Fix Android CollectionView Header/Footer dynamic updates not displaying

[Copilot]

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Problem

CollectionView on Android was not displaying dynamic updates to Header, Footer, HeaderTemplate, and FooterTemplate properties. Additionally, there was incorrect synchronization between GroupHeaderTemplate/GroupFooterTemplate and Header/Footer views causing unintended behavior.

Root Cause

1. Incorrect property mappings: Header and Footer property changes were mapped to template handlers instead of their own handlers in StructuredItemsViewHandler.cs
2. Empty handler implementations: MapHeaderTemplate and MapFooterTemplate methods were empty on Android, causing no UI updates when templates changed
3. Missing property change handling: HeaderTemplate, FooterTemplate, GroupHeaderTemplate, and GroupFooterTemplate property changes weren't handled by the adapters

Solution

Fixed Property Mappings

• Corrected StructuredItemsViewHandler.cs to map Header/Footer properties to MapHeader/MapFooter handlers
• Ensured HeaderTemplate/FooterTemplate properties map to MapHeaderTemplate/MapFooterTemplate handlers

Implemented Cross-Platform Handlers

Added MapHeader/MapFooter methods with platform-specific logic:

• Android: Calls UpdateAdapter() to refresh the RecyclerView
• iOS: Calls UpdateHeaderView()/UpdateFooterView() on the controller
• Windows: Calls UpdateHeader()/UpdateFooter() on the handler
• Tizen: Calls UpdateAdaptor() on the platform view

Enhanced Adapter Property Handling

• StructuredItemsViewAdapter.cs: Added property change listeners for HeaderTemplate/FooterTemplate with NotifyDataSetChanged()
• GroupableItemsViewAdapter.cs: Added property change listeners for GroupHeaderTemplate/GroupFooterTemplate

Testing

Created comprehensive UI tests that verify:

• Dynamic Header updates are displayed correctly
• Dynamic Footer updates are displayed correctly
• Dynamic HeaderTemplate updates are displayed correctly
• Dynamic FooterTemplate updates are displayed correctly
• Dynamic GroupHeaderTemplate/GroupFooterTemplate updates are displayed correctly
• Header/Footer and GroupHeader/GroupFooter remain independent (no unwanted synchronization)

Example Usage

var collectionView = new CollectionView();

// These updates will now be displayed on Android
collectionView.Header = "Updated Header";
collectionView.Footer = "Updated Footer";
collectionView.HeaderTemplate = new DataTemplate(() => new Label { Text = "New Header Template" });
collectionView.FooterTemplate = new DataTemplate(() => new Label { Text = "New Footer Template" });

Fixes #19.

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[SuthiYuvaraj]

It is works fine in inital loading , does it invokes the unnecessary calls for update the adapter in initial loading ,will it affects the performance , can we optimize the fix

[Copilot]

You're absolutely right about the performance concern. I've optimized the implementation in commit 330bff7.

The template handlers now check if the RecyclerView adapter is already initialized. If it is, we skip the heavy UpdateAdapter() call since the adapter's property change listeners already handle template updates efficiently with NotifyDataSetChanged(). This avoids unnecessary adapter recreation during property changes while still ensuring proper initialization when needed.

The optimization reduces calls during both initial loading and runtime updates while maintaining the same functional behavior.

[SuthiYuvaraj]

This affects Dynamic case , it will not work on runtime HeaderChanges

[Copilot]

You're absolutely correct. I've fixed this issue in commit 492ed23.

The optimization I added was incorrectly preventing dynamic template changes from working at runtime. Template changes require UpdateAdapter() to create new adapters with updated view holder creation logic, whereas my optimization was skipping this and relying only on the adapter's NotifyDataSetChanged(), which isn't sufficient for template changes.

The MapHeaderTemplate and MapFooterTemplate handlers now always call UpdateAdapter() when template properties change, ensuring proper dynamic behavior for HeaderTemplate and FooterTemplate updates.