# Custom Annotation View

Add a custom annotation view

This examples shows how you can implement and use a custom ``MLNAnnotationView``.

You need to implement ``MLNMapViewDelegate/mapView:viewForAnnotation:`` of ``MLNMapViewDelegate`` which will be called when you add an ``MLNAnnotation`` to the example. In this case, three ``MLNPointAnnotation``s are added to the map. When one is selected selected ``MLNAnnotationView/setSelected:animated:`` will be called.

<!-- include-example(AnnotationViewExample) -->

```swift
class AnnotationViewExample: UIViewController, MLNMapViewDelegate {
    override func viewDidLoad() {
        super.viewDidLoad()

        let mapView = MLNMapView(frame: view.bounds)
        mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        mapView.attributionButton.isHidden = true
        mapView.tintColor = .lightGray
        mapView.centerCoordinate = CLLocationCoordinate2D(latitude: 0, longitude: 66)
        mapView.zoomLevel = 2
        mapView.delegate = self
        view.addSubview(mapView)

        // Specify coordinates for our annotations.
        let coordinates = [
            CLLocationCoordinate2D(latitude: 0, longitude: 33),
            CLLocationCoordinate2D(latitude: 0, longitude: 66),
            CLLocationCoordinate2D(latitude: 0, longitude: 99),
        ]

        // Fill an array with point annotations and add it to the map.
        var pointAnnotations = [MLNPointAnnotation]()
        for coordinate in coordinates {
            let point = MLNPointAnnotation()
            point.coordinate = coordinate
            point.title = "\(coordinate.latitude), \(coordinate.longitude)"
            pointAnnotations.append(point)
        }

        mapView.addAnnotations(pointAnnotations)
    }

    // MARK: - MLNMapViewDelegate methods

    // This delegate method is where you tell the map to load a view for a specific annotation. To load a static MLNAnnotationImage, you would use `-mapView:imageForAnnotation:`.
    func mapView(_ mapView: MLNMapView, viewFor annotation: MLNAnnotation) -> MLNAnnotationView? {
        // This example is only concerned with point annotations.
        guard annotation is MLNPointAnnotation else {
            return nil
        }

        // Use the point annotation’s longitude value (as a string) as the reuse identifier for its view.
        let reuseIdentifier = "\(annotation.coordinate.longitude)"

        // For better performance, always try to reuse existing annotations.
        var annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: reuseIdentifier)

        // If there’s no reusable annotation view available, initialize a new one.
        if annotationView == nil {
            annotationView = CustomAnnotationView(reuseIdentifier: reuseIdentifier)
            annotationView!.bounds = CGRect(x: 0, y: 0, width: 40, height: 40)

            // Set the annotation view’s background color to a value determined by its longitude.
            let hue = CGFloat(annotation.coordinate.longitude) / 100
            annotationView!.backgroundColor = UIColor(hue: hue, saturation: 0.5, brightness: 1, alpha: 1)
        }

        return annotationView
    }

    func mapView(_: MLNMapView, annotationCanShowCallout _: MLNAnnotation) -> Bool {
        true
    }
}

//
// MLNAnnotationView subclass
class CustomAnnotationView: MLNAnnotationView {
    override func layoutSubviews() {
        super.layoutSubviews()

        // Use CALayer’s corner radius to turn this view into a circle.
        layer.cornerRadius = bounds.width / 2
        layer.borderWidth = 2
        layer.borderColor = UIColor.white.cgColor
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Animate the border width in/out, creating an iris effect.
        let animation = CABasicAnimation(keyPath: "borderWidth")
        animation.duration = 0.1
        layer.borderWidth = selected ? bounds.width / 4 : 2
        layer.add(animation, forKey: "borderWidth")
    }
}
```

![](AnnotationViewExample.png)