Taming the Android lifecycle

Android components are mainly managed by their lifecycle: we can’t directly instantiate an Activity nor a Fragment. 
The system make all creation and management for us, and make callbacks on methods: onCreate, onStart…

That’s why we can’t describe our Activity/Fragment/Service in a Koin module


In the case of MVP architecture style, the Presenter is a short live component to help/support the UI.
The presenter must be created each time the screen is showing, and dropped once the screen is gone.