如何在TextFormField中显示输入时间？

dependencies:
  flutter:
    sdk: flutter
  intl: ^0.17.0

DateTime selectedTime;

TextEditingController _timeController = TextEditingController();

onTap: () {
  showTimePicker(
    context: context,
    initialTime: TimeOfDay.now(),
  ).then((selected) {
    if (selected != null) {
      setState(() {
        selectedTime = DateTime(
          DateTime.now().year,
          DateTime.now().month,
          DateTime.now().day,
          selected.hour,
          selected.minute,
        );
        _timeController.text = DateFormat.Hm().format(selectedTime);
      });
    }
  });
},

initialValue: selectedTime != null ? DateFormat.Hm().format(selectedTime) : null,