flutter/examples/api/lib/material/snack_bar/snack_bar.2.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 [SnackBar] with Material 3 specifications.

import 'package:flutter/material.dart';

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

// A Material 3 [SnackBar] demonstrating an optional icon, in either floating
// or fixed format.
class MyApp extends StatelessWidget {
  const MyApp({super.key});

  static const String _title = 'Flutter Code Sample';

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

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

  @override
  State<SnackBarExample> createState() => _SnackBarExampleState();
}

class _SnackBarExampleState extends State<SnackBarExample> {
  SnackBarBehavior? _snackBarBehavior = SnackBarBehavior.floating;
  bool _withIcon = true;
  bool _withAction = true;
  bool _multiLine = false;
  bool _longActionLabel = false;

  Padding _configRow(List<Widget> children) => Padding(
      padding: const EdgeInsets.all(8.0), child: Row(children: children));

  @override
  Widget build(BuildContext context) {
    return Padding(padding: const EdgeInsets.only(left: 50.0), child: Column(
      children: <Widget>[
        _configRow(<Widget>[
          Text('Snack Bar configuration',
              style: Theme.of(context).textTheme.bodyLarge),
        ]),
        _configRow(
          <Widget>[
            const Text('Fixed'),
            Radio<SnackBarBehavior>(
              value: SnackBarBehavior.fixed,
              groupValue: _snackBarBehavior,
              onChanged: (SnackBarBehavior? value) {
                setState(() {
                  _snackBarBehavior = value;
                });
              },
            ),
            const Text('Floating'),
            Radio<SnackBarBehavior>(
              value: SnackBarBehavior.floating,
              groupValue: _snackBarBehavior,
              onChanged: (SnackBarBehavior? value) {
                setState(() {
                  _snackBarBehavior = value;
                });
              },
            ),
          ],
        ),
        _configRow(
          <Widget>[
            const Text('Include Icon '),
            Switch(
              value: _withIcon,
              onChanged: (bool value) {
                setState(() {
                  _withIcon = !_withIcon;
                });
              },
            ),
          ],
        ),
        _configRow(
          <Widget>[
            const Text('Include Action '),
            Switch(
              value: _withAction,
              onChanged: (bool value) {
                setState(() {
                  _withAction = !_withAction;
                });
              },
            ),
            const SizedBox(width: 16.0),
            const Text('Long Action Label '),
            Switch(
              value: _longActionLabel,
              onChanged: !_withAction
                  ? null
                  : (bool value) {
                      setState(() {
                        _longActionLabel = !_longActionLabel;
                      });
                    },
            ),
          ],
        ),
        _configRow(
          <Widget>[
            const Text('Multi Line Text'),
            Switch(
              value: _multiLine,
              onChanged: _snackBarBehavior == SnackBarBehavior.fixed ? null : (bool value) {
                setState(() {
                  _multiLine = !_multiLine;
                });
              },
            ),
          ],
        ),
        const SizedBox(height: 16.0),
        ElevatedButton(
          child: const Text('Show Snackbar'),
          onPressed: () {
            ScaffoldMessenger.of(context).showSnackBar(_snackBar());
          }
        ),
      ],
    ),
  );
}

  SnackBar _snackBar() {
    final SnackBarAction? action = _withAction
        ? SnackBarAction(
            label: _longActionLabel ? 'Long Action Text' : 'Action',
            onPressed: () {
              // Code to execute.
            },
          )
        : null;
    final double? width =
        _snackBarBehavior == SnackBarBehavior.floating && _multiLine ? 400.0 : null;
    final String label = _multiLine
        ? 'A Snack Bar with quite a lot of text which spans across multiple lines'
        : 'Single Line Snack Bar';
    return SnackBar(
      content: Text(label),
      showCloseIcon: _withIcon,
      width: width,
      behavior: _snackBarBehavior,
      action: action,
      duration: const Duration(seconds: 3),
    );
  }
}