flutter/examples/api/lib/material/checkbox/checkbox.1.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Flutter code sample for M3 Checkbox with error state

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(useMaterial3: true, colorSchemeSeed: const Color(0xff6750a4)),
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: const Center(
          child: MyStatefulWidget(),
        ),
      ),
    );
  }
}

class MyStatefulWidget extends StatefulWidget {
  const MyStatefulWidget({super.key});

  @override
  State<MyStatefulWidget> createState() => _MyStatefulWidgetState();
}

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  bool? isChecked = true;

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        Checkbox(
          tristate: true,
          value: isChecked,
          onChanged: (bool? value) {
            setState(() {
              isChecked = value;
            });
          },
        ),
        Checkbox(
          isError: true,
          tristate: true,
          value: isChecked,
          onChanged: (bool? value) {
            setState(() {
              isChecked = value;
            });
          },
        ),
        Checkbox(
          isError: true,
          tristate: true,
          value: isChecked,
          onChanged: null,
        ),
      ],
    );
  }
}