選択の状態を制御するために使われるボタンです。
import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final List<bool> isSelected = [false, false, false];
  @override
  Widget build(BuildContext context) {
    return ToggleButtons(
      children: const <Widget>[
        Icon(Icons.ac_unit),
        Icon(Icons.call),
        Icon(Icons.cake),
      ],
      onPressed: (int index) {
        setState(() {
          isSelected[index] = !isSelected[index];
        });
      },
      isSelected: isSelected,
    );
  }
}