Trouble with MKMapView zoom to annotation on load

Question

I'm having trouble zooming in on an annotation/pin when the MapView is loaded.

When loading the MapView, I want it to start zoomed out, and then zoom in toward the annotation/pin. The "animated" is set to "true". I'm not sure what it going wrong here.

When the map gets loaded, it briefly displays a gray screen with the pin and then the satellite map around it loads.

Thanks!

Using Swift 3

Map code:

   @IBOutlet weak var mapView: MKMapView!

   }



   override func viewDidLoad() {
       super.viewDidLoad()


       let distanceSpan:CLLocationDegrees = 300
       let redRocks:CLLocationCoordinate2D = CLLocationCoordinate2DMake(39.665496, -105.205438)
       let redRocksPin = RedRocksPin(title: "Jerry Garcia 1/2/72", subtitle: "Red Rocks Amphitheatre", coordinate: redRocks)
       mapView.addAnnotation(redRocksPin)

       mapView.setRegion(MKCoordinateRegionMakeWithDistance(redRocks, distanceSpan, distanceSpan), animated: true)

Pin Class:

import MapKit

class RedRocksPin: NSObject, MKAnnotation {
var title: String?
var subtitle: String?
var coordinate: CLLocationCoordinate2D

init(title:String, subtitle:String, coordinate: CLLocationCoordinate2D) {
    self.title = title
    self.subtitle = subtitle
    self.coordinate = coordinate
}

Answer 1

In your class declaration make these your class variables:

    let distanceSpan:CLLocationDegrees = 300
    let redRocks:CLLocationCoordinate2D = CLLocationCoordinate2DMake(39.665496, -105.205438)

In ViewWillAppear, do this:

    override func viewWillAppear(_ animated: Bool) {
       super.viewWillAppear(animted)
       view.layoutIfNeeded()

       let redRocksPin = RedRocksPin(title: "Jerry Garcia 1/2/72", subtitle: "Red Rocks Amphitheatre", coordinate: redRocks)
       mapView.addAnnotation(redRocksPin)
    }

And then this:

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        mapView.setRegion(MKCoordinateRegionMakeWithDistance(redRocks, distanceSpan, distanceSpan), animated: true)
    }

So what this does is in your viewwillAppear, it will draw the mapView, so you are able to add the annotation without causing a crash, then in the viewdidappear, it will just zoom in on the annotation you added.

Not sure if this is the best way, but something to try.