Java 将日历设置为特定日期？
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Set the Calendar to a specific date?
提问by user1579019
I want to set a reminder with notification on a specific date. Then I am using AlarmManager with NotificationManager currently. When I set selected date from dateDialog, the reminder is working. How can I put calendar value on alarm set with fixed time? I get the current date and time from this :
我想在特定日期设置带有通知的提醒。然后我目前正在将 AlarmManager 与 NotificationManager 一起使用。当我从 dateDialog 设置选定的日期时，提醒正在工作。如何在固定时间设置的闹钟上放置日历值？我从中获取当前日期和时间：
Calendar calendar = Calendar.getInstance();
and then I can set the calendar manually like below and it's working:
然后我可以像下面一样手动设置日历并且它正在工作：
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MINUTE, 13);
calendar.set(Calendar.HOUR, 7);
calendar.set(Calendar.AM_PM, Calendar.AM);
calendar.set(Calendar.MONTH, Calendar.JANUARY);
calendar.set(Calendar.DAY_OF_MONTH, 8);
calendar.set(Calendar.YEAR,2015);
long when = calendar.getTimeInMillis();
But my question is how can I set the calendar to tomorrow and 9:00 AM or set the calendar exactly to a particular month (or year) later from the current date? I mean something like this :
但我的问题是如何将日历设置为明天和上午 9:00，或者如何将日历设置为当前日期之后的特定月份（或年份）？我的意思是这样的：
calendar.add(Calendar.DAY_OF_MONTH, 1);
but it does not work.
但它不起作用。
采纳答案by Basil Bourque
Joda-Time
乔达时间
UPDATE:The Joda-Timeproject is now in maintenance mode, with the team advising migration to the java.timeclasses. See Tutorial by Oracle.
UPDATE：该乔达时间的项目现在处于维护模式，与团队的建议迁移java.time类。请参阅Oracle 教程。
Try using a better date-time library, such as Joda-Time.
尝试使用更好的日期时间库，例如 Joda-Time。
In Joda-Time you can change the date while keeping the time of day. Or, vice-versa, keep the time of day while keeping the date.
在 Joda-Time 中，您可以在保留时间的同时更改日期。或者，反之亦然，在保留日期的同时保留时间。
DateTime now = DateTime.now( DateTimeZone.forID( "America/Montreal" ) ) ;
DateTime todayNoon = now.withTime( 12, 0, 0, 0 ) ;
DateTime midMarchSameYearSameTimeAsNow = now.withDate( now.getYear(), DateTimeConstants.MARCH, 15 );
DateTime tomorrowSameTime = now.plusDays( 1 );
回答by Tr4X
To add an hour by example, you can do something like this :
要通过示例添加一个小时，您可以执行以下操作：
calendar.set(Calendar.HOUR, calendar.get(Calendar.HOUR) + 1);
回答by tringel
For me this works just fine on the desktop, couldn't test it on Android though.
Update:just tested this on my Android phone using AIDE, getting the exact same results.
对我来说，这在桌面上工作得很好，但无法在 Android 上进行测试。
更新：刚刚使用 AIDE 在我的 Android 手机上对此进行了测试，得到了完全相同的结果。
import java.util.Calendar;
public class CalendarTest {
public static void main(String[] args) {
Calendar calendar = Calendar.getInstance();
System.out.println(calendar.getTimeInMillis() + " -> " + calendar.getTime());
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MINUTE, 13);
calendar.set(Calendar.HOUR, 7);
calendar.set(Calendar.AM_PM, Calendar.AM);
calendar.set(Calendar.MONTH, Calendar.JANUARY);
calendar.set(Calendar.DAY_OF_MONTH, 9);
calendar.set(Calendar.YEAR, 2015);
System.out.println(calendar.getTimeInMillis() + " -> " + calendar.getTime());
calendar.add(Calendar.DAY_OF_MONTH, 1);
calendar.add(Calendar.YEAR, 1);
System.out.println(calendar.getTimeInMillis() + " -> " + calendar.getTime());
}
For this test my output is just what you would expect:
对于此测试，我的输出正是您所期望的：
1420705649927 -> Thu Jan 08 09:27:29 CET 2015
1420783980927 -> Fri Jan 09 07:13:00 CET 2015
1452406380927 -> Sun Jan 10 07:13:00 CET 2016
回答by Basil Bourque
tl;dr
tl;博士
ZonedDateTime.of(
LocalDate.of( 2015 , Month.JANUARY , 8 ) ,
LocalTime.of( 7 , 13 , 0 ) ,
ZoneId.of( "Africa/Tunis" )
)
.toInstant()
.toEpochMilli()
1420697580000
1420697580000
java.time
时间
The modern approach uses the java.timeclasses that supplant the troublesome old legacy date-time classes. Somuch easier and cleaner now.
