src/com/squareup/timessquare/CalendarPickerView.java

// Copyright 2012 Square, Inc.
package com.squareup.timessquare;
import static java.util.Calendar.DATE;
import static java.util.Calendar.DAY_OF_MONTH;
import static java.util.Calendar.DAY_OF_WEEK;
import static java.util.Calendar.HOUR_OF_DAY;
import static java.util.Calendar.MILLISECOND;
import static java.util.Calendar.MINUTE;
import static java.util.Calendar.MONTH;
import static java.util.Calendar.SECOND;
import static java.util.Calendar.YEAR;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import java.util.Locale;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.Toast;
import com.ectrip.trips.check.R;
import com.squareup.timessquare.MonthCellDescriptor.RangeState;
/**
 * Android component to allow picking a date from a calendar view (a list of
 * months). Must be initialized after inflation with {@link #init(Date, Date)}
 * and can be customized with any of the {@link FluentInitializer} methods
 * returned. The currently selected date can be retrieved with
 * {@link #getSelectedDate()}.
 */
public class CalendarPickerView extends ListView {
	public enum SelectionMode {
		/**
		 * Only one date will be selectable. If there is already a selected date
		 * and you select a new one, the old date will be unselected.
		 */
		SINGLE,
		/**
		 * Multiple dates will be selectable. Selecting an already-selected date
		 * will un-select it.
		 */
		MULTIPLE,
		/**
		 * Allows you to select a date range. Previous selections are cleared
		 * when you either:
		 * <ul>
		 * <li>Have a range selected and select another date (even if it's in
		 * the current range).</li>
		 * <li>Have one date selected and then select an earlier date.</li>
		 * </ul>
		 */
		RANGE
	}
	private final CalendarPickerView.MonthAdapter adapter;
	private final List<List<List<MonthCellDescriptor>>> cells = new ArrayList<List<List<MonthCellDescriptor>>>();
	final MonthView.Listener listener = new CellClickedListener();
	final List<MonthDescriptor> months = new ArrayList<MonthDescriptor>();
	final List<MonthCellDescriptor> selectedCells = new ArrayList<MonthCellDescriptor>();
	final List<MonthCellDescriptor> highlightedCells = new ArrayList<MonthCellDescriptor>();
	final List<Calendar> selectedCals = new ArrayList<Calendar>();
	final List<Calendar> highlightedCals = new ArrayList<Calendar>();
	private Locale locale;
	private DateFormat monthNameFormat;
	private DateFormat weekdayNameFormat;
	private DateFormat fullDateFormat;
	private Calendar minCal;
	private Calendar maxCal;
	private Calendar monthCounter;
	private boolean displayOnly;
	SelectionMode selectionMode;
	Calendar today;
	private int dividerColor;
	private int dayBackgroundResId;
	private int dayTextColorResId;
	private int titleTextColor;
	private int headerTextColor;
	private OnDateSelectedListener dateListener;
	private DateSelectableFilter dateConfiguredListener;
	private OnInvalidDateSelectedListener invalidDateListener = new DefaultOnInvalidDateSelectedListener();
	public CalendarPickerView(Context context, AttributeSet attrs) {
		super(context, attrs);
		Resources res = context.getResources();
		TypedArray a = context.obtainStyledAttributes(attrs,
				R.styleable.CalendarPickerView);
		final int bg = a.getColor(
				R.styleable.CalendarPickerView_android_background,
				res.getColor(R.color.calendar_bg));
		dividerColor = a.getColor(R.styleable.CalendarPickerView_dividerColor,
				res.getColor(R.color.calendar_divider));
		dayBackgroundResId = a.getResourceId(
				R.styleable.CalendarPickerView_dayBackground,
				R.drawable.mr_calendar_bg_selector);
		dayTextColorResId = a.getResourceId(
				R.styleable.CalendarPickerView_dayTextColor,
				R.color.mr_calendar_text_selector);
		titleTextColor = a.getColor(
				R.styleable.CalendarPickerView_titleTextColor,
				R.color.calendar_text_active);
		headerTextColor = a.getColor(
				R.styleable.CalendarPickerView_headerTextColor,
				R.color.calendar_text_active);
		a.recycle();
		adapter = new MonthAdapter();
		setDivider(null);
		setDividerHeight(0);
		setBackgroundColor(bg);
		setCacheColorHint(bg);
		locale = Locale.getDefault();
		today = Calendar.getInstance(locale);
		minCal = Calendar.getInstance(locale);
		maxCal = Calendar.getInstance(locale);
		monthCounter = Calendar.getInstance(locale);
		monthNameFormat = new SimpleDateFormat(
				context.getString(R.string.month_name_format), locale);
		weekdayNameFormat = new SimpleDateFormat(
				context.getString(R.string.day_name_format), locale);
		fullDateFormat = DateFormat.getDateInstance(DateFormat.MEDIUM, locale);
		if (isInEditMode()) {
			Calendar nextYear = Calendar.getInstance(locale);
			nextYear.add(Calendar.YEAR, 1);
			init(new Date(), nextYear.getTime()) //
					.withSelectedDate(new Date());
		}
	}
	/**
	 * Both date parameters must be non-null and their {@link Date#getTime()}
	 * must not return 0. Time of day will be ignored. For instance, if you pass
	 * in {@code minDate} as 11/16/2012 5:15pm and {@code maxDate} as 11/16/2013
	 * 4:30am, 11/16/2012 will be the first selectable date and 11/15/2013 will
	 * be the last selectable date ({@code maxDate} is exclusive).
