populateMaps method
Populate the maps with the given number of pages.
Implementation
void populateMaps(int numberOfPages) {
_indexedIndexItems.addEntries(List.generate(numberOfPages, (index) => MapEntry(index, {})));
_indexedItemIndexDateTime.addEntries(List.generate(numberOfPages, (index) => MapEntry(index, {})));
_indexedDateTimeItemIndex.addEntries(List.generate(numberOfPages, (index) => MapEntry(index, {})));
_indexedMonthIndices.addEntries(List.generate(numberOfPages, (index) => MapEntry(index, {})));
}