Mulitple levels

[tas-unn]

I have a file with this structure: https://jsoneditoronline.org/#left=cloud.5c3ee044771a4f25ab22407409e0da1b (number of items in "listlevel1" may vary and reach up to 2000) How can I make sure that my list loads correctly as I go down? I have now done that it is loaded by 20 elements, but the whole list at once

`

class _State extends State<ShownSp> {
static const _pageSize = 20;
bool islast = false;
PagingController<int, Abit> _pagingController =
	PagingController(firstPageKey: 0);
List<Abit> abs = List.empty();

@override
void initState() {
	_pagingController.addPageRequestListener((pageKey) {
	_fetchPage(pageKey);
	});
	super.initState();

}

void dispose() {
	_pagingController.dispose();
	super.dispose();
}

Future<void> _fetchPage(int pageKey) async {

try {
  final List<Abit> newItems = List.empty(growable: true);

  if (abs.length != 0) {
    int min = 0;
    if (_pageSize < abs.length - pageKey * _pageSize)
      min = _pageSize;
    else
      min = abs.length - pageKey * _pageSize;

    for (var i = 0; i < min; i++) {

      newItems.add(abs[pageKey * _pageSize + i]);
    }
    islast = true;
  }
  final isLastPage = newItems.length < _pageSize;
  if (isLastPage && islast) {

    _pagingController.appendLastPage(newItems);
  } else {
    final nextPageKey = pageKey + 1;

    _pagingController.appendPage(newItems, nextPageKey);
  }
} catch (error) {
  _pagingController.error = error;
  print(error);
}
}

........


ListView.builder(
                    physics: NeverScrollableScrollPhysics(),
                    shrinkWrap: true,
                    itemCount: mydata.dinlist.length,
                    itemBuilder: (BuildContext context, int index) {
                      abs = mydata.dinlist[index].abit;

                      islast = false;
                      _pagingController = PagingController(firstPageKey: 0);
                      _pagingController.addPageRequestListener((pageKey) {
                        _fetchPage(pageKey);
                      });
                      return Column(
                        children: [
                          Container(
                            color: Color.fromRGBO(216, 249, 170, 1),
                            child: ListTile(
                              title: Text(
                                  mydata.dinlist[index].name + txtkolmest),
                            ),
                          ),
                          PagedListView<int, dynamic>(
                            physics: NeverScrollableScrollPhysics(),
                            shrinkWrap: true,
                            pagingController: _pagingController,
                            builderDelegate:
                                PagedChildBuilderDelegate<dynamic>(
                                    itemBuilder: (BuildContext context1,
                                        item, int index1) {
                              Abit a = item;
                              islast=true;
return (Text(a.fio))

}}}}

`