commit 2eeeec248a38ff33999c83f4b8d5bab7d50e79d2
author Nick Pelly <npelly@google.com> Wed Jul 18 13:13:37 2012 -0700
committer Nick Pelly <npelly@google.com> Fri Jul 20 10:07:07 2012 -0700
tree 2886aaefdd09bbafa7853dbbbb29aa866846045f
parent b8acd060d409f0e81ab3510b429cb86d3f34adb8

Improve Location object.

Add getElapsedRealtimeNano():

Currently Location just has getTime() and setTime() based on UTC time.
This is entirely unreliable since it is not guaranteed monotonic.
There is a lot of code that compares fix age based on deltas -
and it is all broken in the case of a system clock change. System
clock can change when switching cellular networks (and in some
cases when switching towers).

Document the meaning of getAccuracy():
It is the horizontal, 95% confidence radius.

Make some fields mandatory if they are reported by a LocationProvider:

All Locations returned by a LocationProvider must include at the
minimum a lat, long, timestamps, and accuracy. This is necessary
to perform fused location. There are no public API's for applications
to feed locations into a location provider so this should not cause
any breakage.

If a LocationProvider does not fill in enough fields on a Location
object then it is dropped, and logged.

Bug: 4305998
Change-Id: I7df77125d8a64e174d7bc8c2708661b4f33461ea

services/java/com/android/server/UiModeManagerService.java

diff --git a/services/java/com/android/server/UiModeManagerService.java b/services/java/com/android/server/UiModeManagerService.java
index d1f92a7..5299b71 100644
--- a/services/java/com/android/server/UiModeManagerService.java
+++ b/services/java/com/android/server/UiModeManagerService.java
@@ -308,7 +308,7 @@
             /* if new location is older than the current one, the devices hasn't
              * moved.
              */
-            if (location.getTime() < mLocation.getTime()) {
+            if (location.getElapsedRealtimeNano() < mLocation.getElapsedRealtimeNano()) {
                 return false;
             }
 
@@ -764,7 +764,8 @@
                         mLocationManager.getLastKnownLocation(providers.next());
                 // pick the most recent location
                 if (location == null || (lastKnownLocation != null &&
-                        location.getTime() < lastKnownLocation.getTime())) {
+                        location.getElapsedRealtimeNano() <
+                        lastKnownLocation.getElapsedRealtimeNano())) {
                     location = lastKnownLocation;
                 }
             }
@@ -781,6 +782,7 @@
                 location.setLatitude(0);
                 location.setAccuracy(417000.0f);
                 location.setTime(System.currentTimeMillis());
+                location.setElapsedRealtimeNano(SystemClock.elapsedRealtimeNano());
             }
             synchronized (mLock) {
                 mLocation = location;