Setting the zoom level for a MKMapView

Question

I have a map which shows correctly, the only thing I want to do now is set the zoom level when it loads. Is there a way to do this?

Thanks

Answer 1

I hope following code fragment would help you.

- (void)handleZoomOutAction:(id)sender {
    MKCoordinateRegion newRegion=MKCoordinateRegionMake(mapView.region.center,MKCoordinateSpanMake(mapView.region.s       pan.latitudeDelta/0.5, mapView.region.span.longitudeDelta/0.5));
    [mapView setRegion:newRegion];
}


- (void)handleZoomInAction:(id)sender {
    MKCoordinateRegion newRegion=MKCoordinateRegionMake(mapView.region.center,MKCoordinateSpanMake(mapView.region.span.latitudeDelta*0.5, mapView.region.span.longitudeDelta*0.5));
    [mapView setRegion:newRegion];
}

You can choose any value in stead of 0.5 to reduce or increase zoom level. I have used these methods on click of two buttons.

Answer 2

MKMapView extension based on this answer (+ floating-point zoom level accuracy):

import Foundation
import MapKit

extension MKMapView {
    var zoomLevel: Double {
        get {
            return log2(360 * (Double(self.frame.size.width / 256) / self.region.span.longitudeDelta)) + 1
        }

        set (newZoomLevel){
            setCenterCoordinate(coordinate:self.centerCoordinate, zoomLevel: newZoomLevel, animated: false)
        }
    }

    private func setCenterCoordinate(coordinate: CLLocationCoordinate2D, zoomLevel: Double, animated: Bool) {
        let span = MKCoordinateSpan(latitudeDelta: 0, longitudeDelta: 360 / pow(2, zoomLevel) * Double(self.frame.size.width) / 256)
        setRegion(MKCoordinateRegion(center: coordinate, span: span), animated: animated)
    }
}

Answer 3

Based on the fact that longitude lines are spaced apart equally at any point of the map, there is a very simple implementation to set the centerCoordinate and zoomLevel:

@interface MKMapView (ZoomLevel)

@property (assign, nonatomic) NSUInteger zoomLevel;

- (void)setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate
                  zoomLevel:(NSUInteger)zoomLevel
                   animated:(BOOL)animated;

@end


@implementation MKMapView (ZoomLevel)

- (void)setZoomLevel:(NSUInteger)zoomLevel {
    [self setCenterCoordinate:self.centerCoordinate zoomLevel:zoomLevel animated:NO];
}

- (NSUInteger)zoomLevel {
    return log2(360 * ((self.frame.size.width/256) / self.region.span.longitudeDelta)) + 1;
}

- (void)setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate
zoomLevel:(NSUInteger)zoomLevel animated:(BOOL)animated {
    MKCoordinateSpan span = MKCoordinateSpanMake(0, 360/pow(2, zoomLevel)*self.frame.size.width/256);
    [self setRegion:MKCoordinateRegionMake(centerCoordinate, span) animated:animated];
}

@end