Can't access DatePicker.ValidationCallback in my code
问题 I have a simple DatePickerFragment that extends DialogFragment. I'm wanting to set a validation callback so I can prevent "OK" being selected if an invalid date is picked. I first tried setMaxDate and that grays out the invalid choices but still allows them to be selected and OK to be pressed. So I was hoping setting the validation callback would be the solution. abstract public class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener { public