dependencies:
 scrollable_list_tab_scroller: <latest>

import 'package:flutter/material.dart';
import 'package:scrollable_list_tab_scroller/scrollable_list_tab_scroller.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: 'Scrollable List Tab Scroller',
   theme: ThemeData(
     primarySwatch: Colors.blue,
   ),
   home: MyHomePage(title: 'Scrollable List Tab Scroller'),
 );
}
}

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 data = {
 "Category A": [
   "Item 1 (A)",
   "Item 2 (A)",
   "Item 3 (A)",
   "Item 4 (A)",
 ],
 "Category B": [
   "Item 1 (B)",
   "Item 2 (B)",
 ],
 "Category C": [
   "Item 1 (C)",
   "Item 2 (C)",
   "Item 3 (C)",
   "Item 4 (C)",
   "Item 5 (C)",
 ],
 "Category D": [
   "Item 1 (D)",
   "Item 2 (D)",
   "Item 3 (D)",
   "Item 4 (D)",
   "Item 5 (D)",
   "Item 6 (D)",
   "Item 7 (D)",
   "Item 8 (D)",
   "Item 9 (D)",
 ],
};

@override
Widget build(BuildContext context) {
 return Scaffold(
     appBar: AppBar(
       title: Text(widget.title),
     ),
     body: ScrollableListTabScroller(
       tabBuilder: (BuildContext context, int index, bool active) => Text(
         data.keys.elementAt(index),
         style: !active
             ? null
             : TextStyle(fontWeight: FontWeight.bold, color: Colors.green),
       ),
       itemCount: data.length,
       itemBuilder: (BuildContext context, int index) => Column(
         children: [
           Text(
             data.keys.elementAt(index),
             style: TextStyle(fontWeight: FontWeight.bold, fontSize: 20),
           ),
           ...data.values
               .elementAt(index)
               .asMap()
               .map(
                 (index, value) => MapEntry(
                   index,
                   ListTile(
                     leading: Container(
                       height: 40,
                       width: 40,
                       decoration: BoxDecoration(
                           shape: BoxShape.circle, color: Colors.grey),
                       alignment: Alignment.center,
                       child: Text(index.toString()),
                     ),
                     title: Text(value),
                   ),
                 ),
               )
               .values
         ],
       ),
     ));
}
}