xamarin/Xamarin.Forms

[Bug] CollectionView with itemtemplate selector and bindable layout behaves strangely on iOS

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#7,799 opened on Oct 3, 2019

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4.3.0a/collectionviewe/4 :clock4:help wantedi/regressionp/iOS 🍎t/bug :bug:up-for-grabs

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Description

Description

I have a CollectionView where you can add either a simple int or a List of objects with ItemTemplate set to a selector. I have a bindable StackLayout with a selector in one of the templates on the CollectionView. On adding items the CollectionView behaves strangely, refreshes and places new items in the middle of the list. Only broken in iOS, android fine.

Steps to Reproduce

  1. Open repro.
  2. Click AddModel and Add SImple alternately until page full.
  3. Scroll to bottom.
  4. CollectionView refreshes on adding items.

Expected Behavior

CollectionView adds items to bottom of list.

Actual Behavior

CollectionView refreshes and adds items to middle temporarily, and starts overlapping items.

Basic Information

  • Version with issue :4.3.0.851321-pre3
  • Last known good version: In 4.2 just freezes once screen is full or all the items disappear.
  • IDE: Visual Studio 2019 16.3.2
  • Platform Target Frameworks:
    • iOS: 13.0
  • Affected Devices: iPhone 8 simulator

Screenshots

2019-10-03_03-47-05-PM

Reproduction Link

CollectionViewTemplateSelectors.zip

Contributor guide

Research direction
Inspect the CollectionView layout updates when using ItemTemplate selector with BindableLayout on iOS. Focus on the RefreshView behavior and item insertion order.
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.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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.Forms
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65