MonthPicker({Key key, @required DateTime selectedDate, @required ValueChanged<DateTime> onChanged, @required DateTime firstDate, @required DateTime lastDate })

Creates a month picker.

Rarely used directly. Instead, typically used as part of a DatePicker.

Source 

MonthPicker({
  Key key,
  @required this.selectedDate,
  @required this.onChanged,
  @required this.firstDate,
  @required this.lastDate
}) : super(key: key) {
  assert(selectedDate != null);
  assert(onChanged != null);
  assert(lastDate.isAfter(firstDate));
  assert(selectedDate.isAfter(firstDate) || selectedDate.isAtSameMomentAs(firstDate));
}