Sending events to UI with Channel/Flow + custom collector (see my first comment for reasons behind it)

Sending events to UI.kt

/**
 * Starts collecting a flow when the lifecycle is started, and **cancels** the collection on stop.
 * This is different from `lifecycleScope.launchWhenStarted { flow.collect{...} }`, in which case
 * the coroutine is just suspended on stop.
 */
inline fun <reified T> Flow<T>.collectWhileStarted(
    lifecycleOwner: LifecycleOwner,
    noinline action: suspend (T) -> Unit
) {
    object : DefaultLifecycleObserver {
        private var job: Job? = null

        init {
            lifecycleOwner.lifecycle.addObserver(this)
        }

        override fun onStart(owner: LifecycleOwner) {
            job = owner.lifecycleScope.launch {
                collect { action(it) }
            }
        }

        override fun onStop(owner: LifecycleOwner) {
            job?.cancel()
            job = null
        }
    }
}


class MyViewModel : ViewModel() {
    // You can specify exact buffer size and onBufferOverflow strategy here, or go full blast with Channel.UNLIMITED
    private val eventChannel = Channel<String>(capacity = 10, onBufferOverflow = BufferOverflow.DROP_OLDEST)
    val eventFlow = eventChannel.receiveAsFlow()
    fun sendEvent(element: String) = eventChannel.trySend(element)  // `trySend` replaces `offer` since Coroutines 1.5
}


class MyFragment : Fragment(R.layout.fragment_my) {
    private val viewModel: MyViewModel by viewModels()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // You can collect flow in `onCreate` using `this` as lifecycleOwner
        // This is a bit more efficient: `LifecycleObserver` is registered only once
        viewModel.eventFlow.collectWhileStarted(this) { Log.i(TAG, "event: $it") }
    }

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

        // Or you can collect flow in `onViewCreated` using `viewLifecycleOwner`
        // This more closely resembles a typical LiveData observer
        viewModel.eventFlow.collectWhileStarted(viewLifecycleOwner) { Log.i(TAG, "event: $it") }
    }
}

BTW, one phrase caught my eye: "business logic remains the same for the same app on different mobile platforms". Is Google starting to push us towards KMP? ;)

In 2024, your expectations are materializing.

https://android-developers.googleblog.com/2024/05/android-support-for-kotlin-multiplatform-to-share-business-logic-across-mobile-web-server-desktop.html