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:
Flow<T>.collectWhileResumedIn(LifecycleOwner)
Flow<T>.collectWhileResumed(LifecycleOwner, suspend (T) -> Unit)
The other two are for collecting Flow<T>
while LifecycleOwner
is in STARTED
state:
Flow<T>.collectWhileStartedIn(LifecycleOwner)
Flow<T>.collectWhileStarted(LifecycleOwner, suspend (T) -> Unit)
Those functions collect the flow and:
- Destroy its collection job on LifecycleOwner's
onPause()
(collectWhileResumed
/collectWhileResumedIn
) oronStop()
(collectWhileStarted
/collectWhileStartedIn
). - Recreates its collection job on LifecycleOwner's
onResume()
(collectWhileResumed
/collectWhileResumedIn
) oronStart()
(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.
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 */
}
}
}