从设备获取当前时间毫秒，并将其转换为具有不同时区的新日期 [英] Getting the current time millis from device and converting it into a new date with different timezone

问题描述

这里我面临的问题是-

首先，我创建了一个date对象，它将为我提供设备时区的当前日期和时间，即

First i have created a date object which will give me current date and time with device timezone i.e

Date date = new Date(); // Let say the time zone is India - GMT (+05:30)
The value of date is = "Mon Sep 24 13:54:06 GMT+05:30 2018"

不，我有一个Date格式化程序，使用它我转换了以下日期对象。

No i have a Date formatter using which i have converted the following date object.

SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss z");
sdf.setTimeZone(TimeZone.getTimeZone(loadPreferences(Utility.TIMEZONE_NAME)));
// Here the timezone is Hawaii (GMT-10:00)

现在按照新时区的时间，即夏威夷

Now getting the time as per the new time zone i.e., Hawaii

String dateS = sdf.format(date); 
// This will give you the date with new timezone - "2018/09/23 22:24:06 GMT-10:00"

现在将此字符串日期转换为日期对象为-

Now converting this string date to date object as -

Date newDate = sdf.parse(dateS);

现在我所获得的新日期与我过去的时区不同。

Now the new date which i'm getting is not as per the timezone which i have passed.

The value of newDate which i'm getting is = "Mon Sep 24 13:54:06 GMT+05:30 2018" 
//This is device timezone not the one i have set.

我已经尝试过 Z， z， X， ZZ，日期格式器中的ZZZZZ仍然没有运气。

I have already tried "Z", "z", "X", "ZZ", "ZZZZZ" in the date formatter still no luck.

如果您有任何想法阅读此书，请告诉我。

If any of you have any idea reading this then let me know.

推荐答案

两条消息：

• 您的期望是错误的。 日期没有时区，所以没有。因此，无论您如何编写代码，都无法使用 Date 和 SimpleDateFormat 来获取。


• Date ， SimpleDateFormat 和 TimeZone 早已过时且设计欠佳。它们的现代替代品是在2014年引入的java.time（日期和时间API）中。

• Your expectations are wrong. A Date hasn’t got a time zone, it cannot have. So what you are trying to obtain is impossible using Date and SimpleDateFormat no matter how you write the code.
• The classes Date, SimpleDateFormat and TimeZone are long outdated and poorly designed. Their modern replacements are in java.time, the date and time API introduced in 2014.

现代的 ZonedDateTime 具有时区，顾名思义：

A modern ZonedDateTime has a time zone as the name says:

    DateTimeFormatter formatter 
            = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss z", Locale.US);
    ZonedDateTime nowInHawaii = ZonedDateTime.now(ZoneId.of("Pacific/Honolulu"));
    String dateS = nowInHawaii.format(formatter);
    System.out.println(dateS);

此代码段的输出为：

2018/09/24 18:43:19 HST

2018/09/24 18:43:19 HST

如果要在输出中使用偏移量，从而更改格式器：

If you want the offset in the output, change the formatter thusly:

    DateTimeFormatter formatter 
            = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss OOOO", Locale.US);

2018/09/24 18:45:53 GMT-10： 00

2018/09/24 18:45:53 GMT-10:00

问题：我可以在Android上使用 java.time 吗？

是的， java.time 在较新的Android设备上都能很好地工作。它只需要至少 Java 6 。

Question: Can I use java.time on Android?

Yes, java.time works nicely on older and newer Android devices. It just requires at least Java 6.

• 在Java 8和更高版本以及新的Android设备上（通过API）有人告诉我，第26级是内置的现代API。


• 在Java 6和7中，获得了ThreeTen Backport，这是现代类的Backport（JSR 310的ThreeTen，其中


• 在（较旧的）Android上，使用Android版的ThreeTen Backport。叫做ThreeTenABP。确保从包 org.threeten.bp 和子包中导入日期和时间类。

• In Java 8 and later and on new Android devices (from API level 26, I’m told) the modern API comes built-in.
• In Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310, where the modern API was first described).
• On (older) Android, use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. Make sure you import the date and time classes from package org.threeten.bp and subpackages.

• Oracle教程：日期时间，说明了如何使用 java.time 。


• < a href = http://www.threeten.org/threetenbp/ rel = nofollow noreferrer> ThreeTen Backport项目


• ThreeTenABP ，ThreeTen Backport的Android版本


• 问题：如何在Android Project中使用ThreeTenABP ，并有非常详尽的解释。


• Java规范请求（JSR）310 。

• Oracle tutorial: Date Time, explaining how to use java.time.
• ThreeTen Backport project
• ThreeTenABP, Android edition of ThreeTen Backport
• Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.
• Java Specification Request (JSR) 310.

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