How to clear existing records when page parameter changes?

[arnab]

Context

I have the following RiverPagedBuilder:

@override
Widget build(BuildContext context, WidgetRef ref) =>
    RiverPagedBuilder<Page, Item>(
      firstPageKey: Page(
        key: pageKey,
        orderBy: 'publishedAt',
        descending: true,
      ),
      limit: 50,
      provider: paginatedControllerProvider,
      itemBuilder: (context, item, index) => ItemListTile(
        item,
      ),
      pagedBuilder: (controller, builder) => PagedSliverList.separated(
        pagingController: controller,
        builderDelegate: builder,
        separatorBuilder: (ctx, i) => const Divider(
          thickness: 0.8,
          height: 2,
        ),
      ),
    );

And here is the paginatedControllerProvider:

part 'paginated_controller.freezed.dart';

class PaginatedController extends PagedNotifier<Page, Item> {
  final ItemRepository _repository;
  final Logger logger;

  PaginatedController(this._repository, this.logger)
      : super(
          load: (page, limit) {
            logger.i('Fetching next $limit of $page');
            return _repository
                .listItems(
                  itemId: page.itemId,
                  orderBy: page.orderBy,
                  descending: page.descending,
                  lastItem: page.lastItem,
                  limit: limit,
                )
                .first;
          },
          nextPageKeyBuilder: (List<Item>? lastItems, Page page, int limit) =>
              (lastItems == null || lastItems.length < limit)
                  ? null
                  : Page(
                      itemId: page.itemId,
                      orderBy: page.orderBy,
                      descending: page.descending,
                      lastItem: lastItems.last.publishedAt,
                    ),
        );
}

final paginatedControllerProvider = StateNotifierProvider<
    PaginatedController,
    PagedState<Page, Item>>(
  (ref) => PaginatedController(
    ref.read(itemRepositoryProvider),
    ref.read(loggerProvider),
  ),
);

@freezed
class Page with _$Page {
  const Page._();

  const factory Page({
    required String itemId,
    required String orderBy,
    required bool descending,
    @Default(null) dynamic lastItem,
  }) = _Page;
}

Problem

This works great as long as the itemId does not change. When I navigate to a page the first time, it pulls in the expected lastest items (descending order by publishedAt). And then after that, on scrolling it loads the older items, again as expected.

However, when I navigate to a different item page (i.e. itemId is different), it adds the records for this new item to the existing state of records.

I would like to clear the state when the itemId changes. How can I achieve this (or am I not fundamentally using it in a different way)?

[arnab]

For now, I am detecting in GoRouter's redirect hook if the app is redirecting to the screen in question, and clearing the state of paginated items, if so.

But it does sound like a hack. Please let me know if there is a better way.

[ftognetto]

Hi @arnab sorry I've not been using flutter for a long time, are you still interested in a help here?
From what I see maybe a family provider is needed in your case where the family is the itemId