Delegates

class MainActivity : AppCompatActivity(), StateLogger by StateLoggerImpl(), ActionBarHandler by ActionbarHandlerImpl() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        registerLifecycleOwner(this)
        setActionbar(actionBar)
        setContentView(R.layout.activity_main)
    }
}

interface StateLogger {
    fun registerLifecycleOwner(lifecycleOwner: LifecycleOwner)
}

interface ActionBarHandler {
    fun setActionbar(toolbar: ActionBar?)
}

class StateLoggerImpl: StateLogger, LifecycleEventObserver {

    override fun registerLifecycleOwner(lifecycleOwner: LifecycleOwner) {
        lifecycleOwner.lifecycle.addObserver(this)
    }

    override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
        Log.d(TAG, "State is : ${event.name}")
    }

    fun sendStateEvent(state: String) {
        Log.d(TAG, "State is : $state")
    }
}

class ActionbarHandlerImpl: ActionBarHandler {

    private var mActionbar: ActionBar? = null

    override fun setActionbar(actionBar: ActionBar?) {
        mActionbar = actionBar
        initToolbar()
    }

    private fun initToolbar() {
        mActionbar?.setLogo(R.drawable.ic_launcher_background)
        mActionbar?.title = "SampleTitle"
    }

    fun setTitle(title: String) {
        mActionbar?.title = title
    }
}