check if MKMarkerAnnotationView is cluttered or decluttered in MKMapView

Question

I have done Clustering for Points by referencing the below example provided by apple. https://developer.apple.com/documentation/mapkit/mkannotationview/decluttering_a_map_with_mapkit_annotation_clustering

I wanted to know wether there is any method which gets called when the annotations are cluttered & decluttered.

Or

How I can come to know that particular annotation is cluttered and decluttered as I need to run some code block for that.

Answer 1

How I can come to know that particular annotation is cluttered and decluttered.

Check within MKClusterAnnotation.memberAnnotations if a MKAnnotation is present, like so:

func isCluttered(annotation: MKAnnotation) -> Bool {
    let clusters = mapView.annotations.filter({ $0 is MKClusterAnnotation }) as! [MKClusterAnnotation]
    for cluster in clusters {
        if cluster.memberAnnotations.first(where: { $0 === annotation }) != nil {
            return true
        }
    }
    return false
}

Usage: picks a random annotation from mapView

let annotations = mapView.annotations.filter { $0 is Cycle }
let randomIndex = Int(arc4random_uniform(UInt32(annotations.count)))
if (isCluttered(annotation: annotations[randomIndex])) {
    print("Cluttered")
} else {
    print("Not cluttered")
    mapView.selectAnnotation(annotations[randomIndex], animated: true)
}

check if MKMarkerAnnotationView is cluttered or decluttered in MKMapView

MKMarkerAnnotationView is a subclass of MKAnnotationView, and you can override setSelected(_:animated:), for an example open ClusterAnnotationView.swift from your linked sample code and paste this:

override func setSelected(_ selected: Bool, animated: Bool) {
    let cluster = annotation as? MKClusterAnnotation
    print("\(selected ? "Selecting" : "Deselected") Clustered Annotation \(cluster?.memberAnnotations.count ?? -1)")
}

Similarly you can override the setSelected(_:animated:) method in each MKMarkerAnnotationView in CycleAnnotationView.swift, paste in all 3 classes:

override func setSelected(_ selected: Bool, animated: Bool) {
    print("\(selected ? "Selecting" : "Deselected") unclustered annotation with type: \(clusteringIdentifier!)")
}

Now run and tap annotations on map and check Debug area for print messages.