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/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.util;
import android.content.res.Resources;
import android.content.res.XmlResourceParser;
import org.apache.harmony.luni.internal.util.ZoneInfoDB;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import java.io.IOException;
import java.util.TimeZone;
import java.util.Date;
import com.android.internal.util.XmlUtils;
/**
* A class containing utility methods related to time zones.
*/
public class TimeUtils {
private static final String TAG = "TimeUtils";
/**
* Tries to return a time zone that would have had the specified offset
* and DST value at the specified moment in the specified country.
* Returns null if no suitable zone could be found.
*/
public static TimeZone getTimeZone(int offset, boolean dst, long when, String country) {
if (country == null) {
return null;
}
TimeZone best = null;
Resources r = Resources.getSystem();
XmlResourceParser parser = r.getXml(com.android.internal.R.xml.time_zones_by_country);
Date d = new Date(when);
TimeZone current = TimeZone.getDefault();
String currentName = current.getID();
int currentOffset = current.getOffset(when);
boolean currentDst = current.inDaylightTime(d);
try {
XmlUtils.beginDocument(parser, "timezones");
while (true) {
XmlUtils.nextElement(parser);
String element = parser.getName();
if (element == null || !(element.equals("timezone"))) {
break;
}
String code = parser.getAttributeValue(null, "code");
if (country.equals(code)) {
if (parser.next() == XmlPullParser.TEXT) {
String maybe = parser.getText();
// If the current time zone is from the right country
// and meets the other known properties, keep it
// instead of changing to another one.
if (maybe.equals(currentName)) {
if (currentOffset == offset && currentDst == dst) {
return current;
}
}
// Otherwise, take the first zone from the right
// country that has the correct current offset and DST.
// (Keep iterating instead of returning in case we
// haven't encountered the current time zone yet.)
if (best == null) {
TimeZone tz = TimeZone.getTimeZone(maybe);
if (tz.getOffset(when) == offset &&
tz.inDaylightTime(d) == dst) {
best = tz;
}
}
}
}
}
} catch (XmlPullParserException e) {
Log.e(TAG, "Got exception while getting preferred time zone.", e);
} catch (IOException e) {
Log.e(TAG, "Got exception while getting preferred time zone.", e);
} finally {
parser.close();
}
return best;
}
/**
* Returns a String indicating the version of the time zone database currently
* in use. The format of the string is dependent on the underlying time zone
* database implementation, but will typically contain the year in which the database
* was updated plus a letter from a to z indicating changes made within that year.
*
* <p>Time zone database updates should be expected to occur periodically due to
* political and legal changes that cannot be anticipated in advance. Therefore,
* when computing the UTC time for a future event, applications should be aware that
* the results may differ following a time zone database update. This method allows
* applications to detect that a database change has occurred, and to recalculate any
* cached times accordingly.
*
* <p>The time zone database may be assumed to change only when the device runtime
* is restarted. Therefore, it is not necessary to re-query the database version
* during the lifetime of an activity.
*/
public static String getTimeZoneDatabaseVersion() {
return ZoneInfoDB.getVersion();
}
}
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