code: void selectDay(int year, int month, int day) {
          Calendar cal = Calendar.getInstance();
          cal.set(year, month, day);
          Date date = cal.getTime();
          this.field.setText(simpleDateFormat.format(date));
          if (popup != null) {
              popup.hide();
              popup = null;
          }
      }
docs: Set date to text field
  
  @param year
  year to set
  @param month
  month to set
  @param day
  day to set