Question

我有以下代码来获取当前日期之前的最后一个星期日：

Calendar calendar=Calendar.getInstance();
calendar.set(Calendar.WEEK_OF_YEAR, calendar.get(Calendar.WEEK_OF_YEAR)-1);
calendar.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
Log.e("first day", String.valueOf(calendar.get(Calendar.DAY_OF_MONTH)));

但是这段代码不起作用。请告诉我，我该如何解决？

Answer 1

这会奏效。我们首先获得日期计数，然后在当天减去该数量并添加1（对于星期日）

Calendar cal=Calendar.getInstance();
cal.add( Calendar.DAY_OF_WEEK, -(cal.get(Calendar.DAY_OF_WEEK)-1)); 
System.out.println(cal.get(Calendar.DATE));

Answer 2

这可以通过TemporalAdjusters（仅限Java 8+）轻松实现。

 LocalDate.now().with(TemporalAdjusters.previous(DayOfWeek.SUNDAY))

如果今天是星期天，你想得到当天，那么：

 LocalDate.now().with(TemporalAdjusters.previousOrSame(DayOfWeek.SUNDAY))

Answer 3

你可以在一天的步骤中迭代，直到你到达星期天：

Calendar cal = Calendar.getInstance();
while (cal.get( Calendar.DAY_OF_WEEK ) != Calendar.SUNDAY)
    cal.add( Calendar.DAY_OF_WEEK, -1 );

或者，只需一步，减去星期日和现在之间的天数差异：

Calendar cal = Calendar.getInstance();
int dayOfTheWeek = cal.get( Calendar.DAY_OF_WEEK );
cal.add( Calendar.DAY_OF_WEEK, Calendar.SUNDAY - dayOfTheWeek );

Answer 4

以下是使用Joda计算一周最后一天的片段：

import org.joda.time.DateTime
import org.joda.time.DateTimeConstants

DateTime now = DateTime();
int offset = ((now.dayOfWeek - DateTimeConstants.THURSDAY) + 7) % 7;
DateTime lastThursday = now.minusDays(offset);

只需将DateTimeConstants.THURSDAY替换为您选择的日期。

Answer 5

final Calendar cal = Calendar.getInstance();
cal.setTimeInMillis(cal.getTimeInMillis() //
     // Saturday is the 7th day of week, so use modulo to get it : remove day between todoay
     - (( cal.get(Calendar.DAY_OF_WEEK) % 7) * 86400000)); // 86400000=24*60*60*1000

System.out.println(cal.getTime());
. . .

Answer 6

以下适用于我，无论是哪个月份。

 Calendar cal = Calendar.getInstance(TimeZone.getDefault());
 Date date = cal.getTime();
 int days = cal.get(Calendar.DAY_OF_WEEK) - Calendar.SUNDAY;
 date.setTime(date.getTime() - (long) (days*1000*60*60*24));
 cal.setTime(date);

Answer 7

以下是使用Kotlin扩展名和Joda Time library的方法。
答案基于linqu的答案，但这也修复了该答案中的错误。该错误是，如果当前日期与您尝试获取的日期相同，则该日期不起作用。

/**
 * E.g., DateTimeConstants.SUNDAY
 */
fun DateTime.previousDayOfWeek(day: Int): DateTime {
    var date = this
    if(date.dayOfWeek == day) date = date.minusDays(1)

    val offset = (date.dayOfWeek - day + 7) % 7
    return date.minusDays(offset)
}

fun DateTime.previousSunday(): DateTime {
    return previousDayOfWeek(DateTimeConstants.SUNDAY)
}

如何获得当前日期之前的最后一个星期天？

7 个答案: