IssueTracker

Yigit, do you have time to fix it?

reemission of the same liveData is racy

yea i'll take it.

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.

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()
        }
    }

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)

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} )
        }

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

Just to clarify, how should I go about integrating TransitionManager.beginDelayedTransition(mToolbar); with AndroidX Navigation?

Never mind, I got it to work using this code:

        Toolbar appBar = findViewById(R.id.toolbar);
        setSupportActionBar(appBar);

        // Hook up the app bar with the navigation
        navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        NavigationUI.setupActionBarWithNavController(this, navController);
        navController.addOnDestinationChangedListener((controller, destination, arguments) -> TransitionManager.beginDelayedTransition(appBar));

Thanks for your help!

Ian - is it worth adding this somewhere in the navigation module docs?

NavigationUI is the one triggering the change in app icons, so we'll add the code on our side.

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

commit e28e8678478c7c04b55886e7071750cbdea89121
Author: jbwoods <jbwoods@google.com>
Date:   Thu Jun 27 14:32:13 2019

    Animate Toolbar Changes in NavigationUI
   
    When animateLayoutChanges is set on a Toolbar, there are errors in how
    the text within the toolbar is displayed if it has an arrow. The text
    leaves a big space on destinations with no arrow.
   
    This change checks so see if the icon will be null and then uses a
    TransitionManager to animate the toolbar text into the proper position.
    We only animate when the icon is going to disappear. If we were animate
    when the icon is appearing, the new icon and text appear stacked when
    the animation begins.
   
    Test: Tested visually in app
    BUG: 131403621
    Change-Id: I97ff213bdeb6da3282287d9b572f33c74cf9e9e7

M       navigation/navigation-ui/build.gradle
M       navigation/navigation-ui/src/main/java/androidx/navigation/ui/CollapsingToolbarOnDestinationChangedListener.java
M       navigation/navigation-ui/src/main/java/androidx/navigation/ui/ToolbarOnDestinationChangedListener.java

https://android-review.googlesource.com/1007867
https://goto.google.com/android-sha1/e28e8678478c7c04b55886e7071750cbdea89121

This has been fixed internally and will be available in the Navigation 2.1.0-beta01 release.