	 * <p>
	 * This will implicitly set the {@link SelectionMode} to
	 * {@link SelectionMode#SINGLE}. If you want a different selection mode, use
	 * {@link FluentInitializer#inMode(SelectionMode)} on the
	 * {@link FluentInitializer} this method returns.
	 * <p>
	 * The calendar will be constructed using the given locale. This means that
	 * all names (months, days) will be in the language of the locale and the
	 * weeks start with the day specified by the locale.
	 * 
	 * @param minDate
	 *            Earliest selectable date, inclusive. Must be earlier than
	 *            {@code maxDate}.
	 * @param maxDate
	 *            Latest selectable date, exclusive. Must be later than
	 *            {@code minDate}.
	 */
	public FluentInitializer init(Date minDate, Date maxDate, Locale locale) {
		if (minDate == null || maxDate == null) {
			throw new IllegalArgumentException(
					"minDate and maxDate must be non-null.  "
							+ dbg(minDate, maxDate));
		}
		if (minDate.after(maxDate)) {
			throw new IllegalArgumentException(
					"minDate must be before maxDate.  " + dbg(minDate, maxDate));
		}
		if (minDate.getTime() == 0 || maxDate.getTime() == 0) {
			throw new IllegalArgumentException(
					"minDate and maxDate must be non-zero.  "
							+ dbg(minDate, maxDate));
		}
		if (locale == null) {
			throw new IllegalArgumentException("Locale is null.");
		}
		// Make sure that all calendar instances use the same locale.
		this.locale = locale;
		today = Calendar.getInstance(locale);
		minCal = Calendar.getInstance(locale);
		maxCal = Calendar.getInstance(locale);
		monthCounter = Calendar.getInstance(locale);
		monthNameFormat = new SimpleDateFormat(getContext().getString(
				R.string.month_name_format), locale);
		for (MonthDescriptor month : months) {
			month.setLabel(monthNameFormat.format(month.getDate()));
		}
		weekdayNameFormat = new SimpleDateFormat(getContext().getString(
				R.string.day_name_format), locale);
		fullDateFormat = DateFormat.getDateInstance(DateFormat.MEDIUM, locale);
		this.selectionMode = SelectionMode.SINGLE;
		// Clear out any previously-selected dates/cells.
		selectedCals.clear();
		selectedCells.clear();
		highlightedCells.clear();
		// Clear previous state.
		cells.clear();
		months.clear();
		minCal.setTime(minDate);
		maxCal.setTime(maxDate);
		setMidnight(minCal);
		setMidnight(maxCal);
		displayOnly = false;
		// maxDate is exclusive: bump back to the previous day so if maxDate is
		// the first of a month,
		// we don't accidentally include that month in the view.
		maxCal.add(MINUTE, -1);
		// Now iterate between minCal and maxCal and build up our list of months
		// to show.
		monthCounter.setTime(minCal.getTime());
		final int maxMonth = maxCal.get(MONTH);
		final int maxYear = maxCal.get(YEAR);
		while ((monthCounter.get(MONTH) <= maxMonth // Up to, including the
													// month.
				|| monthCounter.get(YEAR) < maxYear) // Up to the year.
