meliorence / meliorence/react-native-snap-carousel
useState in onSnapToItem breaks item display
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Description
Is this a bug report, a feature request, or a question?
Bug report.
Have you followed the required steps before opening a bug report?
(Check the step you've followed - put an x character between the square brackets ([]).)
- I have read the guidelines regarding bug report.
- I have reviewed the documentation in its entirety, including the dedicated documentations 📚.
- I have searched for existing issues and made sure that the problem hasn't already been reported.
- I am using the latest plugin version.
- I am following the issue template closely in order to produce a useful bug report.
Have you made sure that it wasn't a React Native bug?
Yes, it is an explicit react-native-snap-carousel bug
Is the bug specific to iOS or Android? Or can it be reproduced on both platforms?
It is reproducible in Snack on iOS, iOS 12.2
Is the bug reproductible in a production environment (not a debug one)?
Yes
Environment
Environment:
React: 16.8.3
React native: 0.59.2
react-native-snap-carousel: 3.8.0
Target Platform:
iOS (12.2)
Expected Behavior
While snapping between items, the active item would appear bigger.
Actual Behavior
While using
onScroll={Animated.event([{
nativeEvent: { contentOffset: { x: scrollValue.current } },
}])}
with Animated in order to interpolate colors for custom indicator
and also onSnapToItem with hooks calls inside, the snapped item where hooks were called become permanently inactive in terms of bigger display.
Removing onScroll or hooks from onSnapToItem fixes the issue, but I need both methods.

Reproducible Demo
(Paste the link to a Snack example in which the issue can be reproduced. Please follow the guidelines for providing a Minimal, Complete, and Verifiable example.)
Steps to Reproduce
(Write your steps so that anyone can reproduce the issue in the Snack demo you provided.)
- Open the Snack
- Swipe right, the back
- Done< the bug is here
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running the linked Snack demo with the reported onScroll Animated.event and onSnapToItem hook usage, then reproduce the swipe-right-and-back sequence. Compare behavior with onScroll or the hooks removed; done means the snapped active item still displays larger while both behaviors remain enabled.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, react-native
- Domain
- mobile
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100