how to change the map

[etcxy]

Hi ,I am a newbie in Flutter and I am in the learning stage. How do I update the map status?

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(
          itemCount: data.length,
          tabBuilder: (BuildContext context, int index, bool active) => Padding(
            padding: EdgeInsets.symmetric(horizontal: 10),
            child: Text(
              data.keys.elementAt(index),
              style: !active
                  ? null
                  : TextStyle(fontWeight: FontWeight.bold, color: Colors.green),
            ),
          ),
          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
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton.extended(
          onPressed: () {
            data.remove('Category A');
          },
          label: Text('delete'),
        ));
  }
}