Bugfix: prevent race condition in TrackPointCreator.

This race condition leads to a crash in TrackStatisticsUpdater as the time might appear to move backwards if the created TrackPoints are not stored in order. Might happen if multiple sensors (BLE or GPS) are used in simultaneously.

Every method affected by a race condition is now synchronized.

Problem was introduced in c4b8082efc

Fixes #1151.

src/main/java/de/dennisguse/opentracks/services/handlers/GPSHandler.java

@@ -12,6 +12,7 @@ import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
 
 import java.time.Duration;
+import java.time.Instant;
 
 import de.dennisguse.opentracks.R;
 import de.dennisguse.opentracks.data.models.Distance;
@@ -109,25 +110,23 @@ public class GPSHandler implements LocationListener, GpsStatus.GpsStatusListener
             return;
         }
 
-        TrackPoint trackPoint = new TrackPoint(location, trackPointCreator.createNow());
-        boolean isAccurate = trackPoint.fulfillsAccuracy(thresholdHorizontalAccuracy);
-        boolean isValid = LocationUtils.isValidLocation(location);
-
         if (gpsStatus != null) {
+            // Send each update to the status; please note that this TrackPoint is not stored.
+            TrackPoint trackPoint = new TrackPoint(location, Instant.ofEpochMilli(location.getTime()));
             gpsStatus.onLocationChanged(trackPoint);
         }
 
-        if (!isValid) {
+        if (!LocationUtils.isValidLocation(location)) {
             Log.w(TAG, "Ignore newTrackPoint. location is invalid.");
             return;
         }
 
-        if (!isAccurate) {
+        if (!LocationUtils.fulfillsAccuracy(location, thresholdHorizontalAccuracy)) {
             Log.d(TAG, "Ignore newTrackPoint. Poor accuracy.");
             return;
         }
 
-        trackPointCreator.onNewTrackPoint(trackPoint);
+        trackPointCreator.onChange(location);
     }
 
     @Override