				&& monthCounter.get(YEAR) < maxYear + 1) { // But not > next yr.
			Date date = monthCounter.getTime();
			MonthDescriptor month = new MonthDescriptor(
					monthCounter.get(MONTH), monthCounter.get(YEAR), date,
					monthNameFormat.format(date));
			cells.add(getMonthCells(month, monthCounter));
			months.add(month);
			monthCounter.add(MONTH, 1);
		}
		validateAndUpdate();
		return new FluentInitializer();
	}
	/**
	 * Both date parameters must be non-null and their {@link Date#getTime()}
	 * must not return 0. Time of day will be ignored. For instance, if you pass
	 * in {@code minDate} as 11/16/2012 5:15pm and {@code maxDate} as 11/16/2013
	 * 4:30am, 11/16/2012 will be the first selectable date and 11/15/2013 will
	 * be the last selectable date ({@code maxDate} is exclusive).
	 * <p>
	 * This will implicitly set the {@link SelectionMode} to
	 * {@link SelectionMode#SINGLE}. If you want a different selection mode, use
	 * {@link FluentInitializer#inMode(SelectionMode)} on the
	 * {@link FluentInitializer} this method returns.
	 * <p>
	 * The calendar will be constructed using the default locale as returned by
	 * {@link java.util.Locale#getDefault()}. If you wish the calendar to be
	 * constructed using a different locale, use
	 * {@link #init(java.util.Date, java.util.Date, java.util.Locale)}.
	 * 
	 * @param minDate
	 *            Earliest selectable date, inclusive. Must be earlier than
	 *            {@code maxDate}.
	 * @param maxDate
	 *            Latest selectable date, exclusive. Must be later than
	 *            {@code minDate}.
	 */
	public FluentInitializer init(Date minDate, Date maxDate) {
		return init(minDate, maxDate, Locale.getDefault());
	}
	public class FluentInitializer {
		/**
		 * Override the {@link SelectionMode} from the default (
		 * {@link SelectionMode#SINGLE}).
		 */
		public FluentInitializer inMode(SelectionMode mode) {
			selectionMode = mode;
			validateAndUpdate();
			return this;
		}
		/**
		 * Set an initially-selected date. The calendar will scroll to that date
		 * if it's not already visible.
		 */
		public FluentInitializer withSelectedDate(Date selectedDates) {
			return withSelectedDates(Arrays.asList(selectedDates));
		}
		/**
		 * Set multiple selected dates. This will throw an
		 * {@link IllegalArgumentException} if you pass in multiple dates and
		 * haven't already called {@link #inMode(SelectionMode)}.
		 */
		public FluentInitializer withSelectedDates(
				Collection<Date> selectedDates) {
			if (selectionMode == SelectionMode.SINGLE
					&& selectedDates.size() > 1) {
				throw new IllegalArgumentException(
						"SINGLE mode can't be used with multiple selectedDates");
			}
			if (selectedDates != null) {
				for (Date date : selectedDates) {
					selectDate(date);
				}
			}
			scrollToSelectedDates();
			validateAndUpdate();
			return this;
		}
		public FluentInitializer withHighlightedDates(Collection<Date> dates) {
			highlightDates(dates);
			return this;
		}
		public FluentInitializer withHighlightedDate(Date date) {
			return withHighlightedDates(Arrays.asList(date));
		}
		public FluentInitializer displayOnly() {
			displayOnly = true;
			return this;
		}
	}
	private void validateAndUpdate() {
		if (getAdapter() == null) {
			setAdapter(adapter);
		}
		adapter.notifyDataSetChanged();
	}
	private void scrollToSelectedMonth(final int selectedIndex) {
		post(new Runnable() {
			@Override
			public void run() {
				setSelection(selectedIndex);
			}
		});
	}
	private void scrollToSelectedDates() {
		Integer selectedIndex = null;
		Integer todayIndex = null;
		Calendar today = Calendar.getInstance(locale);
		for (int c = 0; c < months.size(); c++) {
			MonthDescriptor month = months.get(c);
			if (selectedIndex == null) {
				for (Calendar selectedCal : selectedCals) {
					if (sameMonth(selectedCal, month)) {
						selectedIndex = c;
						break;
					}
				}
				if (selectedIndex == null && todayIndex == null
						&& sameMonth(today, month)) {
					todayIndex = c;
				}
			}
		}
		if (selectedIndex != null) {
			scrollToSelectedMonth(selectedIndex);
		} else if (todayIndex != null) {
			scrollToSelectedMonth(todayIndex);
		}
	}
	/**
	 * This method should only be called if the calendar is contained in a
	 * dialog, and it should only be called once, right after the dialog is
	 * shown (using {@link android.content.DialogInterface.OnShowListener} or
	 * {@link android.app.DialogFragment#onStart()}).
