Compose scrollables should keep their focused children in view when the scrollable area is resized [216842427]

Fixed

Bug

Status Update

No update yet.

Description

kl...@google.com

created issue #1

Jan 28, 2022 09:26PM

This is how ScrollView works. Modifier.focusable does already call BringIntoViewRequester.bringIntoView(), but that doesn't work if the focusable is already in view request is made, but a scrollable parent resizes afterwards (as in the case when the keyboard is shown after a small delay).

See design doc.

Comments

kl...@google.com <kl...@google.com> Jan 28, 2022 09:27PM

Accepted by kl...@google.com.

kl...@google.com <kl...@google.com> #2Jan 31, 2022 07:08PM

I was able to reproduce the issue. It is broken since

https://android-review.googlesource.com/c/platform/frameworks/support/+/1686519.
I don't think there is any workaround available so I recommend for everyone affected to stay on beta06 for a bit.

ap...@google.com <ap...@google.com> #3Feb 2, 2022 09:51PM

Take this with a huge grain of salt but I had the same/similar issue occasionally on beta06 and before as well. It got a lot worse with beta07. Just scrolling and randomly finding items that are not rendered whatsoever. I'm developing deeply nested dynamic forms so I could be hitting multiple edge cases or perhaps made a mistake myself but I don't have these issues with a verticalScroll modifier on a regular column.

ap...@google.com <ap...@google.com> #4Feb 23, 2022 08:47PM

I localised the issue and indeed looks like similar situation could be reproduced even before beta07, just not so often. Especially it was possible if you emit multiple layouts per item of LazyColumn. I am working on the fix.

ap...@google.com <ap...@google.com> #5Feb 24, 2022 09:23PM

Found a temporary workaround

Instead of your current:

LazyColumn {
    items(myList) {
        MyItem(it)
    }
}

LazyColumn {
    itemsIndexed(myList) { index, it ->
        key(index) { // TODO remove key() after upgrade to beta08
            MyItem(it)
        }
    }
}

ap...@google.com <ap...@google.com> #6Mar 7, 2022 11:55PM

Marked as fixed.

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

commit a3b566102eb60c3396dfae0dd5ea57e8eb15f0a1
Author: Andrey Kulikov <andreykulikov@google.com>
Date: Thu May 20 20:57:53 2021

Fix for LazyColumn/Row items displayed partially after the scroll

It was the old issue with how we handle not placed children which became often reproducible after introducing slots reuse in LazyColumn. When the layout was not placing its children node remeasuring and redrawing for such node and its children was skipped as this node is not visible. Once this node was becoming visible again we weren't correctly restoring the node's sub-hierarchy. Now we correctly reschedule remeasurings and redrawings for the dirty nodes for the whole subtree.

Relnote: Fixed the bug introduced in beta07 where LazyColumn/Row items were displayed partially after the scroll
Test: InvalidatingNotPlacedChildTest
Bug: 188566058
Change-Id: I8c9ac2df59f3183bf6067dd20092a127f16c9e80

M compose/ui/ui/src/androidAndroidTest/kotlin/androidx/compose/ui/draw/InvalidatingNotPlacedChildTest.kt
M compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/node/LayoutNode.kt
M compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/node/LayoutNodeWrapper.kt
M compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/node/LayoutTreeConsistencyChecker.kt

https://android-review.googlesource.com/1713858

Issue 216842427