code: private void updateDisplay(boolean allowEmptyDisplay) {
          if (!allowEmptyDisplay && mTypedTimes.isEmpty()) {
              int hour = mTimePicker.getHours();
              int minute = mTimePicker.getMinutes();
              setHour(hour, true);
              setMinute(minute);
              if (!mIs24HourMode) {
                  updateAmPmDisplay(hour < 12 ? AM : PM);
              }
              setCurrentItemShowing(mTimePicker.getCurrentItemShowing(), true, true, true);
              mDoneButton.setEnabled(true);
          } else {
              Boolean[] enteredZeros = {false, false};
              int[] values = getEnteredTime(enteredZeros);
              String hourFormat = enteredZeros[0] ? "%02d" : "%2d";
              String minuteFormat = (enteredZeros[1]) ? "%02d" : "%2d";
              String hourStr = (values[0] == -1) ? mDoublePlaceholderText :
                      String.format(hourFormat, values[0]).replace(' ', mPlaceholderText);
              String minuteStr = (values[1] == -1) ? mDoublePlaceholderText :
                      String.format(minuteFormat, values[1]).replace(' ', mPlaceholderText);
              mHourView.setText(hourStr);
              mHourSpaceView.setText(hourStr);
              mHourView.setSelected(false);
              mMinuteView.setText(minuteStr);
              mMinuteSpaceView.setText(minuteStr);
              mMinuteView.setSelected(false);
              if (!mIs24HourMode) {
                  updateAmPmDisplay(values[2]);
              }
          }
      }
docs: Update the hours, minutes, and AM/PM displays with the typed times. If the typedTimes is
  empty, either show an empty display (filled with the placeholder text), or update from the
  timepicker's values.
  
  @param allowEmptyDisplay if true, then if the typedTimes is empty, use the placeholder text.
  Otherwise, revert to the timepicker's values.