	 */
	public void fixDialogDimens() {
		// Fix the layout height/width after the dialog has been shown.
		getLayoutParams().height = getMeasuredHeight();
		getLayoutParams().width = getMeasuredWidth();
		// Post this runnable so it runs _after_ the dimen changes have been
		// applied/re-measured.
		post(new Runnable() {
			@Override
			public void run() {
				scrollToSelectedDates();
			}
		});
	}
	/**
	 * This method should only be called if the calendar is contained in a
	 * dialog, and it should only be called when the screen has been rotated and
	 * the dialog should be re-measured.
	 */
	public void unfixDialogDimens() {
		// Fix the layout height/width after the dialog has been shown.
		getLayoutParams().height = LayoutParams.MATCH_PARENT;
		getLayoutParams().width = LayoutParams.MATCH_PARENT;
		requestLayout();
	}
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		if (months.isEmpty()) {
			throw new IllegalStateException(
					"Must have at least one month to display.  Did you forget to call init()?");
		}
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
	}
	public Date getSelectedDate() {
		return (selectedCals.size() > 0 ? selectedCals.get(0).getTime() : null);
	}
	public List<Date> getSelectedDates() {
		List<Date> selectedDates = new ArrayList<Date>();
		for (MonthCellDescriptor cal : selectedCells) {
			selectedDates.add(cal.getDate());
		}
		Collections.sort(selectedDates);
		return selectedDates;
	}
	/** Returns a string summarizing what the client sent us for init() params. */
	private static String dbg(Date minDate, Date maxDate) {
		return "minDate: " + minDate + "\nmaxDate: " + maxDate;
	}
	/** Clears out the hours/minutes/seconds/millis of a Calendar. */
	static void setMidnight(Calendar cal) {
		cal.set(HOUR_OF_DAY, 0);
		cal.set(MINUTE, 0);
		cal.set(SECOND, 0);
		cal.set(MILLISECOND, 0);
	}
	private class CellClickedListener implements MonthView.Listener {
		@Override
		public void handleClick(MonthCellDescriptor cell) {
			Date clickedDate = cell.getDate();
			if (!betweenDates(clickedDate, minCal, maxCal)
					|| !isDateSelectable(clickedDate)) {
				if (invalidDateListener != null) {
					invalidDateListener.onInvalidDateSelected(clickedDate);
				}
			} else {
				boolean wasSelected = doSelectDate(clickedDate, cell);
				if (dateListener != null) {
					if (wasSelected) {
						dateListener.onDateSelected(clickedDate);
					} else {
						dateListener.onDateUnselected(clickedDate);
					}
				}
			}
		}
	}
	/**
	 * Select a new date. Respects the {@link SelectionMode} this
	 * CalendarPickerView is configured with: if you are in
	 * {@link SelectionMode#SINGLE}, the previously selected date will be
	 * un-selected. In {@link SelectionMode#MULTIPLE}, the new date will be
	 * added to the list of selected dates.
	 * <p>
	 * If the selection was made (selectable date, in range), the view will
	 * scroll to the newly selected date if it's not already visible.
	 * 
	 * @return - whether we were able to set the date
	 */
	public boolean selectDate(Date date) {
		validateDate(date);
		MonthCellWithMonthIndex monthCellWithMonthIndex = getMonthCellWithIndexByDate(date);
		if (monthCellWithMonthIndex == null || !isDateSelectable(date)) {
			return false;
		}
		boolean wasSelected = doSelectDate(date, monthCellWithMonthIndex.cell);
		if (wasSelected) {
			scrollToSelectedMonth(monthCellWithMonthIndex.monthIndex);
		}
		return wasSelected;
	}
	private void validateDate(Date date) {
		if (date == null) {
			throw new IllegalArgumentException(
					"Selected date must be non-null.");
		}
		if (date.getTime() == 0) {
			throw new IllegalArgumentException(
					"Selected date must be non-zero.  " + date);
		}
		if (date.before(minCal.getTime()) || date.after(maxCal.getTime())) {
			throw new IllegalArgumentException(String.format(
					"SelectedDate must be between minDate and maxDate."
