Zoom in on user location in iOS - ios

Question

I've been trying to solve this for a few hours and I can't seem to arrive at a solution. I am trying to create a button on my map view that zooms in on the users location when pressed. Here is the code for the function that pertains to the button:
func zoomInOnLocation() {
let userLocation = MKUserLocation()
let locationManager = CLLocationManager()
locationManager.requestWhenInUseAuthorization()
let currentLocation: CLLocation? = userLocation.location
let latitude = currentLocation?.coordinate.latitude
let longitude = currentLocation?.coordinate.longitude
let span: MKCoordinateSpan = MKCoordinateSpan(latitudeDelta: 0.05, longitudeDelta: 0.05)
let location: CLLocationCoordinate2D = CLLocationCoordinate2DMake(latitude!, longitude!)
let region: MKCoordinateRegion = MKCoordinateRegionMake(location, span)
mapView.setRegion(region, animated: true)
}
When I click the button in the simulator, I receive an error stating fatal error:
unexpectedly found nil while unwrapping an Optional value
with the fifth line mapDelegate.mapView!... highlighted in red. Also, I added the proper tag to Info.plist. Any help is much appreciated.

Answer 1

Check this :
if #available(iOS 9.0, *) {
locationManager.requestLocation()
} else {
// Fallback
}
let latitude:CLLocationDegrees = //insert latitutde
let longitude:CLLocationDegrees = //insert longitude
let latDelta:CLLocationDegrees = 0.05
let lonDelta:CLLocationDegrees = 0.05
let span = MKCoordinateSpanMake(latDelta, lonDelta)
let location = CLLocationCoordinate2DMake(latitude, longitude)
let region = MKCoordinateRegionMake(location, span)
mapView.setRegion(region, animated: false)
For more : Making the map zoom to user location and annotation (swift 2)

Answer 2

So you probably do not want to to interact with the mapView delegate as you are doing right now.
How about adding the delegates to the class of the view that holds the mapView, like this:
class ViewController: UIViewController, CLLocationManagerDelegate, MKMapViewDelegate {
and setting the delegates in viewDidLoad():
override func viewDidLoad() {
super.viewDidLoad()
locationManager.delegate = self
mapView.delegate = self
}
And of course you want to have the locationManager and userLocation set up:
let locationManager = CLLocationManager()
var userLocation = CLLocation()
Notice that userLocation is a variable because most likely you would want to update it at some point.
This is how you probably want to work with locationManager:
locationManager.desiredAccuracy = kCLLocationAccuracyBest
locationManager.requestWhenInUseAuthorization()
locationManager.startUpdatingLocation()
You would make changes according to the needs of your app, and taking into account that the desired accuracy has an impact on battery life. Also, are you starting and stopping updates on userLocation? Because I do not see that in your code, unless you are doing it outside of this function.
A good practice is to try to minimize what an specific function does down to one task. You probably want to do all this setup elsewhere and then only zoom in inside the function. :)
Finally, in order to zoom in, you can change the values of MKCoordinateSpanMake, and remember that larger span values zoom in the map, so a smaller area is viewable.
let userLocationCoordinates = CLLocationCoordinate2D(latitude: userLocation.coordinate.latitude, longitude: userLocation.coordinate.longitude)
let span = MKCoordinateSpanMake(0.3, 0.3)
let region = MKCoordinateRegion(center: userLocationCoordinates, span: span)
mapView.setRegion(region, animated: true)
Hopefully that helps you out a bit, let me know how it goes!

Answer 3

Perhaps this will help. I created this function to zoom into an area defined by an array of positions, ranging from just the current user location out to the area around a set of points making up a polyline. The function provides for a buffer around the points based on a regionPaddingFactor constant set in my system constants.
func setRectView(_ locations: [MKAnnotation], mapView: MKMapView) // Size the area for display and reset the view
{
var maxLat = -90.0
var minLat = 90.0
var maxLon = -180.0
var minLon = 180.0
if locations.count >= 1 {
for waypoint in locations {
maxLat = max(maxLat, waypoint.coordinate.latitude)
minLat = min(minLat, waypoint.coordinate.latitude)
maxLon = max(maxLon, waypoint.coordinate.longitude)
minLon = min(minLon, waypoint.coordinate.longitude)
}
let loc = CLLocationCoordinate2DMake((maxLat-fabs(maxLat - minLat)/2), (maxLon-fabs(maxLon - minLon)/2))
let span = MKCoordinateSpanMake(0.001 + (1.0 + Setting.shared.regionPaddingFactor) * fabs(maxLat - minLat), 0.001 + (1.0 + Setting.shared.regionPaddingFactor) * fabs(maxLon-minLon))
// The 0.001 values above ensure that you do not get a 0.0 valued span if all of the points have the same latitude, longitude, or both, or if there is only one point
// The regionPaddingFactor is a constant to allow some space around the points passed in
let reg = MKCoordinateRegionMake(loc, span)
mapView.setRegion(reg, animated: true)
mapView.animatedZoom(zoomRegion: reg, duration: 0.8)
}
}
In the calling code, I provide for 3 settings that rotate as the user presses the button:
Show a tight view (just pass current location in the call)
Show the whole route (pass all points in the template)
Change to manual zooming / positioning
The last option is needed since I call the function whenever a new current position is received to reposition the view based on current location, which repeatedly refocuses the view if the user is trying to reposition the map.
If you don't want the flexibility of sending different position arrays, you can do the positioning here using mapView.annotations or just the current location as the array.