如何在Flutter中保存从DateTimeField中选择的日期时间

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

DateTime selectedDateTime;

DateTimeField(
  format: DateFormat('yyyy-MM-dd HH:mm'), // 设置日期时间格式
  onShowPicker: (context, currentValue) async {
    final date = await showDatePicker(
      context: context,
      initialDate: currentValue ?? DateTime.now(),
      firstDate: DateTime(2000),
      lastDate: DateTime(2100),
    );
    if (date != null) {
      final time = await showTimePicker(
        context: context,
        initialTime: TimeOfDay.fromDateTime(currentValue ?? DateTime.now()),
      );
      selectedDateTime = DateTimeField.combine(date, time);
      return selectedDateTime;
    } else {
      return currentValue;
    }
  },
),

FlatButton(
  onPressed: () {
    if (selectedDateTime != null) {
      // 在这里使用selectedDateTime变量
      print(selectedDateTime);
    } else {
      // 未选择日期时间的处理逻辑
    }
  },
  child: Text('保存'),
),