Dat Vu
1.8 KiB
0075. Fix load more not triggered on iOS when fast scrolling to bottom
Date: 2026-03-31
Status
Context
On iOS, handleLoadMoreEmailsRequest() was never triggered when users scrolled to the bottom of the email list. The original condition used exact equality:
scrollInfo.metrics.pixels == scrollInfo.metrics.maxScrollExtent
Root cause: iOS uses BouncingScrollPhysics (spring-based simulation), which causes pixels to either overshoot or settle slightly short of maxScrollExtent depending on scroll speed and device performance. In both cases, ScrollEndNotification fires when pixels != maxScrollExtent, so the condition is never satisfied.
This behavior is device-dependent — newer/faster devices (iPhone 13 Pro Max, iOS 18) are less affected, while older/slower devices (iPhone 7, iOS 15) exhibit larger deviations. Android is unaffected because ClampingScrollPhysics clamps pixels exactly within [0, maxScrollExtent].
Decision
Apply ClampingScrollPhysics on iOS only, and replace == with >=:
// physics
physics: PlatformInfo.isIOS
? const ClampingScrollPhysics()
: const AlwaysScrollableScrollPhysics(),
// condition
scrollInfo.metrics.pixels >= scrollInfo.metrics.maxScrollExtent
ClampingScrollPhysics ensures pixels is clamped exactly to maxScrollExtent at the boundary, making the condition deterministic. The >= adds a defensive guard for any residual edge cases.
Consequences
- Load more works correctly across all iOS versions and device generations.
- No behavior change on Android or Web.
- iOS loses the native bounce feel at list boundaries. Acceptable for an email list UI.
- No risk of duplicate requests due to the existing
isRunningguard.