Added

• PagingListener widget to connect a PagingController to a PagedLayoutBuilder.

Changed

• PagingController no longer has addPageRequestListener method and firstPageKey parameter. Use the fetchPage parameter of the constructor instead.
• PagingController no longer has the itemList, error, and nextPageKey getters and setters. All values are now stored in PagingState.
• PagingController no longer has the appendPage and appendLastPage methods. Use the copyWith method of PagingState to update its pages, keys, and hasNextPage fields.
• PagingController no longer has the retryLastFailedRequest method. You can simply call fetchNextPage to try again.
• PagingController no longer has the invisibleItemsThreshold field. It is now configured in PagedChildBuilderDelegate.
• PagingController now features getters matching the fields of PagingState as well as mapItems to modify the items.
• PagedLayoutBuilder no longer accepts pagingController as a parameter. It now takes PagingState and fetchNextPage instead.
• PagingState now uses pages (List<List<ItemType>>) instead of itemList (List<ItemType>). A new extension getter items is provided for flattening.
• PagingState now features keys, a list storing all fetched keys, and hasNextPage replacing nextPageKey.
• PagingState now includes isLoading, which tracks whether a request is in progress.
• PagingState now provides error as type Object? instead of dynamic.
• PagingState now includes mapItems and filterItems extension methods for modifying items conveniently.

Fixed

• PagingController now deduplicates requests.
• PagingController refresh operations now cancel previous requests.
• Off-by-one error in invisibleItemsThreshold calculation.
• Failure to trigger page request when invisibleItemsThreshold is too large.
• Animating between states with animateTransitions.