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maintain correct content offset when scroll view is suspended (#44256)

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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
This commit is contained in:
Samuel Susla
2024-05-01 18:15:01 +01:00
committed by Riccardo Cipolleschi
parent 3467f2f3a3
commit 305249f964
1 changed files with 5 additions and 1 deletions
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packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm
+5 -1
View File
@@ -420,6 +420,11 @@ static void RCTSendScrollEventForNativeAnimations_DEPRECATED(UIScrollView *scrol
- (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<const ScrollViewProps &>(*_props);
_scrollView.contentOffset = RCTCGPointFromPoint(props.contentOffset);
// We set the default behavior to "never" so that iOS
@@ -427,7 +432,6 @@ static void RCTSendScrollEventForNativeAnimations_DEPRECATED(UIScrollView *scrol
// and keeps it as an opt-in behavior.
_scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
_shouldUpdateContentInsetAdjustmentBehavior = YES;
_state.reset();
_isUserTriggeredScrolling = NO;
CGRect oldFrame = self.frame;
self.frame = CGRectZero;