Make it easier to react to Lifecycle State changes in Compose [235529345]

Fixed

Feature Request

Status Update

No update yet.

Description

il...@google.com

created issue #1

Jun 9, 2022 11:56PM

Component used: Lifecycle

Version used: 2.5.0-rc01

Reacting to a Lifecycle.State changes is currently fairly complicated in a Jetpack Compose based app, requiring a DisposableEffect based approach with registering a LifecycleObserver with the LocalLifecycleOwner.

Ideally, this would come in two forms:

I'd like to see a way to capture the current Lifecycle.State as State, perhaps something like LocalLifecycleOwner.current.lifecycle.currentStateFlow.collectAsState()
I'd like a way to run side effects when the Lifecycle changes, perhaps using a custom LifecycleEventEffect that would only run the effect when the Lifecycle.State changes.

Comments

il...@google.com <il...@google.com> Sep 13, 2022 12:14AM

Assigned to sa...@google.com.

tr...@gmail.com <tr...@gmail.com> #2Oct 26, 2022 07:14AM

Yigit, do you have time to fix it?

reemission of the same liveData is racy

a....@gmail.com <a....@gmail.com> #3Nov 4, 2022 10:30PM

yea i'll take it.

sj...@gmail.com <sj...@gmail.com> #4Feb 23, 2023 07:56AM

Thanks for the detailed analysis. This may not be an issue anymore since we've started using Main.immediate there but I' not sure; I'll try to create a test case.

sj...@gmail.com <sj...@gmail.com> #5Mar 7, 2023 11:30AM

just emitting same live data reproduces the issue.

@Test
fun raceTest() {
val subLiveData = MutableLiveData(1)
val subject = liveData(testScope.coroutineContext) {
emitSource(subLiveData)
emitSource(subLiveData) //crashes
}
subject.addObserver().apply {
testScope.advanceUntilIdle()
}
}

sa...@google.com <sa...@google.com> Mar 14, 2023 08:18PM

Accepted by sa...@google.com.

ap...@google.com <ap...@google.com> #6Mar 16, 2023 07:03PM

With 2.2.0-alpha04 (that use Main.immediate), the issue seems to be still there (I tested it by calling emitSource() twice, like your test case)

lm...@gmail.com <lm...@gmail.com> #7Mar 22, 2023 05:51PM

yea sorry immediate does not fix it.
I actually have a WIP fix for it:

https://android-review.googlesource.com/c/platform/frameworks/support/+/1112186

if your case is the one i found (emitting same LiveData multiple times, as shown in #5) you can work around it by adding a dummy transformation.

val subLiveData = MutableLiveData(1)
val subject = liveData(testScope.coroutineContext) {
emitSource(subLiveData.map {it })
emitSource(subLiveData.map {it} )
}

lm...@gmail.com <lm...@gmail.com> #8Mar 22, 2023 05:51PM

Project: platform/frameworks/support
Branch: androidx-master-dev

commit af12e75e6b4110f48e44ca121466943909de8f06
Author: Yigit Boyar <yboyar@google.com>
Date: Tue Sep 03 12:58:11 2019

Fix coroutine livedata race condition

This CL fixes a bug in liveData builder where emitting same
LiveData source twice would make it crash because the second
emission registry could possibly happen before first one is
removed as source.

We fix it by using a suspending dispose function. It does feel
a bit hacky but we cannot make DisposableHandle.dispose async
and we do not want to block there. This does not mean that there
is a problem if developer disposes it manually since our emit
functions take care of making sure it disposes (and there is
no other way to add source to the underlying MediatorLiveData)

Bug: 140249349
Test: BuildLiveDataTest#raceTest_*

Change-Id: I0b464c242a583da4669af195cf2504e2adc4de40

M lifecycle/lifecycle-livedata-ktx/api/2.2.0-alpha05.txt
M lifecycle/lifecycle-livedata-ktx/api/current.txt
M lifecycle/lifecycle-livedata-ktx/api/public_plus_experimental_2.2.0-alpha05.txt
M lifecycle/lifecycle-livedata-ktx/api/public_plus_experimental_current.txt
M lifecycle/lifecycle-livedata-ktx/api/restricted_2.2.0-alpha05.txt
M lifecycle/lifecycle-livedata-ktx/api/restricted_current.txt
M lifecycle/lifecycle-livedata-ktx/src/main/java/androidx/lifecycle/CoroutineLiveData.kt
M lifecycle/lifecycle-livedata-ktx/src/test/java/androidx/lifecycle/BuildLiveDataTest.kt

https://android-review.googlesource.com/1112186

https://goto.google.com/android-sha1/af12e75e6b4110f48e44ca121466943909de8f06

lm...@gmail.com <lm...@gmail.com> #9Mar 22, 2023 05:51PM

في الأربعاء، 22 مارس، 2023 8:51 م جابر لمعي <lmyj6520@gmail.com> كتب:

