【Flutter】ピッカー(flutter_picker)を使用し、年月日を選択する方法を解説！

dependencies:
  flutter:
    sdk: flutter
  flutter_picker: ^2.1.0

import 'package:flutter/material.dart';
import 'package:flutter_picker/flutter_picker.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: DatePickerPage(),
    );
  }
}

class DatePickerPage extends StatefulWidget {
  @override
  _DatePickerPageState createState() => _DatePickerPageState();
}

class _DatePickerPageState extends State<DatePickerPage> {
  String _selectedDate = '日付を選択してください';

  void _showPicker() {
    Picker(
      adapter: DateTimePickerAdapter(),
      title: Text('日付を選択'),
      selectedTextStyle: TextStyle(color: Colors.blue),
      onConfirm: (Picker picker, List value) {
        setState(() {
          DateTime selected = (picker.adapter as DateTimePickerAdapter).value!;
          _selectedDate = '${selected.year}年${selected.month}月${selected.day}日';
        });
      }
    ).showDialog(context);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('年月日を選択'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ElevatedButton(
              onPressed: _showPicker,
              child: Text('ピッカーを表示'),
            ),
            Text(_selectedDate),
          ],
        ),
      ),
    );
  }
}