google maps flutter check if a point inside a polygon

I found this answer and just modified some minor things to work with dart, I ran a test on a hardcoded polygon. The list _area is my polygon and _polygons is required for my mapcontroller.

final Set<Polygon> _polygons = {};List<LatLng> _area = [LatLng(-17.770992200, -63.207739700),LatLng(-17.776386600, -63.213576200),LatLng(-17.778348200, -63.213576200),LatLng(-17.786848100, -63.214262900),LatLng(-17.798289700, -63.211001300),LatLng(-17.810547700, -63.200701600),LatLng(-17.815450600, -63.185252100),LatLng(-17.816267800, -63.170660900),LatLng(-17.800741300, -63.153838100),LatLng(-17.785867400, -63.150919800),LatLng(-17.770501800, -63.152636400),LatLng(-17.759712400, -63.160361200),LatLng(-17.755952300, -63.169802600),LatLng(-17.752519100, -63.186625400),LatLng(-17.758404500, -63.195551800),LatLng(-17.770992200, -63.206538100),LatLng(-17.770996000, -63.207762500)];

The function ended like this:

bool _checkIfValidMarker(LatLng tap, List<LatLng> vertices) {    int intersectCount = 0;    for (int j = 0; j < vertices.length - 1; j++) {      if (rayCastIntersect(tap, vertices[j], vertices[j + 1])) {        intersectCount++;      }    }    return ((intersectCount % 2) == 1); // odd = inside, even = outside;  }  bool rayCastIntersect(LatLng tap, LatLng vertA, LatLng vertB) {    double aY = vertA.latitude;    double bY = vertB.latitude;    double aX = vertA.longitude;    double bX = vertB.longitude;    double pY = tap.latitude;    double pX = tap.longitude;    if ((aY > pY && bY > pY) || (aY < pY && bY < pY) || (aX < pX && bX < pX)) {      return false; // a and b can't both be above or below pt.y, and a or      // b must be east of pt.x    }    double m = (aY - bY) / (aX - bX); // Rise over run    double bee = (-aX) * m + aY; // y = mx + b    double x = (pY - bee) / m; // algebra is neat!    return x > pX;  }

Notice the polygons property and the onTap method. I was trying to check if the marker created in my map was inside my polygon:

GoogleMap(                          initialCameraPosition: CameraPosition(                            target: target, //LatLng(0, 0),                            zoom: 16,                          ),                          zoomGesturesEnabled: true,                          markers: markers,                          polygons: _polygons,                          onMapCreated: (controller) =>                              _mapController = controller,                          onTap: (latLng) {                            _getAddress(latLng);                          },                        )

Then i just used the following call in my _getAddress method:

_checkIfValidMarker(latLng, _area);

I hope it helps you to create what you need.

The easiest way to use it - https://pub.dev/packages/maps_toolkit

with isLocationOnPath method.