From 305249f9642da50bf680b1401644eaba9d5dce50 Mon Sep 17 00:00:00 2001 From: Samuel Susla Date: Thu, 25 Apr 2024 09:20:42 -0700 Subject: [PATCH] maintain correct content offset when scroll view is suspended (#44256) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/44256 [iOS] [Fixed] - Preserve content offset in ScrollView when the component is suspended On iOS, components are recycled. For ScrollView, its content offset has to be reset back to original position. When we call `[UIScrollView setContentOffset:]`, it triggers all of its delegate methods and triggers `scrollViewDidScroll` where we set native state. So when user scrolls to position 100 and scroll view suspends. it is removed from view hierarchy and recycled. Once the suspense boundary is resolved, scroll view will be inserted back into view hierarchy. But when it was recycled, we set back its original content offset (the default is 0, 0) but this was accidentally propagated through to shadow tree. To avoid this, we simply need to invalidate `_state` before calling `[UIScrollView setContentOffset:]`. Reviewed By: cipolleschi Differential Revision: D56573370 fbshipit-source-id: c03d7d2d403af2e1649b4cf189072baeb4c286c8 --- .../ComponentViews/ScrollView/RCTScrollViewComponentView.mm | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm b/packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm index 90a9a134dcea72..24e256a09d3602 100644 --- a/packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm +++ b/packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm @@ -420,6 +420,11 @@ - (void)_updateStateWithContentOffset - (void)prepareForRecycle { + [super prepareForRecycle]; + // Must invalidate state before setting contentOffset on ScrollView. + // Otherwise the state will be propagated to shadow tree. + _state.reset(); + const auto &props = static_cast(*_props); _scrollView.contentOffset = RCTCGPointFromPoint(props.contentOffset); // We set the default behavior to "never" so that iOS @@ -427,7 +432,6 @@ - (void)prepareForRecycle // and keeps it as an opt-in behavior. _scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever; _shouldUpdateContentInsetAdjustmentBehavior = YES; - _state.reset(); _isUserTriggeredScrolling = NO; CGRect oldFrame = self.frame; self.frame = CGRectZero;