This is my AppComponent Interface

FxAppComponent

import dagger.BindsInstance
import dagger.Subcomponent
import javafx.application.Application
import javafx.fxml.FXMLLoader
import javafx.stage.Stage
import java.net.URL
import java.util.*
import java.util.function.Function

@FxAppScoped
@Subcomponent(modules = [FxAppModule::class])
interface FxAppComponent {
    fun fxmlLoaderFactory(): Function<URL, FXMLLoader>

    fun loader(fxmlUrl: URL): FXMLLoader {
        return fxmlLoaderFactory().apply(Objects.requireNonNull(fxmlUrl))
    }

    @Subcomponent.Builder
    interface Builder {

        @BindsInstance
        fun application(application: Application): Builder

        @BindsInstance
        fun mainWindow(mainWindow: Stage?): Builder

        fun build(): FxAppComponent
    }
}