Fix UI flicker problem and update wordings

- "Set time zone automatically" changes to "Set automatically".
- "Use location to set time zone" changes to "Use location"
- Add a new summary text with "Location may be used to set time zone".

Fixes: 233968737
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.datetime
Change-Id: Ia16c428e906cda4ebe052bad83c3f574075a7a64

res/values/strings.xml

@@ -606,7 +606,7 @@
     <!-- Date & time setting screen setting switch title: whether the system clock (Unix epoch time) should be determined automatically [CHAR LIMIT=100] -->
     <string name="date_time_auto">Set time automatically</string>
     <!-- Date & time setting screen setting switch title: whether the time zone should be determined automatically [CHAR LIMIT=100]  -->
-    <string name="zone_auto_title">Set time zone automatically</string>
+    <string name="zone_auto_title">Set automatically</string>
     <!-- Date & time setting screen setting option summary text for the automatic 24 hour setting checkbox [CHAR LIMIT=100] -->
     <string name="date_time_24hour_auto">Use locale default</string>
     <!-- Date & time setting screen setting check box title [CHAR LIMIT=30] -->
@@ -4254,7 +4254,7 @@
     <string name="managed_profile_location_services">Location services for work</string>
 
     <!-- [CHAR LIMIT=60] Date&Time settings screen, toggle button title -->
-    <string name="location_time_zone_detection_toggle_title">Use location to set time zone</string>
+    <string name="location_time_zone_detection_toggle_title">Use location</string>
     <!-- [CHAR LIMIT=60] Date&Time settings screen, title of the dialog shown when user tries to
          enable GeoTZ when Location toggle is off. -->
     <string name="location_time_zone_detection_location_is_off_dialog_title">Device location needed</string>
@@ -4280,6 +4280,8 @@
     <!-- [CHAR LIMIT=NONE] Location settings screen, summary when location time zone detection is not
          allowed for the user, e.g. because of device policy -->
     <string name="location_time_zone_detection_not_allowed">Location time zone detection changes are not allowed</string>
+    <!-- [CHAR LIMIT=NONE] Location settings screen, summary when location time zone detection is enabled. -->
+    <string name="location_time_zone_detection_auto_is_on">Location may be used to set time zone</string>
 
     <!-- [CHAR LIMIT=30] Security & location settings screen, setting check box label for Google location service (cell ID, wifi, etc.) -->
     <string name="location_network_based">Wi\u2011Fi &amp; mobile network location</string>

res/xml/date_time_prefs.xml

@@ -45,7 +45,6 @@
         <com.android.settingslib.RestrictedSwitchPreference
             android:key="auto_zone"
             android:title="@string/zone_auto_title"
-            settings:allowDividerAbove="true"
             settings:userRestriction="no_config_date_time"/>
 
         <!-- This preference gets removed if location-based time zone detection is not supported -->

src/com/android/settings/datetime/LocationTimeZoneDetectionPreferenceController.java

@@ -174,7 +174,7 @@ public class LocationTimeZoneDetectionPreferenceController
             // If capability is possessed, toggle status already tells all the information needed.
             // Returning null will make previous text stick on toggling.
             // See AbstractPreferenceController#refreshSummary.
-            return "";
+            summaryResId = R.string.location_time_zone_detection_auto_is_on;
         } else {
             // This is unexpected: getAvailabilityStatus() should ensure that the UI element isn't
             // even shown for known cases, or the capability is unknown.

tests/robotests/src/com/android/settings/datetime/LocationTimeZoneDetectionPreferenceControllerTest.java

@@ -150,7 +150,8 @@ public class LocationTimeZoneDetectionPreferenceControllerTest {
                 new TimeZoneCapabilitiesAndConfig(capabilities, configuration);
 
         when(mTimeManager.getTimeZoneCapabilitiesAndConfig()).thenReturn(capabilitiesAndConfig);
-        assertThat(mController.getSummary().toString()).isEmpty();
+        assertThat(mController.getSummary()).isEqualTo(
+                mContext.getString(R.string.location_time_zone_detection_auto_is_on));
     }
 
     @Test