Fix Up Next scroll-to-top crash on long queues by joashrajin · Pull Request #5327 · Automattic/pocket-casts-android

joashrajin · 2026-05-22T05:25:58Z

Description

The following crash is something I could replicate:

Screen_Recording_20260521_131139_One.UI.Home.mp4

The lower "Up Next" button calls RecyclerView.quickScrollToTop(), which installs a LinearSmoothScroller whose calculateSpeedPerPixel computed:

val pixelsInRange = scrollRange * scrollOffset / scrollRange.toFloat()

The leading scrollRange * scrollOffset is Int * Int, evaluated before the divide-by-float. On long Up Next queues both values can be tens of thousands and their product overflows Int.MAX_VALUE, producing a negative pixelsInRange. That cascades into a negative speed-per-pixel, a negative duration handed to Action.update(…, duration, interpolator), and a fatal:

IllegalStateException: If you provide an interpolator, you must set a positive duration

The reporter's debug log confirms this path — the crash trace ends in a Choreographer frame callback dispatching a LinearSmoothScroller$Action.validate(), and the user had 332 episodes in Up Next at the time.

This PR:

Extracts the speed-per-pixel math into an internal top-level function so it can be unit-tested.
Replaces scrollRange * scrollOffset / scrollRange.toFloat() (mathematically equivalent to scrollOffset ignoring overflow) with scrollOffset.toFloat().coerceAtLeast(1f). The floor at 1f guarantees a positive speed (and therefore a positive duration), even if some future input falls outside the early-return guards.
Adds a unit test that exercises a scrollOffset × scrollRange combination that would have overflowed Int.MAX_VALUE under the old implementation.

Fixes PCDROID-417 (https://linear.app/a8c/issue/PCDROID-417/android-up-next-lower-button-causes-fatal-crash)

Testing Instructions

Build and install the app.
Add ~20+ episodes to the Up Next queue (enough that the queue scrolls past a screenful).
Open the player, then open Up Next via the lower "Up Next" button (the one with the text label, not the badge button).
Scroll down through the queue for 5+ seconds so a large scrollOffset accumulates.
Tap the lower "Up Next" button again.
- Verify the queue smoothly scrolls back to the top with no crash.
- Repeat a few times to confirm the crash never reappears.
- Tap the lower "Up Next" button while already at the top — verify nothing breaks (regression check).

The new RecyclerViewTest also exercises the math directly:

./gradlew :modules:services:views:testDebugUnitTest --tests "au.com.shiftyjelly.pocketcasts.views.extensions.RecyclerViewTest"

Screenshots or Screencast

N/A — bug fix, no UI changes.

Checklist

If this is a user-facing change, I have added an entry in CHANGELOG.md
Ensure the linter passes (./gradlew spotlessApply to automatically apply formatting/linting)
I have considered whether it makes sense to add tests for my changes
All strings that need to be localized are in modules/services/localization/src/main/res/values/strings.xml (n/a)
Any jetpack compose components I added or changed are covered by compose previews (n/a)
I have updated (or requested that someone edit) the spreadsheet to reflect any new or changed analytics. (n/a)

The smooth scroller in quickScrollToTop computed pixelsInRange as scrollRange * scrollOffset / scrollRange.toFloat(). The leading Int * Int multiplication can overflow on long lists, producing a negative value that propagates into LinearSmoothScroller as a negative duration and crashes with IllegalStateException: "If you provide an interpolator, you must set a positive duration". The formula simplifies to scrollOffset; use Float math directly and floor to 1 to guarantee a positive speed.

Extract the speed-per-pixel math out of the anonymous LinearSmoothScroller so it can be unit-tested without Android dependencies, and cover the Int-overflow case that triggered the original crash.

dangermattic · 2026-05-22T05:26:31Z

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Pull request overview

Fixes a crash in the “Up Next” screen’s scroll-to-top behavior on long queues by preventing integer overflow from producing a negative smooth-scroller duration.