- Show quoted text -

ap...@google.com <ap...@google.com> #10May 2, 2023 10:39PM

Project: platform/frameworks/support
Branch: androidx-main

commit e9afa3a28b32897fef6717fea079c6296f3a2e5a
Author: sanura <sanura@google.com>
Date: Tue Apr 25 01:07:17 2023

Create LifecycleEventEffect composable

Adding LifecycleEventEffect composable API to
be used when running SideEffects based on a
particular Lifecycle.Event.

RelNote: "`LifecycleEventEffect` API has been
added to run side effects based on `Lifecycle.Event`."
Test: LifecycleEventEffectTest
Bug: 235529345

Change-Id: Ic9794d7e59b1a66cc7f31cbaebed9b3d3dee5dd3

M lifecycle/lifecycle-runtime-compose/api/current.txt
M lifecycle/lifecycle-runtime-compose/api/public_plus_experimental_current.txt
M lifecycle/lifecycle-runtime-compose/api/restricted_current.txt
M lifecycle/lifecycle-runtime-compose/src/androidTest/java/androidx/lifecycle/compose/CollectAsStateWithLifecycleTests.kt
A lifecycle/lifecycle-runtime-compose/src/androidTest/java/androidx/lifecycle/compose/LifecycleEffectTest.kt
M lifecycle/lifecycle-runtime-compose/src/androidTest/java/androidx/lifecycle/compose/LifecycleExtTest.kt
A lifecycle/lifecycle-runtime-compose/src/main/java/androidx/lifecycle/compose/LifecycleEffect.kt

https://android-review.googlesource.com/2560450

ap...@google.com <ap...@google.com> #11May 4, 2023 10:09PM

Project: platform/frameworks/support
Branch: androidx-main

commit 25a2002ab933ea551295483aa3f7e278d60dbe75
Author: sanura <sanura@google.com>
Date: Wed May 03 20:20:56 2023

Create LifecycleResumeEffect composable

Adding LifecycleResumeEffect composable API to be used when
running SideEffects based on ON_RESUME/ON_PAUSE event callbacks.

RelNote: "`LifecycleResumeEffect` API has been added to run side
effects based on both `Lifecycle.Event.ON_RESUME` and
`Lifecycle.Event.ON_PAUSE` event callbacks."
Test: lifecycleResumeEffectTest
Bug: 235529345

Change-Id: I603860f21eb6a433c909d7ae6f8120f6d23179aa

M lifecycle/lifecycle-runtime-compose/api/current.txt
M lifecycle/lifecycle-runtime-compose/api/public_plus_experimental_current.txt
M lifecycle/lifecycle-runtime-compose/api/restricted_current.txt
M lifecycle/lifecycle-runtime-compose/src/androidTest/java/androidx/lifecycle/compose/LifecycleEffectTest.kt
M lifecycle/lifecycle-runtime-compose/src/main/java/androidx/lifecycle/compose/LifecycleEffect.kt

https://android-review.googlesource.com/2577033

ap...@google.com <ap...@google.com> #12May 4, 2023 10:09PM

Project: platform/frameworks/support
Branch: androidx-main

commit 2b090a54b8182927eb0e96062e0a14d065a8561a
Author: sanura <sanura@google.com>
Date: Tue May 02 19:53:55 2023

Create LifecycleStartEffect composable

Adding LifecycleStartEffect composable API to be used when
running SideEffects based on ON_START/ON_STOP event callbacks.

