Invalidate CollectionView Layout on transition to IsVisible = true

[hartez]

Description of Change

If the CollectionView is the root Content element for a page on iOS and IsVisible transitions from false to true, the CollectionView's layout is not invalidating. This change invalidates the layout so that the CollectionView is refreshed.

Note that this isn't an issue if the CollectionView is inside some other view (e.g., a StackLayout); it's only an issue if it's the root of the page Content.

Issues Resolved

• fixes [Bug] [iOS] CollectionView does not bind to items if IsVisible=False #13203

API Changes

None

Platforms Affected

• iOS

Behavioral/Visual Changes

None

Before/After Screenshots

Not applicable

Testing Procedure

Automated UI test

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)

[rmarinho]

Are you missing a button with "RunTest" @hartez ?

[hartez]

Are you missing a button with "RunTest" @hartez ?

Yep, I forgot I changed the test to use Appearing. :(

[AlleSchonWeg]

Note that this isn't an issue if the CollectionView is inside some other view (e.g., a StackLayout); it's only an issue if it's the root of the page Content.

I have the same issue, but my CollectionView is inside some other view.

[hartez]

Note that this isn't an issue if the CollectionView is inside some other view (e.g., a StackLayout); it's only an issue if it's the root of the page Content.

I have the same issue, but my CollectionView is inside some other view.

@AlleSchonWeg I should clarify - it's not an issue if the container view is one that will be invalidated if one of its children changes its size or visibility. StackLayout, Grid, FlexLayout, etc. all recompute their layouts if a child control's visibility changes. There may be other containers which do not. I just included that note for folks who need an immediate workaround; wrapping the CollectionView in a StackLayout or Grid will fix the issue temporarily while waiting for the next release.

It's all moot after this change is merged, because the CollectionView itself will invalidate its own layout after a visibility change. So it shouldn't matter what type the container is.

[hartez]

Does this need to be unregistered? Wouldn't want a new memory leak.

It'd be unusual, but I suppose a situation where the user is holding on to ItemsView and reusing it in another renderer could leak the controller. Added the unsubscribe during Dispose.

[rachelkang]

Are these failing tests relevant?

[PureWeen]

@rachelkang those failures are not relevant