MainActivityDagger.kt

class MainActivity : AppCompatActivity() {

    @Inject
    lateinit var greetingService: GreetingService

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        (application as DaggerApplication).appComponent.inject(this)

        val greetings = findViewById<TextView>(R.id.greetingsTextView)
        greetings.text = "${greetingService.greetings()}"
    }
}