1 /* 2 * Copyright (C) 2006 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.util; 18 19 import android.content.res.Resources; 20 import android.content.res.XmlResourceParser; 21 22 import org.apache.harmony.luni.internal.util.ZoneInfoDB; 23 import org.xmlpull.v1.XmlPullParser; 24 import org.xmlpull.v1.XmlPullParserException; 25 26 import java.io.IOException; 27 import java.util.TimeZone; 28 import java.util.Date; 29 30 import com.android.internal.util.XmlUtils; 31 32 /** 33 * A class containing utility methods related to time zones. 34 */ 35 public class TimeUtils { 36 private static final String TAG = "TimeUtils"; 37 38 /** 39 * Tries to return a time zone that would have had the specified offset 40 * and DST value at the specified moment in the specified country. 41 * Returns null if no suitable zone could be found. 42 */ getTimeZone(int offset, boolean dst, long when, String country)43 public static TimeZone getTimeZone(int offset, boolean dst, long when, String country) { 44 if (country == null) { 45 return null; 46 } 47 48 TimeZone best = null; 49 50 Resources r = Resources.getSystem(); 51 XmlResourceParser parser = r.getXml(com.android.internal.R.xml.time_zones_by_country); 52 Date d = new Date(when); 53 54 TimeZone current = TimeZone.getDefault(); 55 String currentName = current.getID(); 56 int currentOffset = current.getOffset(when); 57 boolean currentDst = current.inDaylightTime(d); 58 59 try { 60 XmlUtils.beginDocument(parser, "timezones"); 61 62 while (true) { 63 XmlUtils.nextElement(parser); 64 65 String element = parser.getName(); 66 if (element == null || !(element.equals("timezone"))) { 67 break; 68 } 69 70 String code = parser.getAttributeValue(null, "code"); 71 72 if (country.equals(code)) { 73 if (parser.next() == XmlPullParser.TEXT) { 74 String maybe = parser.getText(); 75 76 // If the current time zone is from the right country 77 // and meets the other known properties, keep it 78 // instead of changing to another one. 79 80 if (maybe.equals(currentName)) { 81 if (currentOffset == offset && currentDst == dst) { 82 return current; 83 } 84 } 85 86 // Otherwise, take the first zone from the right 87 // country that has the correct current offset and DST. 88 // (Keep iterating instead of returning in case we 89 // haven't encountered the current time zone yet.) 90 91 if (best == null) { 92 TimeZone tz = TimeZone.getTimeZone(maybe); 93 94 if (tz.getOffset(when) == offset && 95 tz.inDaylightTime(d) == dst) { 96 best = tz; 97 } 98 } 99 } 100 } 101 } 102 } catch (XmlPullParserException e) { 103 Log.e(TAG, "Got exception while getting preferred time zone.", e); 104 } catch (IOException e) { 105 Log.e(TAG, "Got exception while getting preferred time zone.", e); 106 } finally { 107 parser.close(); 108 } 109 110 return best; 111 } 112 113 /** 114 * Returns a String indicating the version of the time zone database currently 115 * in use. The format of the string is dependent on the underlying time zone 116 * database implementation, but will typically contain the year in which the database 117 * was updated plus a letter from a to z indicating changes made within that year. 118 * 119 * <p>Time zone database updates should be expected to occur periodically due to 120 * political and legal changes that cannot be anticipated in advance. Therefore, 121 * when computing the UTC time for a future event, applications should be aware that 122 * the results may differ following a time zone database update. This method allows 123 * applications to detect that a database change has occurred, and to recalculate any 124 * cached times accordingly. 125 * 126 * <p>The time zone database may be assumed to change only when the device runtime 127 * is restarted. Therefore, it is not necessary to re-query the database version 128 * during the lifetime of an activity. 129 */ getTimeZoneDatabaseVersion()130 public static String getTimeZoneDatabaseVersion() { 131 return ZoneInfoDB.getVersion(); 132 } 133 } 134