Dagger.kt

@Singleton
@Component(
    modules = [
        AppModule::class
    ]
)
interface AppComponent {
    fun inject(activity: MainActivity)
}

@Module
class AppModule {
    @Provides
    fun provideUser(): User {
        return User.getInstance()
    }
}

class MyApplication : Application {
    lateinit var appComponent: AppComponent

    override fun onCreate() {
        super.onCreate()
        DaggerAppComponent.builder()
            .build()
    }
}

class MainActivity : Activity {
    @Inject
    lateinit var initUser: User

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        (application as MyApplication).appComponent.inject(this)

        // You can manipulate initUser here
    }
}