Swift obtain visible annotations/clusters shown in map

问题

I'm currently developing an app where I load user images as an annotation onto a map. Currently, I use an API to load images in viewForAnnotation for each image annotation and if the user has more than a few thousand photos, this image loading function is called every time and degrades performance significantly.

Is there anyway I can obtain just the annotations which are shown on the map currently, i.e. only the annotations and clusters of annotations that are visible to the user? Apple's API for annotations(in:) using visibleMapRect returns basically every single annotation whereas I just want the high-level or currently displaying annotation. For example, in the image linked below, there are 2 annotations appearing but these 2 annotations are clusters of hundreds of annotations. Is there any way to just load image for these two instead of every single annotation?

回答1:

You can do you check like this:

func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
    if annotation is MKClusterAnnotation {
        // Need to load images
    }
    ...
}

来源：https://stackoverflow.com/questions/51144550/swift-obtain-visible-annotations-clusters-shown-in-map