Calculate the length of a polyline using Geolocator and a Google Maps Polyline

getLengthofPolyline.dart

Polyline track = new Polyline(polylineId: PolylineId("1"), points: [/*your track data*/]);
distance = 0;

for (int i = 0; i < track.points.length; i++) {
   if (track.points.length > 1 && i > 0) {
      LatLng startPoint = track.points[i - 1];
      LatLng endPoint = track.points[i];
      distance += Geolocator.distanceBetween(startPoint.latitude, startPoint.longitude, endPoint.latitude, endPoint.longitude);
   }
}
print(distance);