xamarin/Xamarin.Forms

[iOS] Dynamic cell content changes scroll position in CollectionView

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#7,195 opened on Aug 17, 2019

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a/collectionviewhelp wantedp/iOS 🍎partner/cat 😻s/unverifiedt/bug :bug:up-for-grabs

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Description

Description

Current implementation of cell resizing does not work properly. No idea if this is in any way related to #7128 or #7152.

We should probably create an automated test for this since we're now able to listen to scroll position changes through the Scrolled event.

Please also test this on Android in case the issue exists there as well.

Steps to Reproduce

  1. Run the Gallery app on a physical device (tested on XS)
  2. Go to CollectionView Gallery (enable CollectionView)
  3. Go to Item Size Galleries -> Expanding Text (Vertical List)
  4. Tap "More Text" on any item (ignore the first 3 items)
  5. Observe that as the cell height changes, scroll position changes as well
  6. Compare this functionality to Instagram (As you hit "more", scroll position never changes)
  7. If unable to reproduce, keep hitting "More Text" on other items until you see the issue.

Expected Behavior

Dynamic cell height should not move the cell up or down.

Actual Behavior

We lose current scroll position as cell height changes upon user action.

Contributor guide

Research direction
Inspect the CollectionView's layout behavior when cell heights change dynamically, focusing on scroll position management. Create an automated test using the Scrolled event to verify scroll position stability.
Tech stack
csharp
Domain
mobile
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Xamarin.FormsiOS developmentCollectionView
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75