Android example source code file (MonthDisplayHelper.java)

This example Android source code file (MonthDisplayHelper.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

calendar, illegalargumentexception, monthdisplayhelper, util

The MonthDisplayHelper.java Android example source code

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.util;

import java.util.Calendar;

/**
 * Helps answer common questions that come up when displaying a month in a
 * 6 row calendar grid format.
 *
 * Not thread safe.
 */
public class MonthDisplayHelper {

    // display pref
    private final int mWeekStartDay;

    // holds current month, year, helps compute display
    private Calendar mCalendar;

    // cached computed stuff that helps with display
    private int mNumDaysInMonth;
    private int mNumDaysInPrevMonth;
    private int mOffset;


    /**
     * @param year The year.
     * @param month The month.
     * @param weekStartDay What day of the week the week should start.
     */
    public MonthDisplayHelper(int year, int month, int weekStartDay) {

        if (weekStartDay < Calendar.SUNDAY || weekStartDay > Calendar.SATURDAY) {
            throw new IllegalArgumentException();
        }
        mWeekStartDay = weekStartDay;

        mCalendar = Calendar.getInstance();
        mCalendar.set(Calendar.YEAR, year);
        mCalendar.set(Calendar.MONTH, month);
        mCalendar.set(Calendar.DAY_OF_MONTH, 1);
        mCalendar.set(Calendar.HOUR_OF_DAY, 0);
        mCalendar.set(Calendar.MINUTE, 0);
        mCalendar.set(Calendar.SECOND, 0);
        mCalendar.getTimeInMillis();

        recalculate();
    }


    public MonthDisplayHelper(int year, int month) {
        this(year, month, Calendar.SUNDAY);
    }


    public int getYear() {
        return mCalendar.get(Calendar.YEAR);
    }

    public int getMonth() {
        return mCalendar.get(Calendar.MONTH);
    }


    public int getWeekStartDay() {
        return mWeekStartDay;
    }

    /**
     * @return The first day of the month using a constants such as
     *   {@link java.util.Calendar#SUNDAY}.
     */
    public int getFirstDayOfMonth() {
        return mCalendar.get(Calendar.DAY_OF_WEEK);
    }

    /**
     * @return The number of days in the month.
     */
    public int getNumberOfDaysInMonth() {
        return mNumDaysInMonth;
    }


    /**
     * @return The offset from displaying everything starting on the very first
     *   box.  For example, if the calendar is set to display the first day of
     *   the week as Sunday, and the month starts on a Wednesday, the offset is 3.
     */
    public int getOffset() {
        return mOffset;
    }


    /**
     * @param row Which row (0-5).
     * @return the digits of the month to display in one
     * of the 6 rows of a calendar month display.
     */
    public int[] getDigitsForRow(int row) {
        if (row < 0 || row > 5) {
            throw new IllegalArgumentException("row " + row
                    + " out of range (0-5)");
        }

        int [] result = new int[7];
        for (int column = 0; column < 7; column++) {
            result[column] = getDayAt(row, column);
        }

        return result;
    }

    /**
     * @param row The row, 0-5, starting from the top.
     * @param column The column, 0-6, starting from the left.
     * @return The day at a particular row, column
     */
    public int getDayAt(int row, int column) {

        if (row == 0 && column < mOffset) {
            return mNumDaysInPrevMonth + column - mOffset + 1;
        }

        int day = 7 * row + column - mOffset + 1;

        return (day > mNumDaysInMonth) ?
                day - mNumDaysInMonth : day;
    }

    /**
     * @return Which row day is in.
     */
    public int getRowOf(int day) {
        return (day + mOffset - 1) / 7;
    }

    /**
     * @return Which column day is in.
     */
    public int getColumnOf(int day) {
        return (day + mOffset - 1) % 7;
    }

    /**
     * Decrement the month.
     */
    public void previousMonth() {
        mCalendar.add(Calendar.MONTH, -1);
        recalculate();
    }

    /**
     * Increment the month.
     */
    public void nextMonth() {
        mCalendar.add(Calendar.MONTH, 1);
        recalculate();
    }

    /**
     * @return Whether the row and column fall within the month.
     */
    public boolean isWithinCurrentMonth(int row, int column) {

        if (row < 0 || column < 0 || row > 5 || column > 6) {
            return false;
        }

        if (row == 0 && column < mOffset) {
            return false;
        }

        int day = 7 * row + column - mOffset + 1;
        if (day > mNumDaysInMonth) {
            return false;
        }
        return true;
    }


    // helper method that recalculates cached values based on current month / year
    private void recalculate() {

        mNumDaysInMonth = mCalendar.getActualMaximum(Calendar.DAY_OF_MONTH);

        mCalendar.add(Calendar.MONTH, -1);
        mNumDaysInPrevMonth = mCalendar.getActualMaximum(Calendar.DAY_OF_MONTH);
        mCalendar.add(Calendar.MONTH, 1);

        int firstDayOfMonth = getFirstDayOfMonth();
        int offset = firstDayOfMonth - mWeekStartDay;
        if (offset < 0) {
            offset += 7;
        }
        mOffset = offset;
    }
}