Merge "API for retrieving time zone IDs by country"

api/current.txt

@@ -46255,6 +46255,7 @@ package android.util {
   public class TimeUtils {
     method public static java.util.TimeZone getTimeZone(int, boolean, long, java.lang.String);
     method public static java.lang.String getTimeZoneDatabaseVersion();
+    method public static java.util.List<java.lang.String> getTimeZoneIdsForCountryCode(java.lang.String);
   }
 
   public class TimingLogger {

core/java/android/util/TimeUtils.java

@@ -16,16 +16,24 @@
 
 package android.util;
 
+import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.UnsupportedAppUsage;
 import android.os.SystemClock;
 
+import libcore.util.CountryTimeZones;
+import libcore.util.CountryTimeZones.TimeZoneMapping;
 import libcore.util.TimeZoneFinder;
 import libcore.util.ZoneInfoDB;
 
 import java.io.PrintWriter;
 import java.text.SimpleDateFormat;
+import java.util.ArrayList;
 import java.util.Calendar;
+import java.util.Collections;
 import java.util.Date;
+import java.util.List;
+
 /**
  * A class containing utility methods related to time zones.
  */
@@ -64,6 +72,38 @@ public class TimeUtils {
                 .lookupTimeZoneByCountryAndOffset(country, offset, dst, when, bias);
     }
 
+    /**
+     * Returns time zone IDs for time zones known to be associated with a country.
+     *
+     * <p>The list returned may be different from other on-device sources like
+     * {@link android.icu.util.TimeZone#getRegion(String)} as it can be curated to avoid
+     * contentious mappings.
+     *
+     * @param countryCode the ISO 3166-1 alpha-2 code for the country as can be obtained using
+     *     {@link java.util.Locale#getCountry()}
+     * @return IDs that can be passed to {@link java.util.TimeZone#getTimeZone(String)} or similar
+     *     methods, or {@code null} if the countryCode is unrecognized
+     */
+    public static @Nullable List<String> getTimeZoneIdsForCountryCode(@NonNull String countryCode) {
+        if (countryCode == null) {
+            throw new NullPointerException("countryCode == null");
+        }
+        TimeZoneFinder timeZoneFinder = TimeZoneFinder.getInstance();
+        CountryTimeZones countryTimeZones =
+                timeZoneFinder.lookupCountryTimeZones(countryCode.toLowerCase());
+        if (countryTimeZones == null) {
+            return null;
+        }
+
+        List<String> timeZoneIds = new ArrayList<>();
+        for (TimeZoneMapping timeZoneMapping : countryTimeZones.getTimeZoneMappings()) {
+            if (timeZoneMapping.showInPicker) {
+                timeZoneIds.add(timeZoneMapping.timeZoneId);
+            }
+        }
+        return Collections.unmodifiableList(timeZoneIds);
+    }
+
     /**
      * 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