下面的代码将texteditingcontroller中名为_date的文本解析为datetime格式，并将其用作选择器的初始日期。如果控制器的文本为空，则使用DateTime.now()

onTap: () async {
          DateTime? pickeddate = await showDatePicker(
              context: context,
              initialDate: _date.text.isEmpty ? DateTime.now() : DateTime.parse(_date.text),
              firstDate: DateTime(2000),
              lastDate: DateTime(2101));

          if (pickeddate != null) {
            setState(() {
              _date.text = DateFormat('yyyy-MM-dd').format(pickeddate);
              currentDateSelected = _date.text;
              // updateDate(DateFormat('yyyy-MM-dd').format(pickeddate));
              _refreshSets();
              //print(DateFormat('yyyy-MM-dd').format(pickeddate));
            });
          }

          //Here i need to send off to the database that pickeddate
        }

读取the doc中的showDatePicker构造函数

Future<DateTime?> showDatePicker(
{required BuildContext context,
required DateTime initialDate,
required DateTime firstDate,
required DateTime lastDate,
DateTime? currentDate,
...

currentDate表示当前日期（即今天）。此日期将在日网格中突出显示。如果为空，则DateTime.now将使用www.example.com（）的日期。这导致了你的问题。

您有一个名为initialDate的属性，用于设置日期选择器的初始值。

DateTime selectedDate = DateTime.now();
...
 onTap: () async {
     DateTime? pickedDate = await showDatePicker(
        context: context,
        initialDate: selectedDate,
        firstDate: DateTime(2000),
        lastDate: DateTime(2101)
     );

     if (pickedDate != null) {
      setState(() {
        selectedDate = pickedDate;
        // Update selectedDate, so that now the new selected date acts
        // as the initial selected value
       });
     }
...

确保使用StatefulWidget并声明selectedDate变量，如下所示：

class _MyWidgetState extends State<MyWidget> {
   DateTime selectedDate = DateTime.now();
 ...
}