Swift 3.0 Map viewForAnnotation不輸出正確標註

Question

我無法理解viewForAnnotation方法的代碼以及何時調用它。我的意圖是根據引腳顏色的顏色顯示特定的標註。在第一次加載mapView時，標註顯示正確，但是在切換視圖控制器後，根據引腳顏色不能正確顯示標註按鈕。我有一個預感，這可能與viewForAnnotation調用時有關（無論每次出現地圖時調用它）。我無法弄清楚什麼是錯誤的，因爲我不確定代碼的每個部分是幹什麼的。

func mapView(_ map: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? { 

if (annotation is MKUserLocation) { 

    return nil 
} 

let identifier = "pinAnnotation" 


// In particular I am not sure what the code below does 

if let pin = annotation as? ColorPointAnnotation { 


    if let view = map.dequeueReusableAnnotationView(withIdentifier: identifier) as? MKPinAnnotationView { 
     view.annotation = annotation 
     view.pinTintColor = pin.color ?? .purple 

     return view 

    } else { 

     let view = MKPinAnnotationView(annotation: annotation, reuseIdentifier: identifier) 
     view.isEnabled = true 

     view.canShowCallout = true 

     view.pinTintColor = pin.color ?? .purple 

     let btn = UIButton(type: .detailDisclosure) 
     view.rightCalloutAccessoryView = btn 


     if view.pinTintColor == .red || view.pinTintColor == .green { 
      let button = UIButton(frame: CGRect(x: 0, y: 0, width: 30, height: 30)) 
      button.setBackgroundImage(UIImage(named: "car"), for: .normal) 
      button.addTarget(self, action: #selector(MapVC.getDirections), for: .touchUpInside) 
      view.leftCalloutAccessoryView = button 
     } else { 
      let button = UIButton(frame: CGRect(x: 0, y: 0, width: 30, height: 30)) 
      button.setBackgroundImage(UIImage(named: "other"), for: .normal) 
      button.addTarget(self, action: #selector(MapVC.other), for: .touchUpInside) 
      view.leftCalloutAccessoryView = button 
     } 

     return view 
    } 
} 

if let annotationView = map.dequeueReusableAnnotationView(withIdentifier: identifier) { 
    annotationView.annotation = annotation 
    return annotationView 
} else { 
    let annotationView = MKPinAnnotationView(annotation:annotation, reuseIdentifier: identifier) 
    annotationView.isEnabled = true 
    annotationView.canShowCallout = true 

    let btn = UIButton(type: .detailDisclosure) 
    annotationView.rightCalloutAccessoryView = btn 

    if annotationView.pinTintColor == .red || annotationView.pinTintColor == .green { 

     let smallSquare = CGSize(width: 120, height: 120) 
     let button = UIButton(frame: CGRect(origin: CGPoint(x: 0,y :0), size: smallSquare)) 
     button.setBackgroundImage(UIImage(named: "car"), for: .normal) 
     button.addTarget(self, action: #selector(MapVC.getDirections), for: .touchUpInside) 
     annotationView.leftCalloutAccessoryView = button 
    } else { 
     let button = UIButton(frame: CGRect(x: 0, y: 0, width: 30, height: 30)) 
     button.setBackgroundImage(UIImage(named: "other"), for: .normal) 
     button.addTarget(self, action: #selector(MapVC.other), for: .touchUpInside) 
     annotationView.leftCalloutAccessoryView = button 
    } 

    return annotationView 
} 

} 

Answer 1

方法func mapView(_ map: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView?是MapViewDelegate的委託方法，這個方法，每次執行您的MapView顯示批註在一個地區的時間，而如果實現了您可以顯示annotationView任何子類如地圖annotationView，顯示自定義標註需要實現MapViewDelegate

//example code 
func mapView(_ mapView: MKMapView, didSelect view: MKAnnotationView){ 
    let customCallout = CustomCallout(frame: CGRect(x: 0, y: 0, width: self.view.frame.size.width * 0.8, height: 50)) 
    customCallout.backgroundColor = UIColor.red //your color here 
    view.addSubView(customCallout) 
    //adjust any param you need here 
} 

希望這種方法這可以幫助你