leecade/react-native-swiper

Loop={true} + initialIndex leads to brief off by one error flicker

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#1.003 geöffnet am 30. Juni 2019

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component: ViewPagerhelp wanted🐛bug🔎investigate

Beschreibung

Which OS ?

iOS

Version

1.6

  • react-native-swiper v1.6
  • react-native v0.59.8

Expected behaviour

I was debugging an issue where setting the index param briefly showed the wrong data (off by one earlier) for a brief second before a redraw happened.

In debugging, this seems to be related to the loop={true} behavior (the default), since eliminating looping causes the offset to be calculated correctly and no flicker.

I'm guessing the implementation has some kind of 'extra' item at the front to handle the left-swipe when looping, and the initialOffset is not accounting for this?

Actual behaviour

Setting index causes it to start drawing on the correct position without a flicker.

Steps to reproduce

  1. Create a Swiper with multiple items, and loop={true}
  2. Set the initial index.
  3. Observe that it is briefly off by one before correcting itself.

Contributor Guide

Tech Stack
javascriptreact native
Domain
mobile
Issue Type
bug
SchwierigkeitGeschätzte Implementierungsschwierigkeit für neue Contributors, von 1 für sehr kleine Änderungen bis 5 für Expertenarbeit.
3
Geschätzte ZeitEin grober Zeitrahmen, um zu recherchieren, zu implementieren, zu testen und einen Pull Request vorzubereiten.
1-2 days
AktivitätsstatusWie verfügbar das Issue gerade wirkt: frisch, aktiv, stale, blockiert oder wartet auf Maintainer-Input.
stale
KlarheitWie klar das Issue die erwartete Änderung, Akzeptanzkriterien und den nächsten Schritt erklärt.
mostly clear
Voraussetzungen
React Native basicsUnderstanding of swiper component logic
EinsteigerfreundlichkeitEin Score von 1 bis 100, der schätzt, wie zugänglich dieses Issue für First-Time Contributors ist.
40
Research-Richtung
Investigate the offset calculation logic in the Swiper component when loop is enabled. Examine how initialIndex is applied and whether an extra placeholder item causes the initial offset to be miscalculated. Compare with non loop behavior where no flicker occurs. Look at the source file, likely Swiper.js, and trace the initialOffset setup. Check comments in the issue for any hints from maintainers.