Java日历添加不递增年份

Question

我有一个存储周开始日期的变量，但是当我从 2012 年前进到 2013 年时，它不会更新年份。

日期和月份添加正确，因此它正确地从 26/12 到 02/01，但仍保留为 2012 年。

// roll one week forward
Calendar cal = Calendar.getInstance();
cal.setTimeInMillis(mPrefsHelper.getWeekStart());
cal.add(Calendar.WEEK_OF_YEAR, 1);

Answer 1

来自java.util.Calendar的javadoc

First Week

Calendar defines a locale-specific seven day week using two parameters: the first day of the week and the minimal days in firstweek (from 1 to 7). These numbers are taken from the locale resourcedata when a Calendar is constructed. They may also be specifiedexplicitly through the methods for setting their values.

When setting or getting the WEEK_OF_MONTH or WEEK_OF_YEAR fields, Calendar must determine the first week of the month or year as areference point. The first week of a month or year is defined as theearliest seven day period beginning on getFirstDayOfWeek() andcontaining at least getMinimalDaysInFirstWeek() days of that month oryear. Weeks numbered ..., -1, 0 precede the first week; weeks numbered2, 3,... follow it. Note that the normalized numbering returned byget() may be different. For example, a specific Calendar subclass maydesignate the week before week 1 of a year as week n of the previousyear.

它是特定于区域设置的。在您的情况下，如果该周包含新年后的天数，则将其计为新年后的第 1 周。