							+ "%nminDate: %s%nmaxDate: %s%nselectedDate: %s",
					minCal.getTime(), maxCal.getTime(), date));
		}
	}
	private boolean doSelectDate(Date date, MonthCellDescriptor cell) {
		Calendar newlySelectedCal = Calendar.getInstance(locale);
		newlySelectedCal.setTime(date);
		// Sanitize input: clear out the hours/minutes/seconds/millis.
		setMidnight(newlySelectedCal);
		// Clear any remaining range state.
		for (MonthCellDescriptor selectedCell : selectedCells) {
			selectedCell.setRangeState(RangeState.NONE);
		}
		switch (selectionMode) {
		case RANGE:
			if (selectedCals.size() > 1) {
				// We've already got a range selected: clear the old one.
				clearOldSelections();
			} else if (selectedCals.size() == 1
					&& newlySelectedCal.before(selectedCals.get(0))) {
				// We're moving the start of the range back in time: clear the
				// old start date.
				clearOldSelections();
			}
			break;
		case MULTIPLE:
			date = applyMultiSelect(date, newlySelectedCal);
			break;
		case SINGLE:
			clearOldSelections();
			break;
		default:
			throw new IllegalStateException("Unknown selectionMode "
					+ selectionMode);
		}
		if (date != null) {
			// Select a new cell.
			if (selectedCells.size() == 0 || !selectedCells.get(0).equals(cell)) {
				selectedCells.add(cell);
				cell.setSelected(true);
			}
			selectedCals.add(newlySelectedCal);
			if (selectionMode == SelectionMode.RANGE
					&& selectedCells.size() > 1) {
				// Select all days in between start and end.
				Date start = selectedCells.get(0).getDate();
				Date end = selectedCells.get(1).getDate();
				selectedCells.get(0).setRangeState(
						MonthCellDescriptor.RangeState.FIRST);
				selectedCells.get(1).setRangeState(
						MonthCellDescriptor.RangeState.LAST);
				for (List<List<MonthCellDescriptor>> month : cells) {
					for (List<MonthCellDescriptor> week : month) {
						for (MonthCellDescriptor singleCell : week) {
							if (singleCell.getDate().after(start)
									&& singleCell.getDate().before(end)
									&& singleCell.isSelectable()) {
								singleCell.setSelected(true);
								singleCell
										.setRangeState(MonthCellDescriptor.RangeState.MIDDLE);
								selectedCells.add(singleCell);
							}
						}
					}
				}
			}
		}
		// Update the adapter.
		validateAndUpdate();
		return date != null;
	}
	private void clearOldSelections() {
		for (MonthCellDescriptor selectedCell : selectedCells) {
			// De-select the currently-selected cell.
			selectedCell.setSelected(false);
		}
		selectedCells.clear();
		selectedCals.clear();
	}
	private Date applyMultiSelect(Date date, Calendar selectedCal) {
		for (MonthCellDescriptor selectedCell : selectedCells) {
			if (selectedCell.getDate().equals(date)) {
				// De-select the currently-selected cell.