现代方法使用java.time类来取代麻烦的旧的遗留日期时间类。所以，现在更容易和更清洁。
Your code is ambiguous, as you do not address the crucial issue of time zone. As you did not specify a time zone explicitly, your JVM's current default time zone will be applied implicitly. I strongly recommend alwaysspecifying your desired/expected time zone.
您的代码含糊不清，因为您没有解决时区的关键问题。由于您没有明确指定时区，您的 JVM 当前默认时区将被隐式应用。我强烈建议始终指定您想要/预期的时区。
Specify a proper time zone namein the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter pseudo-zones such as ESTor ISTas they are nottrue time zones, not standardized, and not even unique(!).
以、、 或等格式指定正确的时区名称。永远不要使用 3-4 个字母的伪区域，例如或因为它们不是真正的时区，不是标准化的，甚至不是唯一的（！）。continent/regionAmerica/MontrealAfrica/CasablancaPacific/AucklandESTIST
LocalDate ld = LocalDate.of( 2015 , Month.JANUARY , 8 ) ;
LocalTime lt = LocalTime.of( 7 , 13 , 0 ) ;
ZoneId z = ZoneId.of( "Pacific/Auckland" ) ;
ZonedDateTime zdt = ZonedDateTime.of( ld , lt , z ) ;
You could use a combo factor method, alternatively.
或者，您可以使用组合因子方法。
ZonedDateTime zdt = ZonedDateTime.of( 2015 , Month.JANUARY , 8 , 7 , 13 , 0 , 0 , ZoneId.of( "Pacific/Auckland" ) ) ;
I generally recommend against tracking date-time as a count-from-epoch. But it seems to be requirement in your case.
我通常建议不要将日期时间作为从纪元开始的计数。但这似乎是您的要求。
First we can extract a Instant, a moment in UTC. The Instantclass represents a moment on the timeline in UTCwith a resolution of nanoseconds(up to nine (9) digits of a decimal fraction).
首先，我们可以Instant在 UTC 中提取一个时刻。该Instant级表示时间轴上的时刻UTC，分辨率为纳秒（最多小数的9个位数）。
Instant instant = zdt.toInstant() ; // Convert from a zoned value to a UTC value.
You can then ask for the count of milliseconds since the epoch reference of first moment of 1970 in UTC, 1970-01-01T00:00:00Z. Beware of possible data loss, as any microseconds or nanoseconds in the Instantwill be ignored when reporting mere milliseconds.
然后，您可以询问自 UTC 中 1970 年第一时刻的纪元参考以来的毫秒数，即 1970-01-01T00:00:00Z。当心可能的数据丢失，因为Instant在报告仅毫秒时将忽略任何微秒或纳秒。
long millis = instant.toEpochMilli() ; // Count of milliseconds since 1970-01-01T00:00:00Z.
About java.time
关于java.time
The java.timeframework is built into Java 8 and later. These classes supplant the troublesome old legacydate-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
该java.time框架是建立在Java 8和更高版本。这些类取代了麻烦的旧的遗留日期时间类，例如java.util.Date, Calendar, & SimpleDateFormat。
The Joda-Timeproject, now in maintenance mode, advises migration to the java.timeclasses.
现在处于维护模式的Joda-Time项目建议迁移到java.time类。
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
要了解更多信息，请参阅Oracle 教程。并在 Stack Overflow 上搜索许多示例和解释。规范是JSR 310。
Using a JDBC drivercompliant with JDBC 4.2or later, you may exchange java.timeobjects directly with your database. No need for strings nor java.sql.* classes.
使用符合JDBC 4.2或更高版本的JDBC 驱动程序，您可以直接与您的数据库交换java.time对象。不需要字符串或 java.sql.* 类。
Where to obtain the java.time classes?
从哪里获得 java.time 类？
- Java SE 8, Java SE 9, and later
- Built-in.
- Part of the standard Java API with a bundled implementation.
- Java 9 adds some minor features and fixes.
- Java SE 6and Java SE 7
- Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
- Android
- Later versions of Android bundle implementations of the java.time classes.
- For earlier Android, the ThreeTenABPproject adapts ThreeTen-Backport(mentioned above). See How to use ThreeTenABP….
- Java SE 8、Java SE 9及更高版本
- 内置。
- 具有捆绑实现的标准 Java API 的一部分。
- Java 9 添加了一些小功能和修复。
- Java SE 6和Java SE 7
- 多的java.time功能后移植到Java 6和7在ThreeTen-反向移植。
- 安卓
- java.time 类的更高版本的 Android 捆绑实现。
- 对于早期的 Android，ThreeTenABP项目采用了ThreeTen-Backport（上面提到过）。请参阅如何使用ThreeTenABP ...。
The ThreeTen-Extraproject extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.
该ThreeTen-额外项目与其他类扩展java.time。该项目是未来可能添加到 java.time 的试验场。你可能在这里找到一些有用的类，比如Interval，YearWeek，YearQuarter，和更多。
