前陣子遇到一個需求：計算生日漫蛔。假設(shè)生日是2016年2月1號幕袱，那么我需要得到一個“1歲28天”的字符串访得。我沒想到j(luò)ava或者android API里有現(xiàn)成的方法可以計算州既，ios小哥表示他的api里有日歷的方法氮凝，可以通過那個去得到羔巢。我很郁悶，就去網(wǎng)上找，去api里找竿秆，找了半天也沒找到启摄，感覺找的功夫自己寫可能就寫完了，于是我就開始自己寫：

/**
 * 獲取生日
 * @param currentTime
 * @param birthTime
 * @return
 */
public static String getHomeBirthday(long currentTime, long birthTime){
    Calendar currentCalendar = Calendar.getInstance();
    currentCalendar.setTimeInMillis(currentTime);
    int currentYear = currentCalendar.get(Calendar.YEAR);
    int currentMonth = currentCalendar.get(Calendar.MONTH);
    int currentDay = currentCalendar.get(Calendar.DAY_OF_MONTH);

    Calendar birthCalendar = Calendar.getInstance();
    birthCalendar.setTimeInMillis(birthTime);
    int birthYear = birthCalendar.get(Calendar.YEAR);
    int birthMonth = birthCalendar.get(Calendar.MONTH);
    int birthDay = birthCalendar.get(Calendar.DAY_OF_MONTH);

    int year = 0;
    int month = 0;
    int day = 0;

    if(currentYear == birthYear){
        //生日為本年
        if(currentMonth == birthMonth){
            //當(dāng)前月份等于生日月份
            day = currentDay - birthDay + 1;
        }else{
            //當(dāng)前月份大于生日月份
            if(currentDay >= birthDay){
                //當(dāng)前天數(shù)不小于生日天數(shù)幽钢，天數(shù)為兩者之差
                day = (currentDay - birthDay) + 1;
                month = currentMonth - birthMonth;
            }else{
                //當(dāng)前天數(shù)小于生日天數(shù)歉备，天數(shù)為上月天數(shù)減去兩者之差， 月數(shù)減一
                day = getMonthOfDays(currentYear, currentMonth) - (birthDay - currentDay) + 1;
                month = currentMonth - birthMonth - 1;
            }
        }
    }else{
        //生日為往年
        if(currentMonth >= birthMonth){
            //當(dāng)前月份大于生日月份,年份為正常年差
            year = currentYear - birthYear;
            if(currentDay >= birthDay){
                //當(dāng)前天數(shù)大于生日天數(shù)匪燕，月份為正常月差蕾羊，天數(shù)為兩者之差
                day = (currentDay - birthDay) + 1;
                month = currentMonth - birthMonth;
            }else{
                day = getMonthOfDays(currentYear, currentMonth) - (birthDay - currentDay) + 1;
                month = currentMonth - birthMonth - 1;
            }
        }else{
            //當(dāng)前月份小于生日月份,年份差減一
            year = currentYear - birthYear - 1;
            if(currentDay >= birthDay){
                //當(dāng)前天數(shù)大于生日天數(shù)，月份為正常月差帽驯，天數(shù)為兩者之差
                day = (currentDay - birthDay) + 1;
                month = 12 - (birthMonth - currentMonth);
            }else{
                day = getMonthOfDays(currentYear, currentMonth) - (birthDay - currentDay) + 1;
                month = 12 - (birthMonth - currentMonth) - 1;
            }
        }
    }
    String yearStr = "";
    String monthStr = "";
    String dayStr = "";
    if(year > 0){
        yearStr = year + "歲";
    }
    if(month > 0){
        monthStr = month + "個月";
    }
    if(day > 0){
        dayStr = day + "天";
    }
    return yearStr + monthStr + dayStr;
}

/**
 * 獲取指定月份的天數(shù)
 *
 * @param year
 * @param month
 * @return
 */
public static int getMonthOfDays(int year, int month) {
    Calendar calendar = Calendar.getInstance();
    calendar.set(Calendar.YEAR, year);
    calendar.set(Calendar.MONTH, month - 1);
    calendar.set(Calendar.DATE, 1);
    calendar.roll(Calendar.DATE, -1);
    return calendar.get(Calendar.DATE);
}

把這個方法放上來是因?yàn)槲腋杏X還有可以改進(jìn)的地方龟再。如果您發(fā)現(xiàn)有可以改進(jìn)的地方或是有更方便的系統(tǒng)api方法，請告知尼变，感激不盡利凑！

2017.4.5修改

現(xiàn)在看太糙了，修改了一下：

/**
 * 獲取生日
 *
 * @param currentTime
 * @param birthTime
 * @return
 */
public static String getHomeBirthday(long currentTime, long birthTime) {
    Calendar currentCalendar = Calendar.getInstance();
    currentCalendar.setTimeInMillis(currentTime);
    int currentYear = currentCalendar.get(Calendar.YEAR);
    int currentMonth = currentCalendar.get(Calendar.MONTH);
    int currentDay = currentCalendar.get(Calendar.DAY_OF_MONTH);

    Calendar birthCalendar = Calendar.getInstance();
    birthCalendar.setTimeInMillis(birthTime);
    int birthYear = birthCalendar.get(Calendar.YEAR);
    int birthMonth = birthCalendar.get(Calendar.MONTH);
    int birthDay = birthCalendar.get(Calendar.DAY_OF_MONTH);

    int year = 0;
    int month = 0;
    int day = 0;

    day = currentDay - birthDay;
    if(day <= 0){
        day = getMonthOfDays(currentYear, currentMonth) - birthDay + currentDay;
        month = -1;
    }

    month += currentMonth - birthMonth;
    if(month < 0){
        month = 12 + month;
        year = -1;
    }

    year += currentYear - birthYear;

    if (year > 0) {
        return year + "歲" + month + "個月" + day + "天";
    }
    if (month > 0) {
        return month + "個月" + day + "天";
    } else {
        return day + "天";
    }
}

/**
 * 獲取指定月份的天數(shù)
 *
 * @param year
 * @param month
 * @return
 */
public static int getMonthOfDays(int year, int month) {
    Calendar calendar = Calendar.getInstance();
    calendar.set(Calendar.YEAR, year);
    calendar.set(Calendar.MONTH, month - 1);
    calendar.set(Calendar.DATE, 1);
    calendar.roll(Calendar.DATE, -1);
    return calendar.get(Calendar.DATE);
}