scroll-to-index not work when use a center key

main.dart

import 'package:flutter/material.dart';
import 'package:scroll_to_index/scroll_to_index.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Scroll To Index Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Scroll To Index Demo'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final scrollDirection = Axis.vertical;

  late AutoScrollController controller;

  late int counter;

  List<int> top = [];
  List<int> bottom = [];

  bool hasCenterKey = true;

  @override
  void initState() {
    super.initState();
    controller = _getController();
    updateTop();

    bottom = List<int>.generate(30, (i) => i);

    counter = top.last;
  }

  void updateTop() {
    if (hasCenterKey) {
      top = List<int>.generate(30, (i) => -(i + 1));
    } else {
      top = List<int>.generate(30, (i) => -(30 - i));
    }
  }

  AutoScrollController _getController() {
    return AutoScrollController(
      axis: scrollDirection,
    );
  }

  void addItems() {
    setState(() {
      top = List<int>.generate(30, (i) => -(30 + 1 - i));
    });
  }

  final Key centerKey = ValueKey('second-sliver-list');

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
        actions: [
          ElevatedButton(
            onPressed: () {
              setState(() {
                hasCenterKey = !hasCenterKey;
                updateTop();
              });
            },
            child: Text('CENTER KEY - ' + (hasCenterKey ? 'ON' : 'OFF')),
          ),
          IconButton(
            onPressed: () async {
              final index = hasCenterKey ? top.last : top.first;
              await controller.scrollToIndex(index);
              controller.highlight(index);
            },
            icon: Text('First'),
          ),
          IconButton(
            onPressed: () async {
              await controller.scrollToIndex(bottom.last);
              controller.highlight(bottom.last);
            },
            icon: Text('Last'),
          ),
        ],
      ),
      body: _buildNestedListView(),
      floatingActionButton: FloatingActionButton(
        onPressed: _nextCounter,
        tooltip: 'Increment',
        child: Text(counter.toString()),
      ),
    );
  }

  Widget _buildNestedListView() {
    return NestedScrollView(
      headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) => [
        SliverOverlapAbsorber(
          handle: NestedScrollView.sliverOverlapAbsorberHandleFor(context),
          sliver: SliverAppBar(),
        )
      ],
      body: CustomScrollView(
        center: hasCenterKey ? centerKey : null,
        scrollDirection: Axis.vertical,
        controller: controller,
        slivers: [
          SliverList(
            delegate: SliverChildBuilderDelegate(
              (BuildContext context, int index) {
                final data = top[index];
                return Padding(
                  padding: EdgeInsets.all(8),
                  child: _getRow(data, data, 50, controller),
                );
              },
              childCount: top.length,
            ),
          ),
          SliverToBoxAdapter(
            child: Container(
              height: 50,
              color: Colors.red,
            ),
          ),
          SliverList(
            key: centerKey,
            delegate: SliverChildBuilderDelegate(
              (BuildContext context, int index) {
                final data = bottom[index];
                return Padding(
                  padding: EdgeInsets.all(8),
                  child: _getRow(data, data, 50, controller),
                );
              },
              childCount: bottom.length,
            ),
          ),
        ],
      ),
    );
  }

  Future _nextCounter() async {
    setState(() {
      if (counter >= bottom.last) {
        counter = top.last;
      } else if ((counter + 10) <= bottom.last) {
        counter = counter + 10;
      } else {
        counter++;
      }
    });
    await _scrollToCounter();
  }

  Future _scrollToCounter() async {
    final result = await controller.scrollToIndex(counter,
        preferPosition: AutoScrollPosition.begin);
    print(result);
    controller.highlight(counter);
  }

  Widget _getRow(
      int index, int value, double height, AutoScrollController controller) {
    return _wrapScrollTag(
        index: index,
        controller: controller,
        child: Container(
          padding: EdgeInsets.all(8),
          alignment: Alignment.topCenter,
          height: height,
          decoration: BoxDecoration(
              border: Border.all(color: Colors.lightBlue, width: 4),
              borderRadius: BorderRadius.circular(12)),
          child: Text('index: $index, height: $height, value: $value'),
        ));
  }

  Widget _wrapScrollTag({
    required int index,
    required Widget child,
    required AutoScrollController controller,
  }) =>
      AutoScrollTag(
        key: ValueKey(index),
        controller: controller,
        index: index,
        child: child,
        highlightColor: Colors.green.withOpacity(0.5),
      );
}