How to limit MKMapView Maximum zoom level with Swift

Question

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

What problems are you facing converting it to swift? can you please mention about it. — Bhavin Kansagara, Dec 26 '18 at 15:11
There need to be an interface MKMapView+ZoomLevel. But, I could not get this in swift. — tejasree vangapalli, Dec 26 '18 at 15:37
A solution to your problem https://stackoverflow.com/a/42534563/656600 — rptwsthi, Mar 20 '19 at 07:37

score 1 · Answer 1 · answered Dec 26 '18 at 15:55

1

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.

answered Dec 26 '18 at 15:55

Eskils

126
8

This is exactly how I did it. I should note that changing that value also changes the zoom, so you'll need a flag, to prevent excessive actions (I do a lot, in my region change callback). – Chris Marshall Jul 28 '23 at 19:47

score 1 · Answer 2 · answered Dec 26 '18 at 16:00

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)
  }
}

This function is part of the `CLLocationManagerDelegate` protocol, you should implement it in the controller where you are using the user location, it is called automatically as the user updates his location, but this is just an example, you can use the `zoom` method on your mapView where ever suits you right. — Arie Pinto, Dec 26 '18 at 16:17

How to limit MKMapView Maximum zoom level with Swift

2 Answers2