NativeScript/Android: drawing polyline for Google Directions API response on Google Map

sample.js

const debug = require('nativescript-debug')(__filename);

const application = require('application');
const observable = require('data/observable');

const LatLng = com.google.android.gms.maps.model.LatLng;
const PolylineOptions = com.google.android.gms.maps.model.PolylineOptions;
const LatLngBounds = com.google.android.gms.maps.model.LatLngBounds;
const CameraUpdateFactory = com.google.android.gms.maps.CameraUpdateFactory;

const polyline = require('polyline');


var model = new observable.Observable();
model.set('constloading', false);
model.set('directionsShown', false);


var directionsPolyline;

function clearDirections(args) {
  debug('clearDirections');
  if (directionsPolyline) {
    directionsPolyline.remove();
    model.set('directionsShown', false);
  }
}
exports.clearDirections = clearDirections;

function drawDirections(args) {
  debug('drawDirections');

  clearDirections();

  model.set('loading', true);
  fetch('https://maps.googleapis.com/maps/api/directions/json', {
      query: {
        origin: 'somewhere ...',
        destination: 'somewhere else ...',
        mode: 'driving',
        key: 'your google service key here',
      },
    }).then(function(result) {
      debug('drawDirections', result);
      var route = result.routes[0];
      var polylineData = polyline.decode(route.overview_polyline.points);
      debug('drawDirections', route.overview_polyline.points, polylineData);
      if (application.android) {
        var polylineOptions = new PolylineOptions();
        polylineOptions.width(8);
        polylineOptions.geodesic(true);
        polylineOptions.color(CONST.ROUTE_COLOR.android);
        polylineData.forEach(function(latlng) {
          polylineOptions.add(new LatLng(latlng[0], latlng[1]));
        });
        directionsPolyline = mapView.gMap.addPolyline(polylineOptions);
        var bounds = new LatLngBounds.Builder();
        bounds.include(new LatLng(route.bounds.northeast.lat, route.bounds.northeast.lng));
        bounds.include(new LatLng(route.bounds.southwest.lat, route.bounds.southwest.lng));
        mapView.gMap.animateCamera(CameraUpdateFactory.newLatLngBounds(bounds.build(), 50));
        model.set('directionsShown', true);
      } else {
        // TODO: iOS
      }
    })
    .catch(function(error) {
      debug('drawDirections', error);
      snackbar.simple("Échec d'opération");
    }).finally(function() {
      model.set('loading', false);
    });

}
exports.drawDirections = drawDirections;