[CollectionView] CollectionView Expands to full screen with FlexLayout

[HobDev]

Description

I have developed a screen for an app. When FlexLayout is the Content of the ContentPage the CollectionView expand to whole screen. Whereas when StackLayout is the Content of the ContentPage the CollectionView takes remaining space after adjusting all other views.

Steps to Reproduce

Run my sample and swap FlexLayout with StackLayout.

Basic Information

• Version with issue: Xamarin.Forms-pre7

• IDE: Visual Studio for Mac Preview

• Affected Devices: iOS and Android

Reproduction Link

MyApp.zip

[samhouts]

I think this is pretty consistent with our expectations. The CollectionView is meant to expand to its available vertical space. The StackLayout is meant to adjust the height of all items appropriately, so it effectively sets the height of its children. Thanks!

[HobDev]

I think this is pretty consistent with our expectations. The CollectionView is meant to expand to its available vertical space. The StackLayout is meant to adjust the height of all items appropriately, so it effectively sets the height of its children. Thanks!

FlexLayout should also adjust the height of all items appropriately. It is not doing so. The problem is with FlexLayout.

[MeikandaNayanar]

I think this is pretty consistent with our expectations. The CollectionView is meant to expand to its available vertical space. The StackLayout is meant to adjust the height of all items appropriately, so it effectively sets the height of its children. Thanks!

Do we have any documentation stating this?. If so can you please update me the links? I don't see any information as you said in below documentation.
https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/collectionview/

If you still consider this as a behavior, can we add this as a new feature request or an enhancement for some Xamarin controls to achieve this expected behavior (Refer the screenshot for ease)?

[EvoPulseGaming]

CollectionView should only take up the space needed to display the items, if we want to take up the entire screen we would specify this as we do with everything else.

[nwikechisom]

This is still a bug in Xamarin.Forms 4.3 and has not been resolved. I used a StackLayout and Grid in the collection view and gave it a height yet I get a huge space I don't need from the CollectionView. The slider in the image below is supposed to be immediately after the collection View but I have this huge space. This is an urgent need for me. I have to deliver on this project soon.

[BillyMartin1964]

This is extremely silly that you can't center a collectionview when you don't have enough items to fill the screen. Instead of saying it's designed that way... please fix it. How does anyone know ahead of time how may items the user will have. Ridiculous.

[Tuurash]

This seems to be a very effective workaround :)
https://stackoverflow.com/questions/65767461/xamarin-forms-adjusting-height-of-collectionview-to-be-minimum-size-to-fit-chi

[junedmmn]

A recommendation: In short, when displaying a collection that does not expand on the whole screen use StackLayout's BindableLayout. Keep the collection minimal, and optimal, so it will only show a glimpse of the collection. Provide an option to expand this minimal collection that will show whole collection in its original form, display this using CollectionView on another page. But only use CollectionView when you desire to display collection on the whole page/screen.

CollectionView offers virtualization and optimizations on both iOS and Android, hence it does not calculate size of its children and expands to the whole page. Hence use CollectionView when you want to show large collection with complex layout or template. Like list of all records, entries or rows in your app.

Otherwise use StackLayout's BindableLayout to show small minimal collection/list like predictions for search entry, autocomplete, etc.

Hope this helps.