我知道这个问题已经问了很多次了，但是所有的答案似乎都与我的应用程序中发生的事情略有不同。
我的理解是，一旦mapView将其委托设置为ViewController（在其中显示它），并且当mapView滚动以使其显示在mapView区域内时，将向Map添加注解，则将调用viewForAnnotation函数。
目前，我有一个主视图控制器（mainVC），其中包含一个MKMapView（mapView）。该视图控制器控制四个不同的Map，以在mapView中显示。

func moveViews(sender:Int) {
    // This function handles which button on the Segmented Control was clicked and the loads the appropriate map into the mapView (passed as a para

    removeAnnotationsAndOverlays() // ~~~
    if sender == 0 {
        // First Map was selected
        let map1VC = map1VC()
        map1VC.loadMap1View(mapView)
        map1VC.centerMapOnLocation()
    }
    else if sender == 1 {
        // Second Map was selected
        let map2VC = map2VC()
        map2VC.loadMap2View(mapView)
    }
    else if sender == 2 {
        // Third Map was selected
        let map3VC = map3VC()
        map3VC.loadMap3View(mapView)
    }
    else if sender == 3 {
        // Fourth Map was selected
        let map4VC = map4VC()
        map4VC.loadMap4View(mapView)
    }
    else {
        // Load First Map as default
        let map1VC = map1VC()
        map1VC.loadMap1View(mapView)
        map1VC.centerMapOnLocation()
    }
}

有几个不同的类控制每个不同Map的功能：
1.Map1 -显示从plist读取的MKPolylines和自定义注解（继承自MKAnnotation）的组合-这工作得很好！
1.Map2 -显示从plist中读取的几条MKPolyline-这很好用！
1.Map3 -显示从plist读取的几条MKPolyline-这很好用！
1.标测图4 -应显示多个自定义注解-这不起作用！
以下是Map 4的情况：

• MKMapView正在正确加载

var mapView: MKMapView = MKMapView() // declared as a global variable/object inside the map4VC()

// Initial function to set up Map
//      Think of this function as the "override func viewDidLoad() {}"
func loadMap4View(mV: MKMapView) {

// This connects the parameter passed (mV) and sets it as the delegate for the mapView used throughout this file
//      In other words, it allows the mapView on the MainVC to use all of the code in this file to handle different actions
mapView = mV
mapView.delegate = self

let initialLocation = CLLocation(latitude: 50.3603125, longitude: 2.794017)

// calculates the region you'll look at on the screen 
let coordinateRegion = MKCoordinateRegionMakeWithDistance(initialLocation.coordinate, regionRadius, regionRadius)

// sets the region of the map
mapView.setRegion(coordinateRegion, animated: true)

//addPins()  // This can use a custom function to load all of the Pins
//mapView.addAnnotations(coords.allLocations!) // This line also works to add all of the individual pins

mapView.addAnnotation(coords.allLocations![2]) // This adds one single Pin

}

• 将mapView的委托设置为当前类（mapView.delegate = self）
• 它会放大适当的位置（mapView.setRegion（coordinateRegion，animated：正确））
• 该类从plist中读取，并（使用helper类）构建自定义MKAnnotations（CemAnnno）数组
• 这些位置存储在CemAnno的一个名为allLocations的数组中：

var allLocations: [CemAnno]? = [] // This is declared in the helper class along with a bunch of other stuff that grabs all of the information from a plist

 class CemAnno: NSObject, MKAnnotation {

var coordinate: CLLocationCoordinate2D
var title: String?
var casualties: String?
var visitInfo: String?
var histInfo: String?
var region: String?

init(title: String, coordinate: CLLocationCoordinate2D, region: String, casualties: String, visitInfo: String, histInfo: String) {

self.coordinate = coordinate
self.title = title
self.region = region
self.casualties = casualties
self.visitInfo = visitInfo
self.histInfo = histInfo
}

}

// This builds an object inside the the map4VC() class called coords that holds all of the information collected from the plist
var coords = BuildCoordinates(filename: "Coordinate")

• 将每个标注添加到Map（mapView.addAnnotations），并将它们显示为大头针（它们正在显示）mapView.addAnnotation（coords.allLocations！[2]）//这将添加一个大头针标注（可以工作），但不会调用viewForAnnotation函数

这是可行的，但是，我试图自定义正在显示的注解，但ViewForAnnotation函数从未被调用？？？

// This function is NEVER called
func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView?
{
    // Define a reuse identifier. This is a string that will be used to ensure we reuse annotation views as much as possible.
    let identifier = "CemAnno"

    // Check whether the annotation we're creating a view for is one of our CemAnno objects.
    if annotation.isKindOfClass(CemAnno.self) {
        print("correct class")
        //let anno = annotation as! CustomAnnotation
        // Try to dequeue an annotation view from the map view's pool of unused views.
        var annotationView = mapView.dequeueReusableAnnotationViewWithIdentifier(identifier)

        if annotationView == nil {
            print("no reusable view")
            // If it isn't able to find a reusable view, create a new one using MKPinAnnotationView and sets its canShowCallout property to be true. This triggers the popup with the name.
            annotationView = MKPinAnnotationView(annotation: annotation, reuseIdentifier: identifier)
            annotationView!.canShowCallout = true

            // Create a new UIButton using the built-in .Custom type. This is so we can add an image to the button.
            let btn = UIButton(type: .DetailDisclosure)
            //btn.setImage(anno.image, forState: .Normal)
            annotationView!.rightCalloutAccessoryView = btn
        } else {
            print("reusing a view")
            // If it can reuse a view, update that view to use a different annotation.
            annotationView!.annotation = annotation
        }

        return annotationView

    }

    // If the annotation isn't from a CustomClass, it must return nil so iOS uses a default view.
    return MKPinAnnotationView()
}

我试过在Map的当前视图区域内添加大头针的位置，但ViewForAnnotation始终没有被触发。我试过在Map的当前视图区域外添加大头针的位置，但ViewForAnnotation始终没有被触发-我想这应该是一个有效的方法，当我“滚动”Map时，它会显示在应该触发该函数的当前视图区域内。但它没有（我应该注意到大头针正在显示，并显示在Map上）。

这使得我无法自定义我想做的引脚。

我使用的技术与Map 1相同，它工作得非常好，但由于某种原因，ViewForAnnotation从未在Map 4中调用。
任何建议都将不胜感激！！