从格林尼治标准​​时间值计算时区 - Android电子 [英] Calculating timezone from GMT value - Android

问题描述

在机器人的形式，我接受GMT值（偏移）从用户这样一个+5：30，+ 3：00。


从这个价值，我想计算时区是印度/新德里。

In a android form , i am accepting a GMT value(offset) from user such a +5:30 , +3:00.
and from this value , i want to calculate the timeZone that is "India/Delhi".

这是如何做到这一点的任何想法...... Plzz

Any ideas on how to do it ......Plzz

推荐答案

如果您已经在某一特定时刻着该偏移是有效的，你可以做这样的事情：

If you already have a specific instant in time at which that offset is valid, you could do something like this:

import java.util.*;

public class Test {

    public static void main(String [] args) throws Exception {
        // Five and a half hours
        int offsetMilliseconds = (5 * 60 + 30) * 60 * 1000;
        for (String id : findTimeZones(System.currentTimeMillis(),
                                       offsetMilliseconds)) {
            System.out.println(id);
        }
    }

    public static List<String> findTimeZones(long instant,
                                             int offsetMilliseconds) {
        List<String> ret = new ArrayList<String>();
        for (String id : TimeZone.getAvailableIDs()) {
            TimeZone zone = TimeZone.getTimeZone(id);
            if (zone.getOffset(instant) == offsetMilliseconds) {
                ret.add(id);
            }
        }
        return ret;
    }
}

在我的机器，打印：

Asia/Calcutta
Asia/Colombo
Asia/Kolkata
IST

（据我所知，印度/新德里不是一个有效的时区信息ID）。

(As far as I'm aware, India/Delhi isn't a valid zoneinfo ID.)

如果你不知道一个即时在该偏移是有效的，这变得相当难的真正的做正确。这里有一个版本：

If you don't know an instant at which the offset is valid, this becomes rather harder to really do properly. Here's one version:

public static List<String> findTimeZones(int offsetMilliseconds) {
    List<String> ret = new ArrayList<String>();
    for (String id : TimeZone.getAvailableIDs()) {
        TimeZone zone = TimeZone.getTimeZone(id);
        if (zone.getRawOffset() == offsetMilliseconds ||
            zone.getRawOffset() + zone.getDSTSavings() == offsetMilliseconds) {
            ret.add(id);
        }
    }
    return ret;
}

...但假定有每个时区只有永远两个偏移的时候，其实时区可以在历史相当大的变化。它也给你一个更广泛的ID，当然。例如，一小时的偏移将包括欧洲/伦敦和欧洲/巴黎，因为在夏季时间伦敦为UTC + 1，而在冬季巴黎是UTC + 1

... but that assumes that there are only ever two offsets per time zone, when in fact time zones can change considerably over history. It also gives you a much wider range of IDs, of course. For example, an offset of one hour would include both Europe/London and Europe/Paris, because in summer time London is at UTC+1, whereas in winter Paris is at UTC+1.

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