Update to #71 - Better support for NMEA DOP parsing

* See #71 (comment) for details
* Add support for $GPGSA NMEA sentences
* Support parsing VDOP when the checksum appears next to that value without a comma separator
* Catch NumberFormatException and output error message to console in case there are other issues parsing DOP from NMEA
* Add more tests parsing DOP from GSA sentences

GPSTest/src/main/java/com/android/gpstest/GpsStatusFragment.java

@@ -290,7 +290,7 @@ public void onNmeaMessage(String message, long timestamp) {
                 mAltitudeMslView.setText(getString(R.string.gps_altitude_msl_value, altitudeMsl));
             }
         }
-        if (message.startsWith("$GNGSA")) {
+        if (message.startsWith("$GNGSA") || message.startsWith("$GPGSA")) {
             DilutionOfPrecision dop = GpsTestUtil.getDop(message);
             if (dop != null && mNavigating) {
                 showDopViews();

GPSTest/src/main/java/com/android/gpstest/util/GpsTestUtil.java

@@ -223,16 +223,17 @@ public static Double getAltitudeMeanSeaLevel(String nmeaSentence) {
     }
 
     /**
-     * Given a $GPGSA NMEA sentence, return the dilution of precision, or null if dilution of
+     * Given a $GNGSA or $GPGSA NMEA sentence, return the dilution of precision, or null if dilution of
      * precision can't be parsed.
      *
      * Example inputs are:
-     * $GNGSA,A,2,67,68,69,79,84,,,,,,,,1.3,1.0,0.8,2*3A
+     * $GPGSA,A,3,03,14,16,22,23,26,,,,,,,3.6,1.8,3.1*38
+     * $GNGSA,A,3,03,14,16,22,23,26,,,,,,,3.6,1.8,3.1,1*3B
      *
-     * Example outputs would be:
-     * PDOP is 1.3, HDOP is 1.0, and VDOP is 0.8
+     * Example output is:
+     * PDOP is 3.6, HDOP is 1.8, and VDOP is 3.1
      *
-     * @param nmeaSentence a $GNGSA NMEA sentence
+     * @param nmeaSentence a $GNGSA or $GPGSA NMEA sentence
      * @return the dilution of precision, or null if dilution of precision can't be parsed
      */
     public static DilutionOfPrecision getDop(String nmeaSentence) {
@@ -241,15 +242,28 @@ public static DilutionOfPrecision getDop(String nmeaSentence) {
         final int VDOP_INDEX = 17;
         String[] tokens = nmeaSentence.split(",");
 
-        if (nmeaSentence.startsWith("$GNGSA")) {
+        if (nmeaSentence.startsWith("$GNGSA") || nmeaSentence.startsWith("$GPGSA")) {
             String pdop = tokens[PDOP_INDEX];
             String hdop = tokens[HDOP_INDEX];
             String vdop = tokens[VDOP_INDEX];
+
+            // See https://github.com/barbeau/gpstest/issues/71#issuecomment-263169174
+            if (vdop.contains("*")) {
+                vdop = vdop.split("\\*")[0];
+            }
+
             if (!TextUtils.isEmpty(pdop) && !TextUtils.isEmpty(hdop) && !TextUtils.isEmpty(vdop)) {
-                return new DilutionOfPrecision(Double.valueOf(pdop), Double.valueOf(hdop),
-                        Double.valueOf(vdop));
+                DilutionOfPrecision dop = null;
+                try {
+                    dop = new DilutionOfPrecision(Double.valueOf(pdop), Double.valueOf(hdop),
+                            Double.valueOf(vdop));
+                } catch (NumberFormatException e) {
+                    // See https://github.com/barbeau/gpstest/issues/71#issuecomment-263169174
+                    Log.e(TAG, "Invalid DOP values in NMEA: " + nmeaSentence);
+                }
+                return dop;
             } else {
-                Log.w(TAG, "Couldn't parse DOP from NMEA: " + nmeaSentence);
+                Log.w(TAG, "Empty DOP values in NMEA: " + nmeaSentence);
                 return null;
             }
         } else {

GPSTest/src/test/java/com/android/gpstest/GpsTestUtilTest.java

@@ -47,12 +47,55 @@ public void testGetAltitudeFromNmea() {
     @Test
     public void testGetDopFromNmea() {
         DilutionOfPrecision dop;
-        final String sentence = "$GNGSA,A,2,67,68,69,79,84,,,,,,,,1.3,1.0,0.8,2*3A";
 
-        dop = GpsTestUtil.getDop(sentence);
+        // LG G5 w/ Android 6.0.1
+        final String s1 = "$GNGSA,A,2,67,68,69,79,84,,,,,,,,1.3,1.0,0.8,2*3A";
+
+        // LG G5 w/ Android 7.0
+        final String s2 = "$GPGSA,A,3,03,14,16,22,23,26,,,,,,,3.6,1.8,3.1*38";
+        final String s3 = "$GNGSA,A,3,03,14,16,22,23,26,,,,,,,3.6,1.8,3.1,1*3B";
+
+        // From http://aprs.gids.nl/nmea/#gsa
+        final String s4 = "$GPGSA,A,3,,,,,,16,18,,22,24,,,3.6,2.1,2.2*3C";
+        final String s5 = "$GPGSA,A,3,19,28,14,18,27,22,31,39,,,,,1.7,1.0,1.3*35";
+
+        // From http://www.gpsinformation.org/dale/nmea.htm#GSA
+        final String s6 = "$GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39";
+
+        dop = GpsTestUtil.getDop(s1);
 
         assertEquals(1.3d, dop.getPositionDop());
         assertEquals(1.0d, dop.getHorizontalDop());
         assertEquals(0.8d, dop.getVerticalDop());
+
+        dop = GpsTestUtil.getDop(s2);
+
+        assertEquals(3.6d, dop.getPositionDop());
+        assertEquals(1.8d, dop.getHorizontalDop());
+        assertEquals(3.1d, dop.getVerticalDop());
+
+        dop = GpsTestUtil.getDop(s3);
+
+        assertEquals(3.6d, dop.getPositionDop());
+        assertEquals(1.8d, dop.getHorizontalDop());
+        assertEquals(3.1d, dop.getVerticalDop());
+
+        dop = GpsTestUtil.getDop(s4);
+
+        assertEquals(3.6d, dop.getPositionDop());
+        assertEquals(2.1d, dop.getHorizontalDop());
+        assertEquals(2.2d, dop.getVerticalDop());
+
+        dop = GpsTestUtil.getDop(s5);
+
+        assertEquals(1.7d, dop.getPositionDop());
+        assertEquals(1.0d, dop.getHorizontalDop());
+        assertEquals(1.3d, dop.getVerticalDop());
+
+        dop = GpsTestUtil.getDop(s6);
+
+        assertEquals(2.5d, dop.getPositionDop());
+        assertEquals(1.3d, dop.getHorizontalDop());
+        assertEquals(2.1d, dop.getVerticalDop());
     }
 }