"Page must be 0 when pageCount is 0" thrown when pageCount > 0

[zoltish]

Describe the bug

Scrolling through a HorizontalPager throws this exception in rare cases, Ive seen 3 crash logs in a group of about 1000 users. The pager always shows a fixed list that never changes. I believe the issue is triggered by recompositions happening while scrolling the pager.

Environment:

• Android OS version: [Android 7 & 9]
• Device: [Emulated Nexus 5 & Huawei P10]
• Accompanist version: [0.21.1-beta]

[cristianbtg]

I saw this happening starting v0.19.0 when a configuration change happened (e.g. language) where during recomposition the pageCount and currentPage were set to 0, even though I was using the rememberPagerState().

Before v0.19.0 PagerState.Saver was saving pageCount and currentPage and it was working fine; currently it's only saving pageCount, but from my observation, during the first recomposition it's 0 so it might lead to some crashes.

[aazizbekyan]

The workaround for time being:

    LaunchedEffect(pagerState.pageCount) {
        if (pagerState.pageCount != 0) {
             // now interact with pagerState
        }
    }

[andkulikov]

Can you show the crash stacktrace?

[zoltish]

Sorry, Ive switched crash reporting tools since my post and I no longer have access to it. I guess the good news is that I havent seen it since then in a group of 5000 users. Ill let you know if it pops up again!

[yschimke]

I've hit a tangential bug.

I can define initialPage to either of my two pages.

    val pagerState = rememberPagerState(initialPage = 0)

If in a launched effect I want to update the initial page or scroll to a page, then I can only do that once the composable has rendered. Which would be the scrollToPage case.

This means I can update the initial page once by launched effect completes.

[yschimke]

Never mind, I think I can just move my LaunchedEffect inside to where I have already created the HorizontalPager.

[yasanglass]

This is the most common crash on my Compose app, I just started handling it by just checking the page count.

@andkulikov I use Firebase Crashlytics so I do have the crash log:

Fatal Exception: java.lang.IllegalArgumentException: page must be 0 when pageCount is 0
at com.google.accompanist.pager.PagerState.requireCurrentPage(PagerState.java:1)
at com.google.accompanist.pager.PagerState.animateScrollToPage$default(PagerState.java:26)
at yasan.space.mnml.ai.launcher.ui.main.MainActivity$HandleGlobalEvents$1$1.invokeSuspend(MainActivity.java:26)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(BaseContinuationImpl.java:2)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.java:86)
at androidx.compose.ui.platform.AndroidUiDispatcher.performTrampolineDispatch(AndroidUiDispatcher.java:1)
at androidx.compose.ui.platform.AndroidUiDispatcher$dispatchCallback$1.run(AndroidUiDispatcher.java:2)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:236)
at android.app.ActivityThread.main(ActivityThread.java:7864)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:620)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1011)

arch_disk_io_0
at sun.misc.Unsafe.park(Unsafe.java)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:190)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2067)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1092)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1152)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:923)

pool-4-thread-1
at sun.misc.Unsafe.park(Unsafe.java)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:190)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2067)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1120)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:849)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1092)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1152)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:923)

pool-14-thread-1
at sun.misc.Unsafe.park(Unsafe.java)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:190)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2067)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1092)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1152)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:923)

I can send the rest if you want as well.

[dbobrzyk]

@andkulikov PagerState also crashes on version accompanist = "0.17.0"

Fatal Exception: java.lang.IllegalArgumentException
page must be 0 when pageCount is 0
com.google.accompanist.pager.PagerState.requireCurrentPage (PagerState.kt:656)
com.google.accompanist.pager.PagerState.updateLayoutPages (PagerState.kt:486)
com.google.accompanist.pager.PagerState.setPageCount (PagerState.java:221)
com.google.accompanist.pager.PagerStateKt.rememberPagerState (PagerState.kt:81)

[andkulikov]

@dbobrzyk

Please try to upgrade to the latest version before reporting any bugs - https://github.com/google/accompanist/releases

[3laeddine-dh]

I cant Solve it . Any Solution !!

[yasanglass]

I cant Solve it . Any Solution !!

@3laeddine-dh Just check the page size before changing the current page:

if (pagerState.pageCount != 0) pagerState.animateScrollToPage(MyPages.TargetPage)

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days.

[dbobrzyk]

@dbobrzyk

Please try to upgrade to the latest version before reporting any bugs - https://github.com/google/accompanist/releases

After updating to version 0.23.0 issue is still present.

[wakaztahir]

I am using latest version v0.24.6-alpha , It crashes when I try to scroll to page , even when the content has been rendered completely , and in fact , the page count is always 0
So I have a button and I press it and it crashes right away !

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.z7apps.familytracker, PID: 18730
    java.lang.IllegalArgumentException: page must be 0 when pageCount is 0
        at com.google.accompanist.pager.PagerState.requireCurrentPage(PagerState.kt:328)
        at com.google.accompanist.pager.PagerState.animateScrollToPage(PagerState.kt:201)
        at com.google.accompanist.pager.PagerState.animateScrollToPage$default(PagerState.kt:197)
        at com.z7apps.familytracker.ui.setup.SetupScreenKt$PermissionsSetup$1$2$1.invokeSuspend(SetupScreen.kt:88)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
        at androidx.compose.ui.platform.AndroidUiDispatcher.performTrampolineDispatch(AndroidUiDispatcher.android.kt:81)
        at androidx.compose.ui.platform.AndroidUiDispatcher.access$performTrampolineDispatch(AndroidUiDispatcher.android.kt:41)
        at androidx.compose.ui.platform.AndroidUiDispatcher$dispatchCallback$1.run(AndroidUiDispatcher.android.kt:57)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:240)
        at android.app.ActivityThread.main(ActivityThread.java:7829)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:512)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1027)

[arbyruns]

I was able to solve this by adding state = pagerState to HorizontalPager. So something like this

val pagerState = rememberPagerState()

HorizontalPager(count = 10, state = pagerState) { page ->
...
}

[undermark5]

@arbyruns This was fixed by #1195, which is included as of https://github.com/google/accompanist/releases/tag/v0.24.11-rc. If you can update the library, to that version or newer, this is no longer an issue.