在flutter应用中添加日期选择器的正确方法是什么？

在Flutter应用中添加日期选择器，你可以使用showDatePicker函数。这个函数会弹出一个日期选择对话框，用户可以在其中选择日期。以下是一个简单的示例：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Date Picker Example')),
        body: Center(child: DatePickerButton()),
      ),
    );
  }
}

class DatePickerButton extends StatefulWidget {
  @override
  _DatePickerButtonState createState() => _DatePickerButtonState();
}

class _DatePickerButtonState extends State<DatePickerButton> {
  DateTime selectedDate = DateTime.now();

  Future<void> _selectDate(BuildContext context) async {
    final DateTime? picked = await showDatePicker(
      context: context,
      initialDate: selectedDate,
      firstDate: DateTime(2015, 8),
      lastDate: DateTime(2101),
    );
    if (picked != null && picked != selectedDate) {
      setState(() {
        selectedDate = picked;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: () => _selectDate(context),
      child: Text('Select date: ${selectedDate.year}-${selectedDate.month}-${selectedDate.day}'),
    );
  }
}