Important Note

Google's library androidx.lifecycle:lifecycle-runtime-ktx:2.4.0-alpha01 introduced three new APIs that fullfil the same use cases of flow-lifecycle-observer, and probably more: LifecycleOwner.addRepeatingJob, Lifecycle.repeatOnLifecycle, and Flow.flowWithLifecycle. You can check this Medium post and the official documentation for more information.

flow-lifecycle-observer

This library provides four Flow<T> extension functions for collecting flows in a lifecycle-aware manner.

Two of the extensions functions are for collecting Flow<T> while LifecycleOwner is in RESUMED state:

1. Flow<T>.collectWhileResumedIn(LifecycleOwner)
2. Flow<T>.collectWhileResumed(LifecycleOwner, suspend (T) -> Unit)

The other two are for collecting Flow<T> while LifecycleOwner is in STARTED state:

3. Flow<T>.collectWhileStartedIn(LifecycleOwner)
4. Flow<T>.collectWhileStarted(LifecycleOwner, suspend (T) -> Unit)

Those functions collect the flow and:

1. Destroy its collection job on LifecycleOwner's onPause() (collectWhileResumed/collectWhileResumedIn) or onStop() (collectWhileStarted/collectWhileStartedIn).
2. Recreates its collection job on LifecycleOwner's onResume() (collectWhileResumed/collectWhileResumedIn) or onStart() (collectWhileStarted/collectWhileStartedIn).

Motivation

The main motivation for this library is to have lifecycle-aware collectors much like those that can be launched with:

lifecycleScope.launchWhenStarted {
    flow.collect { }
}

The issue with the above approach is that if our flow is a SharedFlow<T>, paused collectors will still be subscribed collectors, so they will have no effect on SharedFlow's SharingStarted.WhileSubscribed() and SharedFlow<T>.subscriptionCount configurations.

Read more on https://proandroiddev.com/should-we-choose-kotlins-stateflow-or-sharedflow-to-substitute-for-android-s-livedata-2d69f2bd6fa5?source=activity---post_recommended_rollup

Installation

On project-level build.gradle, add Jitpack repository:

allprojects {
  repositories {
    maven { url 'https://jitpack.io' }
  }
}

On app-level build.gradle, add dependency:

dependencies {
    implementation 'com.github.psteiger:flow-lifecycle-observer:0.2.1'
}

Usage

@AndroidEntryPoint
class NearbyUsersActivity : AppCompatActivity() {
    
    private val viewModel: NearbyUsersViewModel by viewModels()
    
    override fun onCreate(savedInstanceState: Bundle?) {
        viewModel
            .locations
            .onEach { /* new locations received */ }
            .collectWhileStartedIn(this)
            
        viewModel
            .users
            .collectWhileStarted(this) {
                /* new users received */
            }
    }
}