LimitOffsetPagingSource loads partial initial page when near bottom of the list causing ui jump [389729367]

Fixed

Bug

Status Update

No update yet.

Description

ev...@tatarka.me

created issue #1

Jan 13, 2025 10:17PM

Component used: room, room-paging Version used: 2.7.0-alpha12 Devices/Android versions reproduced on: emulator

Steps to reproduce:

Scroll to the end of the list. Then preform a refresh that reduces the number of items in the database but keeps the last items that are visible.
Note the ui jumps up several items. This is is because the first load is smaller than the screen size.

This appears to be caused by the logic in https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:room/room-paging/src/commonMain/kotlin/androidx/room/paging/util/RoomPagingUtil.kt;drc=6d0e4120b9ea66164e1f3c1d93e711fac2aed847;l=76 specifically, if the refresh key lands within the last page it'll load fewer items than expected.

Changing

if (key >= itemCount) {
    maxOf(0, itemCount - params.loadSize)
} else {
    key
}

if (key >= itemCount - params.loadSize) {
    maxOf(0, itemCount - params.loadSize)
} else {
    key
}

should fix it.

Comments

da...@google.com <da...@google.com> Jan 15, 2025 05:25PM

Reassigned to da...@google.com.

ap...@google.com <ap...@google.com> #2Jan 15, 2025 07:49PM

Marked as fixed.

Project: platform/frameworks/support
Branch: androidx-main
Author: Eva <eva@tatarka.me>
Link: https://android-review.googlesource.com/3452628

[GH] room-paging refresh initial load fix

Expand for full commit details

[GH] room-paging refresh initial load fix 
 
## Proposed Changes 
 
If items are removed then the initial key for a refresh may be close enough to the end of the list that fewer than a screens-worth of items may be loaded causing the UI to jump. Changed to handle similarly to the case where the initial key larger than itemCount and load loadSize items from the end. 
 
## Testing 
 
Test: ./gradlew test connectedCheck 
 
## Issues Fixed 
 
Fixes: b/389729367 
 
This is an imported pull request from https://github.com/androidx/androidx/pull/750. 
 
Resolves #750 
Github-Pr-Head-Sha: e01574c59eaeb92cffd0cd1606b213b7fc5af475 
GitOrigin-RevId: a6c2d92a4012757817fd74af4fc1a57fb6de8f88 
Change-Id: I2abbe92633bf95aa3306e4c2ebc47eacebfffa8c

Files:

M room/integration-tests/kotlintestapp/src/androidTest/java/androidx/room/integration/kotlintestapp/test/MultiTypedPagingSourceTest.kt
M room/room-paging/src/androidInstrumentedTest/kotlin/androidx/room/paging/LimitOffsetPagingSourceTest.kt
M room/room-paging/src/commonMain/kotlin/androidx/room/paging/util/RoomPagingUtil.kt

Hash: 79ddb7ed533cc8808a3ae3c52d36cb3f5ef0602b
Date: Tue Jan 14 08:04:43 2025

na...@google.com <na...@google.com> #3Jan 29, 2025 06:11PM

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

androidx.room:room-paging:2.7.0-alpha13
androidx.room:room-paging-android:2.7.0-alpha13
androidx.room:room-paging-iosarm64:2.7.0-alpha13
androidx.room:room-paging-iossimulatorarm64:2.7.0-alpha13
androidx.room:room-paging-iosx64:2.7.0-alpha13
androidx.room:room-paging-jvm:2.7.0-alpha13
androidx.room:room-paging-linuxarm64:2.7.0-alpha13
androidx.room:room-paging-linuxx64:2.7.0-alpha13
androidx.room:room-paging-macosarm64:2.7.0-alpha13
androidx.room:room-paging-macosx64:2.7.0-alpha13

Issue 389729367

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Comments

da...@google.com <da...@google.com> Jan 15, 2025 05:25PM

ap...@google.com <ap...@google.com> #2Jan 15, 2025 07:49PM

na...@google.com <na...@google.com> #3Jan 29, 2025 06:11PM

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