Changes:

Refactors RecyclerView.quickScrollToTop() speed calculation into an internal helper (quickScrollSpeedPerPixel) and removes the overflow-prone intermediate multiplication.
Ensures speed-per-pixel stays positive via float math (and a >= 1f floor), preventing LinearSmoothScroller from receiving a non-positive duration.
Adds unit tests covering edge cases (non-positive inputs, overflow regime) and updates the changelog.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
modules/services/views/src/main/java/au/com/shiftyjelly/pocketcasts/views/extensions/RecyclerView.kt	Replaces overflow-prone speed math with a safe helper and fallbacks to `super` when inputs are invalid.
modules/services/views/src/test/java/au/com/shiftyjelly/pocketcasts/views/extensions/RecyclerViewTest.kt	Adds unit tests validating positive speed output and guarding edge/overflow cases.
CHANGELOG.md	Documents the crash fix under 8.13 Bug Fixes.

joashrajin · 2026-05-25T11:27:56Z

@copilot resolve the merge conflicts in this pull request

Co-authored-by: joashrajin <16253818+joashrajin@users.noreply.github.com>

Copilot · 2026-05-25T11:31:38Z

@copilot resolve the merge conflicts in this pull request

Resolved — I merged origin/main into this branch and fixed the conflict in CHANGELOG.md in commit e3baea45.

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- Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED --add-opens=java.base/java.time=ALL-UNNAMED -Xmx8048M -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp /home/REDACTED/.gradle/wrapper/dists/gradle-9.5.1-bin/iq79hdu3mqx29lgffhp8bfmx/gradle-9.5.1/lib/gradle-daemon-main-9.5.1.jar (dns block)

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joashrajin · 2026-05-25T19:08:33Z

@copilot resolve the merge conflicts in this pull request

joashrajin · 2026-05-25T19:09:37Z

@geekygecko / @sztomek I can confirm the crash no longer appears on debug. I'll get a recording done tomorrow

Co-authored-by: joashrajin <16253818+joashrajin@users.noreply.github.com>

Copilot · 2026-05-25T19:10:43Z

@copilot resolve the merge conflicts in this pull request

Resolved — I merged the latest origin/main and fixed the CHANGELOG.md conflict in commit d344acd.

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I tried to connect to the following addresses, but was blocked by firewall rules:

dl.google.com
- Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED --add-opens=java.base/java.time=ALL-UNNAMED -Xmx8048M -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp /home/REDACTED/.gradle/wrapper/dists/gradle-9.5.1-bin/iq79hdu3mqx29lgffhp8bfmx/gradle-9.5.1/lib/gradle-daemon-main-9.5.1.jar (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

joashrajin · 2026-05-26T15:51:50Z

Screen.Capture.on.2026-05-26.at.17-49-06.mp4

8.11 vs debug build ^

joashrajin added 3 commits May 21, 2026 12:27

Add test for quickScrollToTop speed calc and CHANGELOG entry

b74a4c4

Extract the speed-per-pixel math out of the anonymous LinearSmoothScroller so it can be unit-tested without Android dependencies, and cover the Int-overflow case that triggered the original crash.

Update CHANGELOG with PR link

1a02b84

joashrajin requested a review from a team as a code owner May 22, 2026 05:25

joashrajin requested review from Copilot and sztomek and removed request for a team May 22, 2026 05:25

Copilot started reviewing on behalf of joashrajin May 22, 2026 05:26 View session

joashrajin mentioned this pull request May 22, 2026

Fix Up Next scroll-to-top crash on long queues #5320

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Copilot AI reviewed May 22, 2026

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joashrajin added [Type] Bug Not functioning as intended. [Area] Up Next labels May 22, 2026

joashrajin self-assigned this May 25, 2026

Copilot started work on behalf of joashrajin May 25, 2026 11:28 View session

Merge origin/main and resolve CHANGELOG conflict

e3baea4

Co-authored-by: joashrajin <16253818+joashrajin@users.noreply.github.com>

Copilot finished work on behalf of joashrajin May 25, 2026 11:32

Copilot started work on behalf of joashrajin May 25, 2026 19:08 View session

Merge origin/main and resolve CHANGELOG conflict

d344acd

Co-authored-by: joashrajin <16253818+joashrajin@users.noreply.github.com>

Copilot AI review requested due to automatic review settings May 25, 2026 19:10

joashrajin review requested due to automatic review settings May 25, 2026 19:10

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Fix Up Next scroll-to-top crash on long queues#5327

Fix Up Next scroll-to-top crash on long queues#5327
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Description

Testing Instructions

Screenshots or Screencast

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