RelNote: "`LifecycleStartEffect` API has been added to run side
effects based on `Lifecycle.Event.ON_START` and
`Lifecycle.Event.ON_STOP` event callbacks."
Test: lifecycleStartEffectTest
Bug: 235529345

Change-Id: I5a8d1e6f152b7083e086146ba97044c4b454db84

M lifecycle/lifecycle-runtime-compose/api/current.txt
M lifecycle/lifecycle-runtime-compose/api/public_plus_experimental_current.txt
M lifecycle/lifecycle-runtime-compose/api/restricted_current.txt
M lifecycle/lifecycle-runtime-compose/src/androidTest/java/androidx/lifecycle/compose/LifecycleEffectTest.kt
M lifecycle/lifecycle-runtime-compose/src/main/java/androidx/lifecycle/compose/LifecycleEffect.kt

https://android-review.googlesource.com/2576490

st...@gmail.com <st...@gmail.com> #13May 29, 2023 02:24PM

Is there a target API version where this may be released?

il...@google.com <il...@google.com> #14May 30, 2023 10:58PM

This is still in progress for inclusion in Lifecycle 2.7.0-alpha01.

ap...@google.com <ap...@google.com> #15Jun 1, 2023 11:36PM

Project: platform/frameworks/support
Branch: androidx-main

commit ad273fa4882a38a5a2f72004044ce3173b2c06a9
Author: sanura <sanura@google.com>
Date: Fri May 05 02:02:59 2023

Add samples for LifecycleEffects

Adding samples for LifecycleEventEffect,
LifecycleStartEffect, and LifecycleResumeEffect.

RelNote: "All composables in `LifecycleEffect` now
link sample usages."
Test: ./gradlew bOS
Bug: 235529345

Change-Id: Ib4786f4b586cf9390f3dbe6f3b0fc86c60267a86

M lifecycle/lifecycle-runtime-compose/samples/src/main/java/androidx/lifecycle/compose/samples/LifecycleComposeSamples.kt
M lifecycle/lifecycle-runtime-compose/src/main/java/androidx/lifecycle/compose/LifecycleEffect.kt

https://android-review.googlesource.com/2579164

sa...@google.com <sa...@google.com> Jun 21, 2023 07:39PM

Marked as fixed.

lm...@gmail.com <lm...@gmail.com> #16Jun 22, 2023 04:31AM

فخاامه

في الأربعاء، 21 يونيو، 2023 10:40 م <buganizer-system@google.com> كتب:

- Show quoted text -

ka...@gmail.com <ka...@gmail.com> #17Jul 7, 2023 08:12AM

When will this be released?

na...@google.com <na...@google.com> #18Jul 26, 2023 05:21PM

The following release(s) address this bug.It is possible this bug has only been partially addressed:

androidx.lifecycle:lifecycle-runtime-compose:2.7.0-alpha01

sj...@gmail.com <sj...@gmail.com> #19Jan 11, 2024 06:40AM

Just want to say that Lifecycle 2.7.0 stable has been finally released. Thank you very much 🙏🏼

ey...@gmail.com <ey...@gmail.com> #20Jan 11, 2024 02:10PM

I'm getting some strange results from `currentStateFlow` as opposed to setting a regular lifecycle observer. Basically, for ON_PAUSE and ON_STOP I get STARTED and CREATED, respectively.

jb...@google.com <jb...@google.com> #21Jan 11, 2024 02:20PM

Yes, those are the Lifecycle.States that reflect those particular Lifecycle.Events. Please take a look at the Lifecycle guidance for more details.

ey...@gmail.com <ey...@gmail.com> #22Jan 11, 2024 03:21PM

Sorry, my bad, didn't realize that. But since this is a flow, shouldn't it emit events rather than states? What is the usecase to react to two states that never become invalid? The docs claim this is in order to "read changes in the lifecycle" but it would require further processing to be able to realize what's going on.

jb...@google.com <jb...@google.com> #23Jan 11, 2024 04:32PM

Receiving a state from the flow would be the signal that a change has occurred and the new state is that particular change. There are cases where you don't care how you get to a state, just that you are there. We also offer LifecycleEffects to assist with use cases for Lifecycle.Events.

il...@google.com <il...@google.com> #24Jan 11, 2024 05:31PM

If you look at the release notes, you'll find two separate sections - one on Lifecycle Events (where you can use Lifecycle.asFlow() to get a Flow of Lifecycle.Event) and one for Lifecycle State (where you can use Lifecycle.currentStateFlow to get the current Lifecycle.State).

Make sure you are using the right API.

ey...@gmail.com <ey...@gmail.com> #25Jan 12, 2024 09:20AM

Thank you both for all the guidance. I guess my issue is that I'm trying to use it outside of Compose, to replace a simple lifecycle event observer, since it just feels like a nicer interface to collect a flow. For Compose, the effects work fine, indeed.

il...@google.com <il...@google.com> #26Jan 16, 2024 08:25PM

Lifecycle.asFlow() works outside of Compose too and gives you Lifecycle.Event instances as they occur. That's why that API exists separately from currentStateFlow.