[Android] Fix incorrect spacing in CollectionView with multiple spans

[ChummerUA]

Description of Change

Fixed incorrect spacing in CollectionView with multiple spans

Issues Resolved

• fixes [Bug] [Android] Collection View wrong first/last item sizing (on Orientation=Vertical and Span > 1) #9125
• fixes [Bug] CollectionView GridLayout items spacing #10585
• fixes [Bug] CollectionView on Android does not layout new items properly #13054
• fixes CollectionView LinearItemsLayout strange behavior on Android[Bug] [CollectionView] [Android] #9681

API Changes

None

Platforms Affected

• Android

Behavioral/Visual Changes

CollectionView doesn't add additional space to some items when layout have multiple spans anymore. Spacing now also updates correctly when ObservableCollection ItemsSource is updated.

Before/After Screenshots

Before

After

PR Checklist

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

[dnfclas]

All CLA requirements met.

[domagojmedo]

Why is item: 5 higher than other items in first image? Same thing with item: 4 in third image

[ChummerUA]

@domagojmedo they have incorrect sizes because ItemDecoration in native renderer configured incorrectly. Also adapter need extra notifications when ItemsSource is updated in order to update ItemDecoration correctly

[domagojmedo]

@ChummerUA do you know if there is an issue for that already?

[ChummerUA]

@domagojmedo I linked issues that I found into description. There's your issue and another one

[hartez]

@ChummerUA @PureWeen The API 19 test failures are happening because of a weird thing with the CarouselView's custom adapter; it does some weird things with ItemCount, so the NotifyItemRangeChanged calls are grinding to a halt. I'm looking into it.

[hartez]

Anyway, I think I need to check my solution because I noticed one issue. Spacing is calculated correctly but items on the edges have incorrect size. For example, items in first and last columns of vertical grid with 3 and more than spans will have different width than ones in inner columns

@ChummerUA @PureWeen I think I see why this is happening - the GetItemOffsets method is using GetChildAdapterPosition(view) to determine an index for the item. But the index also depends on whether there are header/footer items, so with a header in place the index is off by one and the offsets for the items on the edges are calculated wrong.

I think I see how we can fix this; the SpacingItemDecoration will need to have the SpanSizeLookup item passed in from the ItemsViewRenderer; the SpanSizeLookup. I'll implement that in the morning and see if we can fix this issue.

[ChummerUA]

@hartez
It is happening because inner items being clipped equally from all sides in order to achieve correct spacing, while edge items are clipped only on the inner sides. In order to achieve both same sizes and correct spacing, horizontal offsets for each column in vertical collection/vertical offsets for each row in horizontal collection must have different values

[rmarinho]

@hartez the tests on Android are taking more than 6H .. i m trying to figure if it's related with changes or not, but since it happens on all android environments i have a feeling is related with the changes.

[hartez]

@rmarinho I ran them locally on a device and they finished in 4 hours, so I don't think it's these changes causing the problem.

[rmarinho]

@hartez they keep failing on CI..

[Cr15Denis]

similar problem #13044

[mhrastegari]

we still have problem with this! when we update span count or device orientation the items size(Height) won't update correctly in Griditemlayout