如何在flutter中显示日期选择器在文本字段的onclick上而不是键盘上？

import 'package:flutter/material.dart';

class DatePickerTextField extends StatefulWidget {
  @override
  _DatePickerTextFieldState createState() => _DatePickerTextFieldState();
}

class _DatePickerTextFieldState extends State<DatePickerTextField> {
  TextEditingController _dateController = TextEditingController();
  DateTime _selectedDate;

  Future<void> _selectDate(BuildContext context) async {
    final DateTime picked = await showDatePicker(
      context: context,
      initialDate: DateTime.now(),
      firstDate: DateTime(2000),
      lastDate: DateTime(2100),
    );
    if (picked != null && picked != _selectedDate) {
      setState(() {
        _selectedDate = picked;
        _dateController.text = picked.toString(); // 将选择的日期显示在文本字段中
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        _selectDate(context); // 点击文本字段时显示日期选择器
      },
      child: TextFormField(
        controller: _dateController,
        decoration: InputDecoration(
          labelText: '选择日期',
        ),
        enabled: false, // 禁用文本字段的键盘输入
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      appBar: AppBar(
        title: Text('DatePicker TextField'),
      ),
      body: Center(
        child: DatePickerTextField(),
      ),
    ),
  ));
}