				selectedCell.setSelected(false);
				selectedCells.remove(selectedCell);
				date = null;
				break;
			}
		}
		for (Calendar cal : selectedCals) {
			if (sameDate(cal, selectedCal)) {
				selectedCals.remove(cal);
				break;
			}
		}
		return date;
	}
	public void highlightDates(Collection<Date> dates) {
		for (Date date : dates) {
			validateDate(date);
			MonthCellWithMonthIndex monthCellWithMonthIndex = getMonthCellWithIndexByDate(date);
			if (monthCellWithMonthIndex != null) {
				Calendar newlyHighlightedCal = Calendar.getInstance();
				newlyHighlightedCal.setTime(date);
				MonthCellDescriptor cell = monthCellWithMonthIndex.cell;
				highlightedCells.add(cell);
				highlightedCals.add(newlyHighlightedCal);
				cell.setHighlighted(true);
			}
		}
		adapter.notifyDataSetChanged();
		setAdapter(adapter);
	}
	/** Hold a cell with a month-index. */
	private static class MonthCellWithMonthIndex {
		public MonthCellDescriptor cell;
		public int monthIndex;
		public MonthCellWithMonthIndex(MonthCellDescriptor cell, int monthIndex) {
			this.cell = cell;
			this.monthIndex = monthIndex;
		}
	}
	/** Return cell and month-index (for scrolling) for a given Date. */
	private MonthCellWithMonthIndex getMonthCellWithIndexByDate(Date date) {
		int index = 0;
		Calendar searchCal = Calendar.getInstance(locale);
		searchCal.setTime(date);
		Calendar actCal = Calendar.getInstance(locale);
		for (List<List<MonthCellDescriptor>> monthCells : cells) {
			for (List<MonthCellDescriptor> weekCells : monthCells) {
				for (MonthCellDescriptor actCell : weekCells) {
					actCal.setTime(actCell.getDate());
					if (sameDate(actCal, searchCal) && actCell.isSelectable()) {
						return new MonthCellWithMonthIndex(actCell, index);
					}
				}
			}
			index++;
		}
		return null;
	}
	private class MonthAdapter extends BaseAdapter {
		private final LayoutInflater inflater;
		private MonthAdapter() {
			inflater = LayoutInflater.from(getContext());
		}
		@Override
		public boolean isEnabled(int position) {
			// Disable selectability: each cell will handle that itself.
			return false;
		}
		@Override
		public int getCount() {
			return months.size();
		}
		@Override
		public Object getItem(int position) {
			return months.get(position);
		}
		@Override
		public long getItemId(int position) {
			return position;
		}
		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			MonthView monthView = (MonthView) convertView;
			if (monthView == null) {
				monthView = MonthView.create(parent, inflater,
						weekdayNameFormat, listener, today, dividerColor,
						dayBackgroundResId, dayTextColorResId, titleTextColor,
						headerTextColor);
			}
			monthView.init(months.get(position), cells.get(position),
					displayOnly);
			return monthView;
		}
	}
	List<List<MonthCellDescriptor>> getMonthCells(MonthDescriptor month,
			Calendar startCal) {
		Calendar cal = Calendar.getInstance(locale);
		cal.setTime(startCal.getTime());
		List<List<MonthCellDescriptor>> cells = new ArrayList<List<MonthCellDescriptor>>();
		cal.set(DAY_OF_MONTH, 1);
		int firstDayOfWeek = cal.get(DAY_OF_WEEK);
		int offset = cal.getFirstDayOfWeek() - firstDayOfWeek;
		if (offset > 0) {
			offset -= 7;
		}
		cal.add(Calendar.DATE, offset);
		Calendar minSelectedCal = minDate(selectedCals);
		Calendar maxSelectedCal = maxDate(selectedCals);
		while ((cal.get(MONTH) < month.getMonth() + 1 || cal.get(YEAR) < month
				.getYear()) //
				&& cal.get(YEAR) <= month.getYear()) {
			List<MonthCellDescriptor> weekCells = new ArrayList<MonthCellDescriptor>();
			cells.add(weekCells);
			for (int c = 0; c < 7; c++) {
				Date date = cal.getTime();
				boolean isCurrentMonth = cal.get(MONTH) == month.getMonth();
				boolean isSelected = isCurrentMonth
						&& containsDate(selectedCals, cal);
				boolean isSelectable = isCurrentMonth
						&& betweenDates(cal, minCal, maxCal)
						&& isDateSelectable(date);
				boolean isToday = sameDate(cal, today);
				boolean isHighlighted = containsDate(highlightedCals, cal);
				int value = cal.get(DAY_OF_MONTH);
				MonthCellDescriptor.RangeState rangeState = MonthCellDescriptor.RangeState.NONE;
				if (selectedCals.size() > 1) {
					if (sameDate(minSelectedCal, cal)) {
						rangeState = MonthCellDescriptor.RangeState.FIRST;
					} else if (sameDate(maxDate(selectedCals), cal)) {
