Android Share Data Between Activity and Fragment Using ViewModel

class ParentActivity : AppCompatActivity() {    lateinit var viewModel: QuoteMakerXViewModel    override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)        setContentView(R.layout.parent)        setSupportActionBar(toolbar)        viewModel = ViewModelProviders.of(this).get(ParentViewModel::class.java)        viewModel.testMessage = "Hello"        viewModel.selectItemEvent.observe(this, Observer { event ->            Timber.d("selectItemEvent=$event")        })        viewModel.sharedLiveData.observe(this, Observer { event ->            Timber.d("sharedLiveData=$event")        })    }}

class ParentViewModel : ViewModel() {    internal val selectItemEvent = SingleLiveEvent<String>()    internal val sharedLiveData = MutableLiveData<String>()    internal var testMessage: String? = null}

class ChildAFragment : Fragment() {    override fun onCreateView(        inflater: LayoutInflater, container: ViewGroup?,        savedInstanceState: Bundle?    ): View? {        // Inflate the layout for this fragment        return inflater.inflate(R.layout.childa, container, false)    }    override fun onActivityCreated(savedInstanceState: Bundle?) {        super.onActivityCreated(savedInstanceState)        viewModel = ViewModelProviders.of(activity!!).get(ParentViewModel::class.java)        // shared message from parent        Timber.d("viewModel.testMessage=%s", viewModel.testMessage)        // send ui event back to parent        button.setOnClickListener {            viewModel.selectItemEvent.value = "ChildA button click"        }        // send data back to parent        viewModel.sharedLiveData.value = "ChildA loaded"    }}