flowWithLifecycle(lifecycle, Lifecycle.State.STARTED) doesn't stop flows while App is in background

Question

I'm trying to observe the result of the View Collection and upstream flows stopped. But viewModel.testFlow is still collecting while the App is in the background. Why can't I observe the collection is stopped? Am I observing something wrong?

ViewModel:

val testFlow = flow<Int> {
    for (i in 1..100) {
        delay(1000)
        Timber.e("testFlow: EMIT = $i")
        emit(i)
    }
}

Activity:

override fun onViewCreated() {
        lifecycleScope.launch {
            viewModel.testFlow
                .flowWithLifecycle(lifecycle, Lifecycle.State.STARTED)
                .collect {
                    Timber.d("testFlow: $it Collected")
                }
        }
}

override fun onActivityPaused(activity: Activity) {
    super.onActivityPaused(activity)
    Timber.e("testFlow: onActivityPaused")
}

https://medium.com/androiddevelopers/a-safer-way-to-collect-flows-from-android-uis-23080b1f8bda

Hungnam

Where did you get the lifecycle variable for your flowWithLifecycle? – Prana

Answer 1

You are using Lifecycle.State.STARTED state to start observing Flow, the corresponding method of the Activity when emission stops is onStop(). If onStop() method of Activity is called the emission and collecting will stop.

If you want to stop emitting and collection data when onPause method is called, you can use Lifecycle.State.RESUMED state.

When app goes to background onStop() method of Activity is called and when using Lifecycle.State.STARTED state to observe the Flow you should see the emission and collecting stop.

Swithbert

Answer 2

you can handle another way with repeatOnLifecycle

lifecycleScope.launch {
        repeatOnLifecycle(Lifecycle.State.STARTED){
            viewModel.stateLocationPermission.collect() {
                handleStateLocationPermission(it)
            }
        }
    }

Moneybag

Answer 3

You can make use of this extension:

fun <T> Flow<T>.collectLifecycleAware(
    owner: LifecycleOwner,
    flowCollector: FlowCollector<T>,
) {
    owner.lifecycleScope.launch {
        [email protected](owner.lifecycle)
            .collect(flowCollector)
    }
}

And use it as:

state.collectLifecycleAware(viewLifecycleOwner) { state ->
    ...
}

Also, you'll need:

implementation "androidx.lifecycle:lifecycle-runtime-ktx:<latest-version>"

Sanctum