PolyUtil decoding differences between JavaScript and Java

Diego Iturriaga :

I have multiple points corresponding to a route in PolyUtil encoding. I show this route in a web and in native android app, the issue is that in my web it is shown correctly but in my android app it displays a little different.

I logged both PolyUtil decodings and the points decoded are different. Using PolyUtil interactive site i get the correct route. I think the issue is with android library.

PolyUtil encoded points:

lvzsEhgvuI~c@HbJr@lJ`@|MrDfJlE~GxCdEvQ~IhCfDh@bIi@dGwB|D{GL{VqBqGcHcEeNGqGpGmHnQ

android points decoded:

-34.88199, -56.15223
-34.883770000000005, -56.152280000000005
-34.885600000000004, -56.15254
-34.88799, -56.152710000000006
-34.889790000000005, -56.15361000000001
-34.89123, -56.15464000000001
-34.89222, -56.15541
-34.893980000000006, -56.15841
-34.89482, -56.1591
-34.896440000000005, -56.159310000000005
-34.89775, -56.1591
-34.898700000000005, -56.158500000000004
-34.898770000000006, -56.15708000000001
-34.8982, -56.15326
-34.89674, -56.15189
-34.894310000000004, -56.15091
-34.89294, -56.150870000000005
-34.89143, -56.152240000000006
-34.891290000000005, -56.15520000000001

web points decoded:

-34.876070000000006,-56.152370000000005
-34.88199,-56.152420000000006
-34.883770000000005,-56.152680000000004
-34.885600000000004,-56.15285000000001
-34.88799,-56.15375
-34.889790000000005,-56.15478
-34.89123,-56.155550000000005
-34.89222,-56.158550000000005
-34.893980000000006,-56.159240000000004
-34.89482,-56.15945000000001
-34.896440000000005,-56.159240000000004
-34.89775,-56.158640000000005
-34.898700000000005,-56.15722
-34.898770000000006,-56.153400000000005
-34.8982,-56.15203
-34.89674,-56.151050000000005
-34.894310000000004,-56.15101000000001
-34.89294,-56.15238000000001
-34.89143,-56.15534

in my web i decode like this:

google.maps.geometry.encoding.decodePath(encoded_estimated_wp);

in android app i decode like this:

PolyUtil.decode(encoded_path);

How can i fix the android route? It is shown incorrectly.

Andrii Omelchenko :

The code like:

List <LatLng> pathPoints = PolyUtil.decode("lvzsEhgvuI~c@HbJr@lJ`@|MrDfJlE~GxCdEvQ~IhCfDh@bIi@dGwB|D{GL{VqBqGcHcEeNGqGpGmHnQ");
for (LatLng point : pathPoints) {
    Log.d(TAG, "" + point.latitude + "," + point.longitude);
}
PolylineOptions polylineOptions = new PolylineOptions()
        .addAll(pathPoints)
        .color(Color.RED)
        .width(20);

decode polyline

lvzsEhgvuI~c@HbJr@lJ`@|MrDfJlE~GxCdEvQ~IhCfDh@bIi@dGwB|D{GL{VqBqGcHcEeNGqGpGmHnQ

exactly as in your web (google.maps.geometry.encoding.decodePath(encoded_estimated_wp);) decode:

-34.876070000000006,-56.152370000000005
-34.88199,-56.152420000000006
-34.883770000000005,-56.152680000000004
-34.885600000000004,-56.15285000000001
-34.88799,-56.15375
-34.889790000000005,-56.15478
-34.89123,-56.155550000000005
-34.89222,-56.158550000000005
-34.893980000000006,-56.159240000000004
...

So check your android-maps-utils in app buld.gradle file dependences and add latest version (0.5+ for now):

dependencies {
    ...
    implementation 'com.google.maps.android:android-maps-utils:0.5+'
}

or use custom decodePoly() method like in this answer of Marlon (actually its grabbed from android-map-utils) and gives the same result:

private List<LatLng> decodePoly(String encoded) {

  List<LatLng> poly = new ArrayList<>();
  int index = 0, len = encoded.length();
  int lat = 0, lng = 0;

  while (index < len) {
      int b, shift = 0, result = 0;
      do {
          b = encoded.charAt(index++) - 63;
          result |= (b & 0x1f) << shift;
          shift += 5;
      } while (b >= 0x20);
      int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
      lat += dlat;

      shift = 0;
      result = 0;
      do {
          b = encoded.charAt(index++) - 63;
          result |= (b & 0x1f) << shift;
          shift += 5;
      } while (b >= 0x20);
      int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
      lng += dlng;

      LatLng p = new LatLng((((double) lat / 1E5)),
              (((double) lng / 1E5)));
      poly.add(p);
  }

  return poly;
}