问题
I have the swift code below that draws a polygon and drops an annotation on MKMapView. I am trying to figure out how i could identify if the annotation's coordinate is within the polygon?
import UIKit
import MapKit
class ViewController: UIViewController {
@IBOutlet weak var mapView: MKMapView!
override func viewDidLoad() {
super.viewDidLoad()
let initialLocation = CLLocation(latitude: 49.140838, longitude: -123.127886)
centerMapOnLocation(initialLocation)
addBoundry()
var annotation = MKPointAnnotation()
annotation.coordinate = point1
annotation.title = "Roatan"
annotation.subtitle = "Honduras"
mapView.addAnnotation(annotation)
}
var points = [CLLocationCoordinate2DMake(49.142677, -123.135139),
CLLocationCoordinate2DMake(49.142730, -123.125794),
CLLocationCoordinate2DMake(49.140874, -123.125805),
CLLocationCoordinate2DMake(49.140885, -123.135214)]
var point1 = CLLocationCoordinate2DMake(49.141821, -123.131577)
func addBoundry() {
let polygon = MKPolygon(coordinates: &points, count: points.count)
mapView.addOverlay(polygon)
}
let regionRadius: CLLocationDistance = 1000
func centerMapOnLocation(location: CLLocation) {
let coordinateRegion = MKCoordinateRegionMakeWithDistance(location.coordinate, regionRadius * 2.0, regionRadius * 2.0)
mapView.setRegion(coordinateRegion, animated: true)
}
func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {
if overlay is MKPolygon {
let polygonView = MKPolygonRenderer(overlay: overlay)
polygonView.strokeColor = UIColor.magentaColor()
return polygonView
}
return nil
}
}
回答1:
I created a Swift version of the answer by @StefanS and made it easier to read by porting the code from this answer
func isPoint(point: MKMapPoint, insidePolygon poly: MKPolygon) -> Bool {
let polygonVerticies = poly.points()
var isInsidePolygon = false
for i in 0..<poly.pointCount {
let vertex = polygonVerticies[i]
let nextVertex = polygonVerticies[(i + 1) % poly.pointCount]
// The vertices of the edge we are checking.
let xp0 = vertex.x
let yp0 = vertex.y
let xp1 = nextVertex.x
let yp1 = nextVertex.y
if ((yp0 <= point.y) && (yp1 > point.y) || (yp1 <= point.y) && (yp0 > point.y))
{
// If so, get the point where it crosses that line. This is a simple solution
// to a linear equation. Note that we can't get a division by zero here -
// if yp1 == yp0 then the above if be false.
let cross = (xp1 - xp0) * (point.y - yp0) / (yp1 - yp0) + xp0
// Finally check if it crosses to the left of our test point. You could equally
// do right and it should give the same result.
if cross < point.x {
isInsidePolygon = !isInsidePolygon
}
}
}
return isInsidePolygon
}
回答2:
- (BOOL)isPoint:(MKMapPoint)point insidePolygon:(MKPolygon *)poly {
MKMapPoint *a = poly.points;
BOOL isInsidePolygon = NO;
double testx = point.x;
double testy = point.y;
NSUInteger i = 0, j = 0, nvert = [poly pointCount];
for (i = 0, j = nvert - 1; i < nvert; j = i++) {
if (((a[i].y >= testy) != (a[j].y >= testy)) &&
(testx <= (a[j].x - a[i].x) * (testy - a[i].y) / (a[j].y - a[i].y) + a[i].x)) {
isInsidePolygon = !isInsidePolygon;
}
}
return isInsidePolygon;
}
Because the points x y are in Mercator projection coordinates, this makes sense and you don't need to convert to spherical coordinates for the calculation.
Why this is a correct calculation here.
EDIT: updated so that the calculation also considers a point on the line as inside the poly.
回答3:
How about using MkPolygon.intersect()? This requires converting the point to a tiny MKMapRect, but it is simpler and may get some acceleration from the underlying API:
func pointIsInside(point: MKMapPoint, polygon: MKPolygon) -> Bool {
let mapRect = MKMapRectMake(point.x, point.y, 0.0001, 0.0001)
return polygon.intersects(mapRect)
}
回答4:
You can create a polygon renderer object and check if it's path contains the point based on the location in the map:
func checkIf(_ location: CLLocationCoordinate2D, areInside polygon: MKPolygon) -> Bool {
let polygonRenderer = MKPolygonRenderer(polygon: polygon)
let mapPoint = MKMapPointForCoordinate(location)
let polygonPoint = polygonRenderer.point(for: mapPoint)
return polygonRenderer.path.contains(polygonPoint)
}
来源:https://stackoverflow.com/questions/31469835/mkpolygon-how-to-determine-if-a-cllocationcoordinate2d-is-in-a-cllocationcoord