Flow - lightweight architecture article -

MainActivity.kt

@AndroidEntryPoint
class MainActivity : AppCompatActivity(), SharedPreferences.OnSharedPreferenceChangeListener {
    ...

    // Data store from which to receive location updates via Flow, injected via Hilt
    @Inject
    lateinit var repository: LocationRepository

    // Get a reference to the Job from the Flow so we can stop it from UI events
    private var locationFlow: Job? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        ...
        button.setOnClickListener {
            val tracking = SharedPreferenceUtil.getLocationTrackingPref(this);
            if (!tracking) {
                subscribeToLocationUpdates()
            } else {
                unsubscribeToLocationUpdates()
            }
        }
    }

    private fun subscribeToLocationUpdates() {
        // Observe locations via Flow as they are generated by the repository
        locationFlow = repository.getLocations()
            .flowWithLifecycle(lifecycle, Lifecycle.State.STARTED)
            .onEach {
                logResultsToScreen("Foreground location: ${it.toText()}")
            }
            .launchIn(lifecycleScope)

        foregroundOnlyLocationService?.subscribeToLocationUpdates()
    }

    private fun unsubscribeToLocationUpdates() {
        locationFlow?.cancel()
        foregroundOnlyLocationService?.unsubscribeToLocationUpdates()
    }
    ...
}