Geppelt Geppelt - 2 years ago 151
iOS Question

Converting View Points to MKMapView Coordinates

My objective is to convert the top left and bottom right points of my view to lat/lon coordinates. These lat/lon coordinates will be used to query annotation locations that only exist within the view (not all 5000+).

I found this Objective-C tip on Stackoverflow. But the issue I have is that it is converting 0,0 from the mapView (a lat/lon of -180,-180. Aka, the Southpole).

So instead of:

topLeft = mapView.convertPoint(CGPointMake(0, 0), toCoordinateFromView: self.mapView)


I figured I could simply do:

topLeft = view.convertPoint(CGPointMake(0, 0), toCoordinateFromView: self.mapView)


But I get the error:


Cannot invoke 'convertPoint' with an argument list of type '(CGPoint,
toCoordinateFromView: MKMapView!)'


I have spent a day trying to figure it out, but to no avail, and I have come to you seeking guidance. Any help would be much appreciated.

Here is the complete function:

func findCornerLocations(){

var topLeft = CLLocationCoordinate2D()
let mapView = MKMapView()
topLeft = view.convertPoint(CGPointMake(0, 0), toCoordinateFromView: self.mapView)

print(topLeft.latitude, topLeft.longitude)
}

Answer Source

You were very, very close!

let topLeft = map.convertPoint(CGPointMake(0, 0), toCoordinateFromView: self.view)
let bottomleft = map.convertPoint(CGPointMake(0, self.view.frame.size.height), toCoordinateFromView: self.view)

When implemented, it'll look like this:

        let map = MKMapView()
        map.frame = CGRectMake(100, 100, 100, 100)
        let coord = CLLocationCoordinate2DMake(37, -122)
        let span = MKCoordinateSpanMake(1, 1)
        map.region = MKCoordinateRegionMake(coord, span)
        self.view.addSubview(map)

        let topleft = map.convertPoint(CGPointMake(0, 0), toCoordinateFromView: self.view)
        let bottomleft = map.convertPoint(CGPointMake(0, self.view.frame.size.height), toCoordinateFromView: self.view)

        print("top left = \(topleft)")
        print("bottom left = \(bottomleft)")
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