Removal of visible item may result in showing an unexpected item [154124815]

Fixed

Bug

Status Update

No update yet.

Description

je...@google.com

created issue #1

Apr 15, 2020 06:07PM

When items are same size as the viewport, and RV is currently laid out such that the viewport shows exactly one complete item, and you remove that item from the dataset, it can't find a reference child that is in the viewport. It defaults to using the first child it found in the hierarchy (getChild(0) for regular LTR RVs) as the reference child. But then it doesn't seem to use that child's old position as the anchor position, but just places that child at the start of the viewport.

That is a problem if you are looking at the last item (item N) and have two extra items laid out before the visible one. You'd expect that if you remove item N, you will look at item N-1 after that. But, it will actually go to item N-2.

I didn't check the behavior if you're not looking at the last item, but that might be affected as well.

Comments

sh...@google.com <sh...@google.com> #2Apr 15, 2020 10:09PM

Proposed solution: aosp/1286717

So far, I didn't look at any code other than this local code... but given the logical assumptions that must be made by callers who use this code... this solution should suffice. Will look a bit deeper before this solution gets submitted.

sh...@google.com <sh...@google.com> #3Apr 15, 2020 10:09PM

Reassigned to je...@google.com.

Jelle, take a look and tell me what you think.

sh...@google.com <sh...@google.com> #4Apr 15, 2020 10:11PM

Took a bit of a closer look, and yeah... this approach seems right in principle (didn't look to closely to make sure my implementation suggestion was actually correct).

je...@google.com <je...@google.com> #5Apr 16, 2020 09:40AM

Yes, this seems like a working solution. I have some doubts if we shouldn't address the way the anchor info is updated or used given a reference child, but at the same time I think that is a rabbit hole we should avoid. So I'm in favor of your solution :)

ap...@google.com <ap...@google.com> #6May 4, 2020 11:13PM

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

commit fe867028214a364167c893083065eddcd709e223
Author: Shep Shapard <shepshapard@google.com>
Date: Wed Apr 15 14:02:59 2020

Improve out of bounds anchor.

Bug fixes involve a behavior change where
if all in bounds children are removed from a
LinearLayoutManager, and out of bounds children
are found to become potential anchors, out of bounds
children that are "further down in the scroll direction"
are moved to fill in the RV.

Bug: 154124815
Test: ./gradlew recyclerview:recyclerview:connectedCheck --info --daemon -Pandroid.testInstrumentationRunnerArguments.class=androidx.recyclerview.widget.LinearLayoutManagerRemoveShownItemsTest

Change-Id: I63b177d1bedd8016125bc6aa619fb12714797252

M recyclerview/recyclerview/src/androidTest/java/androidx/recyclerview/widget/LinearLayoutManagerFindReferenceChildTest.kt
M recyclerview/recyclerview/src/androidTest/java/androidx/recyclerview/widget/LinearLayoutManagerFindZeroPxReferenceChildTest.kt
A recyclerview/recyclerview/src/androidTest/java/androidx/recyclerview/widget/LinearLayoutManagerRemoveShownItemsTest.kt
M recyclerview/recyclerview/src/main/java/androidx/recyclerview/widget/GridLayoutManager.java
M recyclerview/recyclerview/src/main/java/androidx/recyclerview/widget/LinearLayoutManager.java
M samples/Support7Demos/src/main/AndroidManifest.xml
A samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/RemoveLargeItemsDemo.java
A samples/Support7Demos/src/main/res/layout/remove_large_items_demo.xml
A samples/Support7Demos/src/main/res/layout/remove_large_items_demo_item.xml

https://android-review.googlesource.com/1286717

sh...@google.com <sh...@google.com> May 8, 2020 08:40PM

Marked as fixed.

ch...@gmail.com <ch...@gmail.com> #7Jan 6, 2021 04:13PM

i think this bug doesn't fix. when i clear the mainAdapter and then update footerAdapter, sometimes it will jump to the bottom