Wait taking data from one widget to other one appear - flutter

Question

I want the user to pick a date using datePicker widget, when the user finish picking a date, a timePicker widget should appear and do the same thing. After that an item will be added to a list which uses the picked date & time. But what really happens is that everything shows up at the same time.
onPressed: () {
var date = DateTime.now();
showMaterialDatePicker(
context: context,
selectedDate: date,
onChanged: (value) => setState(() => date = value),
);
//Should wait until DatePicker finish
var time = TimeOfDay.now();
showMaterialTimePicker(
context: context,
selectedTime: time,
onChanged: (value) => setState(() => time = value),
);
//Should wait until timePicker finish, to add the item to the list
this.widget.litems.add(Reminder(
time: time,
date: date,
));
setState((){});
}

Answer 1

I suggest using the showDatePicker & showTimePicker. As per the documentation showDatePicker and showTimePicker returns Future. You can simply await these for the desired outcome.
onPressed: () async {
var date = DateTime.now();
date = await showDatePicker(
context: context,
initialDate: date,
);
//Should wait until DatePicker finish
var time = TimeOfDay.now();
time = await showTimePicker(
context: context,
initialTime: time,
);
//Should wait until timePicker finish, to add the item to the list
this.widget.litems.add(Reminder(
time: time,
date: date,
));
setState((){});
}
If you don't want to use these, then you should add showMaterialDatePicker & showMaterialTimePicker to separate functions which returns a Future and handle the logic inside those functions.