						rangeState = MonthCellDescriptor.RangeState.LAST;
					} else if (betweenDates(cal, minSelectedCal, maxSelectedCal)) {
						rangeState = MonthCellDescriptor.RangeState.MIDDLE;
					}
				}
				weekCells.add(new MonthCellDescriptor(date, isCurrentMonth,
						isSelectable, isSelected, isToday, isHighlighted,
						value, rangeState));
				cal.add(DATE, 1);
			}
		}
		return cells;
	}
	private static boolean containsDate(List<Calendar> selectedCals,
			Calendar cal) {
		for (Calendar selectedCal : selectedCals) {
			if (sameDate(cal, selectedCal)) {
				return true;
			}
		}
		return false;
	}
	private static Calendar minDate(List<Calendar> selectedCals) {
		if (selectedCals == null || selectedCals.size() == 0) {
			return null;
		}
		Collections.sort(selectedCals);
		return selectedCals.get(0);
	}
	private static Calendar maxDate(List<Calendar> selectedCals) {
		if (selectedCals == null || selectedCals.size() == 0) {
			return null;
		}
		Collections.sort(selectedCals);
		return selectedCals.get(selectedCals.size() - 1);
	}
	private static boolean sameDate(Calendar cal, Calendar selectedDate) {
		return cal.get(MONTH) == selectedDate.get(MONTH)
				&& cal.get(YEAR) == selectedDate.get(YEAR)
				&& cal.get(DAY_OF_MONTH) == selectedDate.get(DAY_OF_MONTH);
	}
	private static boolean betweenDates(Calendar cal, Calendar minCal,
			Calendar maxCal) {
		final Date date = cal.getTime();
		return betweenDates(date, minCal, maxCal);
	}
	static boolean betweenDates(Date date, Calendar minCal, Calendar maxCal) {
		final Date min = minCal.getTime();
		return (date.equals(min) || date.after(min)) // >= minCal
				&& date.before(maxCal.getTime()); // && < maxCal
	}
	private static boolean sameMonth(Calendar cal, MonthDescriptor month) {
		return (cal.get(MONTH) == month.getMonth() && cal.get(YEAR) == month
				.getYear());
	}
	private boolean isDateSelectable(Date date) {
		return dateConfiguredListener == null
				|| dateConfiguredListener.isDateSelectable(date);
	}
	public void setOnDateSelectedListener(OnDateSelectedListener listener) {
		dateListener = listener;
	}
	/**
	 * Set a listener to react to user selection of a disabled date.
	 * 
	 * @param listener
	 *            the listener to set, or null for no reaction
	 */
	public void setOnInvalidDateSelectedListener(
			OnInvalidDateSelectedListener listener) {
		invalidDateListener = listener;
	}
	/**
	 * Set a listener used to discriminate between selectable and unselectable
	 * dates. Set this to disable arbitrary dates as they are rendered.
	 * <p>
	 * Important: set this before you call {@link #init(Date, Date)} methods. If
	 * called afterwards, it will not be consistently applied.
	 */
	public void setDateSelectableFilter(DateSelectableFilter listener) {
		dateConfiguredListener = listener;
	}
	/**
	 * Interface to be notified when a new date is selected or unselected. This
	 * will only be called when the user initiates the date selection. If you
	 * call {@link #selectDate(Date)} this listener will not be notified.
	 * 
	 * @see #setOnDateSelectedListener(OnDateSelectedListener)
	 */
	public interface OnDateSelectedListener {
		void onDateSelected(Date date);
		void onDateUnselected(Date date);
	}
	/**
	 * Interface to be notified when an invalid date is selected by the user.
	 * This will only be called when the user initiates the date selection. If
	 * you call {@link #selectDate(Date)} this listener will not be notified.
	 * 
	 * @see #setOnInvalidDateSelectedListener(OnInvalidDateSelectedListener)
	 */
	public interface OnInvalidDateSelectedListener {
		void onInvalidDateSelected(Date date);
	}
	/**
	 * Interface used for determining the selectability of a date cell when it
	 * is configured for display on the calendar.
	 * 
	 * @see #setDateSelectableFilter(DateSelectableFilter)
	 */
	public interface DateSelectableFilter {
		boolean isDateSelectable(Date date);
	}
	private class DefaultOnInvalidDateSelectedListener implements
			OnInvalidDateSelectedListener {
		@Override
		public void onInvalidDateSelected(Date date) {
			String errMessage = getResources().getString(R.string.invalid_date,
					fullDateFormat.format(minCal.getTime()),
					fullDateFormat.format(maxCal.getTime()));
			Toast.makeText(getContext(), errMessage, Toast.LENGTH_SHORT).show();
		}
	}
}