【StatelessWidget】Flutterでボタンを表示する方法

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Stateless Button Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const ButtonDemoPage(),
    );
  }
}

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

  void _showSnackBar(BuildContext context, String buttonName) {
    ScaffoldMessenger.of(context).hideCurrentSnackBar();
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(
        content: Text('$buttonName がタップされました！'),
        duration: const Duration(seconds: 1),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('StatelessWidget ボタン一覧'),
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
      ),
      body: Center(
        child: SingleChildScrollView(
          padding: const EdgeInsets.all(16.0),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              // 1. ElevatedButton（主要アクション）
              ElevatedButton(
                onPressed: () => _showSnackBar(context, 'ElevatedButton'),
                child: const Text('ElevatedButton'),
              ),
              const SizedBox(height: 12),

              // 2. FilledButton（強調表示）
              FilledButton(
                onPressed: () => _showSnackBar(context, 'FilledButton'),
                child: const Text('FilledButton'),
              ),
              const SizedBox(height: 12),

              // 3. OutlinedButton（枠線あり）
              OutlinedButton(
                onPressed: () => _showSnackBar(context, 'OutlinedButton'),
                child: const Text('OutlinedButton'),
              ),
              const SizedBox(height: 12),

              // 4. TextButton（テキストのみ）
              TextButton(
                onPressed: () => _showSnackBar(context, 'TextButton'),
                child: const Text('TextButton'),
              ),
              const SizedBox(height: 12),

              // 5. アイコン付きボタン
              ElevatedButton.icon(
                onPressed: () => _showSnackBar(context, 'アイコン付きボタン'),
                icon: const Icon(Icons.send),
                label: const Text('送信する'),
              ),
              const SizedBox(height: 12),

              // 6. 全幅カスタムボタン
              SizedBox(
                width: double.infinity,
                child: ElevatedButton(
                  onPressed: () => _showSnackBar(context, 'カスタムボタン'),
                  style: ElevatedButton.styleFrom(
                    backgroundColor: Colors.teal,
                    foregroundColor: Colors.white,
                    padding: const EdgeInsets.symmetric(vertical: 16),
                    shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.circular(12),
                    ),
                  ),
                  child: const Text(
                    '全幅カスタムボタン',
                    style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
                  ),
                ),
              ),
              const SizedBox(height: 12),

              // 7. 無効化（Disabled）ボタン
              const ElevatedButton(
                onPressed: null,
                child: Text('無効化ボタン'),
              ),
            ],
          ),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => _showSnackBar(context, 'FloatingActionButton'),
        child: const Icon(Icons.add),
      ),
    );
  }
}