fix: Android - Report - User is auto scrolled up after returning from second added receipt

[TaduJR]

Explanation of Change

That description is for the old fix (useRestoreScrollOnFocus). Your current fix is different it's the onScroll sync in index.android.tsx. The PR description needs to match the actual change. Here's an updated version:

Problem:
When the user is viewing a transaction thread (the expense detail page with the receipt), adds an attachment via the plus button, opens the just-added attachment, and presses back, the native FlatList restores a stale cached scroll position, jumping the user to a position further up in the list instead of staying at the bottom.

Root cause:
On Android, CustomFlatList saves the scroll offset in lastScrollOffsetRef to restore it when the screen is unfrozen (via useFocusEffect). However, this ref was only updated on onMomentumScrollEnd — which only fires after user-initiated fling gestures. Programmatic scrolls (like scrollToBottom() from scrollToBottomForCurrentUserAction) never trigger onMomentumScrollEnd, so lastScrollOffsetRef retains a stale high offset from the user's earlier scroll. When the screen regains focus, onScreenFocus restores this stale offset, scrolling the user up.

This was confirmed through extensive instrumentation: the onScreenFocus log showed RESTORING offset: 865 immediately after returning, even though scrollOffsetRef.current was 0 (bottom). The bug is Android-only because iOS uses native maintainVisibleContentPosition instead of manual save/restore.

Solution:
Intercept onScroll in CustomFlatList (Android) to keep lastScrollOffsetRef in sync with all scroll events both user-initiated and programmatic. This ensures onScreenFocus always restores the correct offset.

Fixed Issues

$ #84362
PROPOSAL:

Tests

Tests

Prerequisite: Account has at least one workspace.

Test Case 1:

1. Open any workspace chat
2. Create a manual expense
3. Open the just created expense
4. Add a receipt to the expense
5. After the receipt is added, return to report
6. Tap on the "Plus" button on receipt and add another receipt to report
7. Open the just added receipt and tap the back button to return to report
8. Verify you are not scrolled up after returning
9. Tap on the "Plus" button on receipt again and add another receipt
10. Open the just added receipt and tap the back button to return to report
11. Verify you remain at the bottom of the report (not auto-scrolled up)

Test Case 2:

1. Open Expense Report with enough messages to be scrollable
2. Send an attachment via the compose bar
3. Open the just-sent attachment
4. Press back to return to the report
5. Verify you remain at the bottom of the report

• Verify that no errors appear in the JS console

Offline tests

Same as tests

QA Steps

// TODO: These must be filled out, or the issue title must include "[No QA]."
Same as tests

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
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  • Android: Native
  • Android: mWeb Chrome
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• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
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    • If any non-english text was added/modified, I used JaimeGPT to get English > Spanish translation. I then posted it in #expensify-open-source and it was approved by an internal Expensify engineer. Link to Slack message:
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• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
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  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
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Screenshots/Videos

Android: Native

Android-Native.mp4

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

[melvin-bot]

@ahmedGaber93 Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

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Codecov Report

✅ Changes either increased or maintained existing code coverage, great job!

Files with missing lines	Coverage Δ
src/components/FlatList/FlatList/index.android.tsx	0.00% <0.00%> (ø)
... and 20 files with indirect coverage changes

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[JmillsExpensify]

LGTM though merge conflicts

[ahmedGaber93]

Reviewer Checklist

• I have verified the author checklist is complete (all boxes are checked off).
• I verified the correct issue is linked in the ### Fixed Issues section above
• I verified testing steps are clear and they cover the changes made in this PR
  • I verified the steps for local testing are in the Tests section
  • I verified the steps for Staging and/or Production testing are in the QA steps section
  • I verified the steps cover any possible failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
• I checked that screenshots or videos are included for tests on all platforms
• I included screenshots or videos for tests on all platforms
• I verified that the composer does not automatically focus or open the keyboard on mobile unless explicitly intended. This includes checking that returning the app from the background does not unexpectedly open the keyboard.
• I verified tests pass on all platforms & I tested again on:
  • Android: HybridApp
  • Android: mWeb Chrome
  • iOS: HybridApp
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• If there are any errors in the console that are unrelated to this PR, I either fixed them (preferred) or linked to where I reported them in Slack
• I verified proper code patterns were followed (see Reviewing the code)
  • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick).
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
  • I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
  • I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
  • I verified the JSDocs style guidelines (in STYLE.md) were followed
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I verified that this PR follows the guidelines as stated in the Review Guidelines
• I verified other components that can be impacted by these changes have been tested, and I retested again (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar have been tested & I retested again)
• I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
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• If any new file was added I verified that:
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  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG)
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
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• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
• For any bug fix or new feature in this PR, I verified that sufficient unit tests are included to prevent regressions in this flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
• I have checked off every checkbox in the PR reviewer checklist, including those that don't apply to this PR.

Screenshots/Videos

Android: HybridApp

20260331192626639.mp4

20260331192229672.mp4

Android: mWeb Chrome

iOS: HybridApp

iOS: mWeb Safari

MacOS: Chrome / Safari

[ahmedGaber93]

@TaduJR Are you able to reproduce the issue on the latest main? I am unable

Untitled.mp4

[TaduJR]

@TaduJR Are you able to reproduce the issue on the latest main? I am unable

Yes @ahmedGaber93

Still able to repo on latest main as of now.

Android-Native.mp4

[github-actions]

⚠️ This PR is possibly changing native code and/or updating libraries, it may cause problems with HybridApp. Please check if any patch updates are required in the HybridApp repo and run an AdHoc build to verify that HybridApp will not break. Ask Contributor Plus for help if you are not sure how to handle this. ⚠️

[TaduJR]

⚠️ This PR is possibly changing native code and/or updating libraries, it may cause problems with HybridApp. Please check if any patch updates are required in the HybridApp repo and run an AdHoc build to verify that HybridApp will not break. Ask Contributor Plus for help if you are not sure how to handle this. ⚠️

Please ignore this.

[ahmedGaber93]

@TaduJR I’m able to reproduce it now, but I need to manually scroll down and then back up first.

Your solution should work, but can we prevent it from scrolling up instead of forcing it to scroll down? It seems to behave correctly when scrolling manually, the issue only occurs after calling scrollToBottom.

[TaduJR]

Your solution should work, but can we prevent it from scrolling up instead of forcing it to scroll down? It seems to behave correctly when scrolling manually, the issue only occurs after calling scrollToBottom.

@ahmedGaber93

Sure, just pushed with this approach.

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[MelvinBot]

I reviewed the changes in this PR. The fix modifies CustomFlatList on Android (index.android.tsx) to keep the saved scroll offset in sync with all scroll events (not just momentum-based ones), preventing stale scroll position restoration when returning from an attachment.

No help site changes are required. This is an internal scroll-tracking bug fix with no impact on user-facing features, settings, workflows, or terminology documented in App/docs/articles.