Make showDatePicker async

[Stewioie]

Change or add DatePicker.showDatePicker as async like Material showDatePicker

[Macacoazul01]

you can create a date picker in an async function instead of the code and call it in a button press:

void _showDateTimePicker() {

DatePicker.showDatePicker(
  context,
  minuteDivider: 30,
  minDateTime: _startDate1,
  maxDateTime: _endDate1,
  initialDateTime: _startDate1,
  dateFormat: 'dd/MM,HH:mm',
  locale: DateTimePickerLocale.pt_br,
  pickerTheme: DateTimePickerTheme(
    showTitle: true,
  ),
  pickerMode: DateTimePickerMode.datetime, // show TimePicker
  onCancel: () {

  },
  onChange: (dateTime, List<int> index) {
    setState(() {
      _seldata = dateTime;
    });
  },
  onConfirm: (dateTime, List<int> index) {
    setState(() {
      _seldata = dateTime;
    });
  },
);

}