diff --git a/mobile/src/com/cradle/iitc_mobile/IITC_UserLocation.java b/mobile/src/com/cradle/iitc_mobile/IITC_UserLocation.java index 551ee404..da47e1e6 100644 --- a/mobile/src/com/cradle/iitc_mobile/IITC_UserLocation.java +++ b/mobile/src/com/cradle/iitc_mobile/IITC_UserLocation.java @@ -136,6 +136,65 @@ public class IITC_UserLocation implements LocationListener, SensorEventListener mIitc.invalidateOptionsMenu(); } + private static final int TWO_MINUTES = 1000 * 60 * 2; + + /** + * Determines whether one Location reading is better than the current Location fix + * @param location The new Location that you want to evaluate + * @param currentBestLocation The current Location fix, to which you want to compare the new one + * + * code copied from http://developer.android.com/guide/topics/location/strategies.html#BestEstimate + */ + protected boolean isBetterLocation(Location location, Location currentBestLocation) { + if (currentBestLocation == null) { + // A new location is always better than no location + return true; + } + + // Check whether the new location fix is newer or older + long timeDelta = location.getTime() - currentBestLocation.getTime(); + boolean isSignificantlyNewer = timeDelta > TWO_MINUTES; + boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES; + boolean isNewer = timeDelta > 0; + + // If it's been more than two minutes since the current location, use the new location + // because the user has likely moved + if (isSignificantlyNewer) { + return true; + // If the new location is more than two minutes older, it must be worse + } else if (isSignificantlyOlder) { + return false; + } + + // Check whether the new location fix is more or less accurate + int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy()); + boolean isLessAccurate = accuracyDelta > 0; + boolean isMoreAccurate = accuracyDelta < 0; + boolean isSignificantlyLessAccurate = accuracyDelta > 100; + + // Check if the old and new location are from the same provider + boolean isFromSameProvider = isSameProvider(location.getProvider(), + currentBestLocation.getProvider()); + + // Determine location quality using a combination of timeliness and accuracy + if (isMoreAccurate) { + return true; + } else if (isNewer && !isLessAccurate) { + return true; + } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) { + return true; + } + return false; + } + + // Checks whether two providers are the same + private boolean isSameProvider(String provider1, String provider2) { + if (provider1 == null) { + return provider2 == null; + } + return provider1.equals(provider2); + } + /** * set the location mode to use. Available modes: * 0: don't show user's position @@ -157,10 +216,9 @@ public class IITC_UserLocation implements LocationListener, SensorEventListener @Override public void onLocationChanged(Location location) { - mLastLocation = location; + if (!isBetterLocation(location, mLastLocation)) return; - // throw away all positions with accuracy > 100 meters should avoid gps glitches - if (location.getAccuracy() > 100) return; + mLastLocation = location; // do not touch the javascript while iitc boots if (mIitc.isLoading()) return;