Using IBAction Buttons to Zoom MapView

Question

I have an issue. My current location is displayed and centered in a map view however the map region doesn\'t get zoomed in to. I tried taking Rob\'s advice by taking span an

Answer 1

You can get the current region, multiply or divide the span by two, as appropriate (dividing on zoom in, multiplying on zoom out), and then set the region:

- (IBAction)zoomIn:(id)sender {
    MKCoordinateRegion region = self.mapView.region;
    region.span.latitudeDelta /= 2.0;
    region.span.longitudeDelta /= 2.0;
    [self.mapView setRegion:region animated:YES];
}

- (IBAction)zoomOut:(id)sender {
    MKCoordinateRegion region = self.mapView.region;
    region.span.latitudeDelta  = MIN(region.span.latitudeDelta  * 2.0, 180.0);
    region.span.longitudeDelta = MIN(region.span.longitudeDelta * 2.0, 180.0);
    [self.mapView setRegion:region animated:YES];
}

---

If you want to have the map automatically zoom to your location, you can use:

self.mapView.userTrackingMode = MKUserTrackingModeFollow;

If you want to do this manually, you can do something like the following. First, define an class property for whether you've zoomed in already or not:

@property (nonatomic) BOOL alreadySetZoomScale;

then change your didUpdateLocations (or didUpdateToLocation) to check this and set the zoom scale once:

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
    CLLocation* newLocation = [locations lastObject]; // if less than zero, then valid lat and long not found

    if (newLocation.horizontalAccuracy < 0)
        return;

    if (!self.alreadySetZoomScale)
    {
        MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(newLocation.coordinate, 1609, 1609); // 1 mile = 1609.34 meters
        self.mapView.region = region;
        [self.mapView setRegion:region animated:YES];
        self.alreadySetZoomScale = YES;
    }
    else
    {
        [self.mapView setCenterCoordinate:newLocation.coordinate animated:YES];
    }
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    // if prior to iOS 6, use this old `MKMapViewDelegate` method, but call our
    // other routine.

    if (SYSTEM_VERSION_LESS_THAN(@"6.0"))
        [self locationManager:manager didUpdateLocations:@[newLocation]];
}

This basically says, "if I haven't zoomed in yet, set the region based upon the newLocation and a certain number of meters around that location, but if I have already done that, the just set the center coordinate based upon my current location, but don't change the zoom scale (in case I already zoomed in or out). This also does some conditional iOS version number logic (using the macros shown here), making sure if the end-user is running iOS prior to 6.0, that it will call our updated method.

By the way, if you're showing the user location on the map (e.g. self.mapView.showsUserLocation = YES;), you might want to have this didUpdateLocations also remove the overlay associated with the MKUserLocation before moving the map center, otherwise it can leave the old overlay sitting around:

[self.mapView removeOverlays:self.mapView.overlays];