你可以在showDialog上使用CalendarDatePicker小部件。它提供了onDateChanged可以用来关闭对话框并传递selectedDate。

_datePicker() async {
    _myDateTime = await showDialog(
      context: context,
      builder: (context) {
        return LayoutBuilder(builder: (_, constraints) {
          final width = constraints.maxWidth;
          final height = constraints.maxHeight;

          return Center(
            child: Material(
              // ok or cancel buttons arent needed for this case, else you can use AlertDialog for general purpose
              child: SizedBox(
                width: width * 0.8, // cant managed being expanded
                child: CalendarDatePicker(
                  initialDate: DateTime.now(),
                  firstDate: DateTime.now(),
                  lastDate: DateTime(2100),
                  onDateChanged: (DateTime value) {
                    Navigator.of(context).pop(value);
                  },
                ),
              ),
            ),
          );
        });
      },
    );

    debugPrint("selected date is $_myDateTime");
  }