CODEWITHSUNDEEP
iosswift
tejasree vangapalli
tejasree vangapalli

Reputation: 89

How to limit MKMapView Maximum zoom level with Swift

I am trying to limit maximum zoom level in my swift application without which my app is crashing with memory overload during zooming. I am following the suggestions present in Is there way to limit MKMapView maximum zoom level? One of the suggestion is to implement regionDidChangeAnimated with following code in Objective-C. Following is the code

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated
{
    // Constrain zoom level to 8.
    if( [mapView zoomLevel] < 8 )
    {
        [mapView setCenterCoordinate:mapView.centerCoordinate 
            zoomLevel:8 
            animated:NO];
    }
}

I am trying to convert it into Swift and facing problems. How do I convert into swift

Upvotes: 2

Views: 1898

Answers (2)

Arie Pinto
Arie Pinto

Reputation: 1292

I have a swift version of what you looking for, i can't remember where i got it from but i shouldn't be credited for it.

extension MKMapView {
var MERCATOR_OFFSET : Double {
    return 268435456.0
}

var MERCATOR_RADIUS : Double  {
    return 85445659.44705395
}

private func longitudeToPixelSpaceX(longitude: Double) -> Double {
    return round(MERCATOR_OFFSET + MERCATOR_RADIUS * longitude * Double.pi / 180.0)
}

private func latitudeToPixelSpaceY(latitude: Double) -> Double {
    return round(MERCATOR_OFFSET - MERCATOR_RADIUS * log((1 + sin(latitude * Double.pi / 180.0)) / (1 - sin(latitude * Double.pi / 180.0))) / 2.0)
}

private  func pixelSpaceXToLongitude(pixelX: Double) -> Double {
    return ((round(pixelX) - MERCATOR_OFFSET) / MERCATOR_RADIUS) * 180.0 / Double.pi;
}

private func pixelSpaceYToLatitude(pixelY: Double) -> Double {
    return (Double.pi / 2.0 - 2.0 * atan(exp((round(pixelY) - MERCATOR_OFFSET) / MERCATOR_RADIUS))) * 180.0 / Double.pi;
}

private func coordinateSpan(withMapView mapView: MKMapView, centerCoordinate: CLLocationCoordinate2D, zoomLevel: UInt) ->MKCoordinateSpan {
    let centerPixelX = longitudeToPixelSpaceX(longitude: centerCoordinate.longitude)
    let centerPixelY = latitudeToPixelSpaceY(latitude: centerCoordinate.latitude)

    let zoomExponent = Double(20 - zoomLevel)
    let zoomScale = pow(2.0, zoomExponent)

    let mapSizeInPixels = mapView.bounds.size
    let scaledMapWidth =  Double(mapSizeInPixels.width) * zoomScale
    let scaledMapHeight = Double(mapSizeInPixels.height) * zoomScale

    let topLeftPixelX = centerPixelX - (scaledMapWidth / 2);
    let topLeftPixelY = centerPixelY - (scaledMapHeight / 2);

    //find delta between left and right longitudes
    let minLng = pixelSpaceXToLongitude(pixelX: topLeftPixelX)
    let maxLng = pixelSpaceXToLongitude(pixelX: topLeftPixelX + scaledMapWidth)
    let longitudeDelta = maxLng - minLng;

    let minLat = pixelSpaceYToLatitude(pixelY: topLeftPixelY)
    let maxLat = pixelSpaceYToLatitude(pixelY: topLeftPixelY + scaledMapHeight)
    let latitudeDelta = -1 * (maxLat - minLat);

    let span = MKCoordinateSpanMake(latitudeDelta, longitudeDelta)
    return span
}

func zoom(toCenterCoordinate centerCoordinate:CLLocationCoordinate2D ,zoomLevel: UInt) {
    let zoomLevel = min(zoomLevel, 20)
    let span = self.coordinateSpan(withMapView: self, centerCoordinate: centerCoordinate, zoomLevel: zoomLevel)
    let region = MKCoordinateRegionMake(centerCoordinate, span)
    self.setRegion(region, animated: true)

  }
}

Usage example:

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
if let location = manager.location?.coordinate {
   mapView.zoom(toCenterCoordinate: CLLocationCoordinate2D(latitude: location.latitude, longitude: location.longitude), zoomLevel: 16)
  }
}

Upvotes: 1

Eskils
Eskils

Reputation: 126

I think you can use mapView.camera.altitude instead.

So it will be like:

func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
    if mapView.camera.altitude < 8 {
        mapView.camera.altitude = 8
    }
}

Also remember that you will have to add MKMapViewDelegate as a superclass (class ViewController : UIViewController, MKMapViewDelegate)

Good luck!

Best Regards Eskils.

Upvotes: 1

Related Questions