关于GregorianCalendar这个类

i風 2018-05-31 02:03:45

刚开始是2017-8-31，然后我连续加了3次，一次加3个月，前两个次输出的是正确的但是为啥到第三次出现了28天这种问题？
是因为经过了2月导致的？试了一下将第一次改成+6然后第二次与第三次都变成了28天？哪位大神指导这是什么问题吗？如何解决？

Calendar cal = new GregorianCalendar();
LogUtils.e(DateUtils.StringToDateString(in.BuyTime));//2017-8-31
cal.setTime(DateUtils.Parse2Date(DateUtils.StringToDateString(in.BuyTime),"yyyy-MM-dd"));
//当前月份+3个月
cal.add(Calendar.MONTH, +3);
long date3 = (cal.getTimeInMillis()-dateNow.getTime() );
Log.e("TAG",cal.getTimeInMillis()+"");//2017-11-30 00:00:00
cal.add(Calendar.MONTH, +3);
long date6 = (cal.getTimeInMillis()-dateNow.getTime() );
Log.e("TAG",cal.getTimeInMillis()+"");//2018-02-28 00:00:00
cal.add(Calendar.MONTH, +3);
long date9 = (cal.getTimeInMillis()-dateNow.getTime());
Log.e("TAG",cal.getTimeInMillis()+"");//2018-05-28 00:00:00

...全文

1504 6 打赏收藏转发到动态举报

写回复

用AI写文章

6 条回复

切换为时间正序

请发表友善的回复…

发表回复

阿飞__ 2018-06-09

打赏
举报

引用 5 楼 Hard_F 的回复:

[quote=引用 4 楼 afei__ 的回复:]
    /**
     * After adjustments such as add(MONTH), add(YEAR), we don't want the
     * month to jump around.  E.g., we don't want Jan 31 + 1 month to go to Mar
     * 3, we want it to go to Feb 28.  Adjustments which might run into this
     * problem call this method to retain the proper month.
     */
    private final void pinDayOfMonth() {
        int year = internalGet(YEAR);
        int monthLen;
        if (year > gregorianCutoverYear || year < gregorianCutoverYearJulian) {
            monthLen = monthLength(internalGet(MONTH));
        } else {
            GregorianCalendar gc = getNormalizedCalendar();
            monthLen = gc.getActualMaximum(DAY_OF_MONTH);
        }
        int dom = internalGet(DAY_OF_MONTH);
        if (dom > monthLen) {
            set(DAY_OF_MONTH, monthLen);
        }
    }
这是GregorianCalendar源码里的描述，当1月31，加一个月时，是希望跳到的就是2月28。其次，代码逻辑里面有这样的判断，monthLen 是一个月的最大天数，但 dom > monthLen 时，当月的天数就被设为最大天数了，避免出现2月31这样的情况。这样理解了吧

那这样该怎么使日期正常显示呢，就经过2月后3月或5月，让其正常显示？[/quote] 那只能自己去判断天数了。系统代码里的逻辑就是，你1月31号加一个月，这里的一个月刚好是2月，2月只有28天，就是2月28了，2月28加一个月，肯定是3月28，不可能给你涨到3月31。你想要都是每个月的最大天数，就只能自己去根据 dayOfMonth 这个值去自己修改了

i風 2018-06-08

打赏
举报

引用 4 楼 afei__ 的回复:

    /**
     * After adjustments such as add(MONTH), add(YEAR), we don't want the
     * month to jump around.  E.g., we don't want Jan 31 + 1 month to go to Mar
     * 3, we want it to go to Feb 28.  Adjustments which might run into this
     * problem call this method to retain the proper month.
     */
    private final void pinDayOfMonth() {
        int year = internalGet(YEAR);
        int monthLen;
        if (year > gregorianCutoverYear || year < gregorianCutoverYearJulian) {
            monthLen = monthLength(internalGet(MONTH));
        } else {
            GregorianCalendar gc = getNormalizedCalendar();
            monthLen = gc.getActualMaximum(DAY_OF_MONTH);
        }
        int dom = internalGet(DAY_OF_MONTH);
        if (dom > monthLen) {
            set(DAY_OF_MONTH, monthLen);
        }
    }

这是GregorianCalendar源码里的描述，当1月31，加一个月时，是希望跳到的就是2月28。其次，代码逻辑里面有这样的判断，monthLen 是一个月的最大天数，但 dom > monthLen 时，当月的天数就被设为最大天数了，避免出现2月31这样的情况。这样理解了吧

那这样该怎么使日期正常显示呢，就经过2月后3月或5月，让其正常显示？

阿飞__ 2018-06-04

打赏
举报

    /**
     * After adjustments such as add(MONTH), add(YEAR), we don't want the
     * month to jump around.  E.g., we don't want Jan 31 + 1 month to go to Mar
     * 3, we want it to go to Feb 28.  Adjustments which might run into this
     * problem call this method to retain the proper month.
     */
    private final void pinDayOfMonth() {
        int year = internalGet(YEAR);
        int monthLen;
        if (year > gregorianCutoverYear || year < gregorianCutoverYearJulian) {
            monthLen = monthLength(internalGet(MONTH));
        } else {
            GregorianCalendar gc = getNormalizedCalendar();
            monthLen = gc.getActualMaximum(DAY_OF_MONTH);
        }
        int dom = internalGet(DAY_OF_MONTH);
        if (dom > monthLen) {
            set(DAY_OF_MONTH, monthLen);
        }
    }

阿飞__ 2018-06-04