FIX - The filter applies it to the filtered list instead of to all items in the initial list.

[arakakil]

The filter applies it to the filtered list instead of to all items in the initial list.

The filter method of the FilterState class applies the filter on the items (_items) containing the items that were filtered as you type in the search field.

If a variable is added, e.g. List? _allItems; in which the original list is stored as follows:

FilterState({List<K>? allItems, List<K>? selectedItems}) {
    this.selectedItems = selectedItems;
    items = allItems;
    _allItems = allItems;
  }

And you modify the filter function to use the _allItems variable instead of _items, the problem is solved.

// perform filter operation
  void filter(bool Function(K) filter) {
    _items = _allItems!.where(filter).toList();
    notifyListeners();
  }

You might consider doing a merge of this change?