خطا در constructor

من کد زیر را نوشتم ولی زیر public DatePickerFragment خط میکشه وخطای زیر را مینویسه به نظر شما باید چی کار کنم؟

 This fragment should provide a default constructor (a public constructor with no arguments) (de.freewarepoint.whohasmystuff.DatePickerFragment)

Issue: Ensures that Fragment subclasses can be instantiated
Id: ValidFragment

From the Fragment documentation:
Every fragment must have an empty constructor, so it can be instantiated when restoring its activity's state. It is strongly recommended that subclasses do not have other constructors with parameters, since these constructors will not be called when the fragment is re-instantiated; instead, arguments can be supplied by the caller with setArguments(Bundle) and later retrieved by the Fragment with getArguments().

[http://developer.android.com/reference/android/app/Fragment.html#Fragment()]

 public class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {

    final Calendar calendar;

    
	public DatePickerFragment(Calendar calendar) {
        this.calendar = calendar;
   }

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        int year = calendar.get(Calendar.YEAR);
        int month = calendar.get(Calendar.MONTH);
        int day = calendar.get(Calendar.DAY_OF_MONTH);

        return new DatePickerDialog(getActivity(), (AddObject)getActivity(), year, month, day);
    }

    public void onDateSet(DatePicker view, int year, int month, int day) {
        // Do something with the date chosen by the user
    }

}