[BLOG] Example of Fragment handling ViewModel's ViewState and Interactions

SettingsFragment.kt

class SettingsFragment : Fragment() {

    private val viewModel: SettingsViewModel2 by viewModels()

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        setInteractions()
        observeViewState()
    }

    private fun setInteractions() {
        notificationsSwitch.setOnCheckedChangeListener { checked ->
            viewModel.onInteraction(NotificationSwitchChanged(checked))
        }
        notificationsButton.setOnClickListener {
            viewModel.onInteraction(NotificationSettingButtonClick)
        }

        /* other interactions */
    }

    private fun observeViewState() {
        viewModel.viewState.observe(viewLifecycleOwner, Observer { viewState ->
            render(viewState ?: return@Observer)
        })
    }

    private fun render(viewState: ViewState) {
        renderName(viewState)
        renderNotifications(viewState)
    }

    private fun renderName(viewState: ViewState) {
        firstNameText.text = viewState.firstName
        lastNameText.text = viewState.lastName
    }

    private fun renderNotifications(viewState: ViewState) {
        notificationzSwitch.isChecked = viewState.notificationsChecked
        notificationsButton.isEnabled = viewState.notificationsEnabled
    }
}