iPhone MKMapView - MKPolygon Issues

Question

I am trying to plot a MKPolygon on a MKMapView in iOS 4.0. I have an NSArray which contains custom objects that include properties for latitude/longitude. I have a code samp

Answer 1

The polygonWithCoordinates method wants a C array of CLLocationCoordinate2D structs. You can use malloc to allocate memory for the array (and free to release the memory). Loop through your NSArray and set it each element in the struct array.

For example:

coordsLen = [coordinateData count];
CLLocationCoordinate2D *coords = malloc(sizeof(CLLocationCoordinate2D) * coordsLen);
for (int i=0; i < coordsLen; i++)
{
    YourCustomObj *coordObj = (YourCustomObj *)[coordinateData objectAtIndex:i];
    coords[i] = CLLocationCoordinate2DMake(coordObj.latitude, coordObj.longitude);
}
MKPolygon *polygon = [MKPolygon polygonWithCoordinates:coords count:coordsLen];
free(coords);
[mapView addOverlay:polygon];

The viewForOverlay method should look like this:

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    MKPolygonView *polygonView = [[[MKPolygonView alloc] initWithPolygon:overlay] autorelease]; 
    polygonView.lineWidth = 1.0;
    polygonView.strokeColor = [UIColor redColor];
    polygonView.fillColor = [UIColor greenColor];
    return polygonView;
}

Answer 2

For iOS 7.0 and later we should use MKPolygonRenderer instead of MKPolygonView,

- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay
{
   MKPolygonRenderer * polygonView = [[MKPolygonRenderer alloc] initWithPolygon:overlay];
   polygonView.fillColor   = [UIColor greenColor];
   polygonView.strokeColor = [UIColor redColor] ;
   polygonView.lineWidth   = 1.0;
   return polygonView;
}

Answer 3

coordinatesArray; //Your array containing the coordinates

for (int i=0; i <[coordinatesArray count]; i++) 
{
   float latitude  = [coordinatesArray[i][@"latitude"] floatValue];
   float longitude  = [coordinatesArray[i][@"longitude"] floatValue];
   MKPolygon *polygon;
   CLLocationCoordinate2D coordinates[[coordinatesArray count]];
   coordinates[i] = CLLocationCoordinate2DMake(latitude , longitude);
   polygon = [MKPolygon polygonWithCoordinates:coordinates count:[coordinatesArray count]];
   [self.mapView addOverlay:polygon];
}

//Your "coordinatesArray" is an array containing the dictionary with multiple values of latitude and longitude keys. //Hope this helps you.

Answer 4

Code in Swift 4

For coordinates in json:

{
"coordinates": [
    [-73.947676,40.660297],
    [-73.947264,40.656437],
    [-73.947159,40.655594],
    [-73.946479,40.6491],
    [-73.947467,40.649039]
}

Read the coordinates:

let coordinates = json["coordinates"] as! [[Double]] 

Create points array:

var locationCoordinates = [CLLocationCoordinate2D]()    
for coordinate in coordinates{
   locationCoordinates.append(CLLocationCoordinate2DMake(coordinate.last!, coordinate.first!))
}

Create a polygon and add it to the map:

map.addOverlay(MKPolyline(coordinates: locationCoordinates, 
                                count: locationCoordinates.count))

Make sure your VC confronts to MKMapViewDelegate

class ViewController: UIViewController, MKMapViewDelegate { ... }

And add this method:

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    if overlay is MKPolygon {
        let polygonView = MKPolygonRenderer(overlay: overlay)
        polygonView.fillColor = .black
        polygonView.strokeColor = .red
        polygonView.lineWidth = 2.0

        return polygonView

    return MKOverlayRenderer()
}