Method getRouteBetweenCoordinates from Polylinepoints is unrecorgnized

Question

I am trying to get the distance between points for a pick-up and drop-off; however, every time use the method getRouteBetweenCoordinates I get the following error:

The method 'RouteBetweenCoordinatesRequest' isn't defined for the type '_HomeScreenState'.Try correcting the name to the name of an existing method, or defining a method named 'RouteBetweenCoordinatesRequest'.

Here is my code:

Future<void> _calculateRoute() async {
        if (_pickupLocation == null || _deliveryLocation == null) return;
    
        final polylinePoints = PolylinePoints();
        final request = RouteBetweenCoordinatesRequest(
          apiKey: 'YOUR_API_KEY',
          origin:
              PointLatLng(_pickupLocation!.latitude, _pickupLocation!.longitude),
          destination: PointLatLng(
              _deliveryLocation!.latitude, _deliveryLocation!.longitude),
        );
    
        final result =
            await polylinePoints.getRouteBetweenCoordinates(request: request);
    
        if (result.points.isNotEmpty) {
          final points = result.points
              .map((point) => LatLng(point.latitude, point.longitude))
              .toList();
    
          setState(() {
            _polylines = {
              Polyline(
                polylineId: const PolylineId('route'),
                points: points,
                color: Colors.blue,
                width: 4,
              )
            };
    
            _distance = _calculateDistanceBetween(
              _pickupLocation!.latitude,
              _pickupLocation!.longitude,
              _deliveryLocation!.latitude,
              _deliveryLocation!.longitude,
            );
            _totalCost = _distance * 15;
            _showRoute = true;
          });
        }
      }
    
      double _calculateDistanceBetween(
          double lat1, double lon1, double lat2, double lon2) {
        const double earthRadius = 6371;
        final double dLat = _degreesToRadians(lat2 - lat1);
        final double dLon = _degreesToRadians(lon2 - lon1);
        final double a = sin(dLat / 2) * sin(dLat / 2) +
            cos(_degreesToRadians(lat1)) *
                cos(_degreesToRadians(lat2)) *
                sin(dLon / 2) *
                sin(dLon / 2);
        final double c = 2 * atan2(sqrt(a), sqrt(1 - a));
        return earthRadius * c;
      }
    
      double _degreesToRadians(double degrees) => degrees * (pi / 180);
    
      void _confirmOrder() => Navigator.push(
            context,
            MaterialPageRoute(
              builder: (context) => PaymentScreen(
                distance: _distance,
                totalCost: _totalCost,
              ),
            ),
          );

Answer 1

Base on the error, it looks like you missed importing a file containing RouteBetweenCoordinatesRequest class but then, that's not the main issue. what you really want to do is instantiating the Polylinepoint class and then call getRouteBetweenCoordinates method of the class:

The correct version of your _calculateRoute code will likely be:

Future<void> _calculateRoute() async {
        if (_pickupLocation == null || _deliveryLocation == null) return;
    
        final polylinePoints = PolylinePoints();
        final request = polylinePoints.getRouteBetweenCoordinates( # Changes here
          apiKey: 'YOUR_API_KEY',
          origin:
              PointLatLng(_pickupLocation!.latitude, _pickupLocation!.longitude),
          destination: PointLatLng(
              _deliveryLocation!.latitude, _deliveryLocation!.longitude),
        );
    
        final result =
            await polylinePoints.getRouteBetweenCoordinates(request: request);
    
        if (result.points.isNotEmpty) {
          final points = result.points
              .map((point) => LatLng(point.latitude, point.longitude))
              .toList();
    
          setState(() {
            _polylines = {
              Polyline(
                polylineId: const PolylineId('route'),
                points: points,
                color: Colors.blue,
                width: 4,
              )
            };
    
            _distance = _calculateDistanceBetween(
              _pickupLocation!.latitude,
              _pickupLocation!.longitude,
              _deliveryLocation!.latitude,
              _deliveryLocation!.longitude,
            );
            _totalCost = _distance * 15;
            _showRoute = true;
          });
        }
      }