Google 从 firebase 检索到的地图标记

Question

创建标记后，它们会立即显示在地图和数据库中。但是当我删除它时，它会保留在地图中，直到我更新视图。我想立即将其从地图中删除，但不知道如何操作。有什么建议吗？

这就是我从 firebase 检索数据并在 for cicle

中显示标记的方式

let ref = FIRDatabase.database().reference().child("userdata")
ref.observe(.childAdded, with: { (snapshot) in
    ref.observe(FIRDataEventType.value, with: { (snapshot) in
        if (snapshot.value as? [String:Any]) != nil {
            for rest in snapshot.children.allObjects as! [FIRDataSnapshot] {
                guard let Dict = rest.value as? [String: AnyObject] else {
                    continue
                }
                let latitude = Dict["latitude"]
                let longitude = Dict["longitude"]
                let username = Dict["username"]
                let model = Dict["firstname"]
                let marker = GMSMarker()
                marker.position = CLLocationCoordinate2D(latitude: latitude as! CLLocationDegrees, longitude: longitude as! CLLocationDegrees)
                marker.title = username as? String
                marker.snippet = model as? String
                mapView.selectedMarker = marker
                marker.map = mapView
            }
        }
    })
})

我还把我用来创建标记的函数也放在了

func mapView(_ mapView: GMSMapView, didLongPressAt coordinate: CLLocationCoordinate2D) {
        print("You tapped at \(coordinate.latitude), \(coordinate.longitude)")
        let alertController = UIAlertController(title: "Crea Marker", message: "...", preferredStyle: UIAlertControllerStyle.alert) //Replace UIAlertControllerStyle.Alert by UIAlertControllerStyle.alert
        let DestructiveAction = UIAlertAction(title: "Annulla", style: UIAlertActionStyle.cancel) {
            (result : UIAlertAction) -> Void in
            print("Annulla")
        }

        // Replace UIAlertActionStyle.Default by UIAlertActionStyle.default
        let okAction = UIAlertAction(title: "Crea", style: UIAlertActionStyle.default) {
            (result : UIAlertAction) -> Void in
            let ref = FIRDatabase.database().reference().child("userdata")
            let currentUser = FIRAuth.auth()?.currentUser
            let displayName = currentUser?.displayName
            let post = ["username": displayName,"uid": currentUser?.uid as Any,"latitude": coordinate.latitude,"longitude": coordinate.longitude, "firstname":"test"]
            ref.childByAutoId().setValue(post)

            print("Entra")
        }

        alertController.addAction(DestructiveAction)
        alertController.addAction(okAction)
        self.present(alertController, animated: true, completion: nil)
    }

N.B。我从 Firebase

手动删除数据

编辑： This is a gif for a better explain

Answer 1

根据我的经验，您正在再次调用 firebase 数据或再次刷新它

如果是，则必须使用以下方法清除地图

let ref = FIRDatabase.database().reference().child("userdata")
ref.observe(.childAdded, with: { (snapshot) in
    ref.observe(FIRDataEventType.value, with: { (snapshot) in
        if (snapshot.value as? [String:Any]) != nil {

           //Here Before adding any other marker You have to clear your MAP 
           mapView.clear()

            for rest in snapshot.children.allObjects as! [FIRDataSnapshot] {
                guard let Dict = rest.value as? [String: AnyObject] else {
                    continue
                }
                let latitude = Dict["latitude"]
                let longitude = Dict["longitude"]
                let username = Dict["username"]
                let model = Dict["firstname"]
                let marker = GMSMarker()
                marker.position = CLLocationCoordinate2D(latitude: latitude as! CLLocationDegrees, longitude: longitude as! CLLocationDegrees)
                marker.title = username as? String
                marker.snippet = model as? String
                mapView.selectedMarker = marker
                marker.map = mapView
            }
        }
    })
})

它将解决您在 MAP 上使用旧标记的问题

但是，如果您不刷新数据，请在要刷新此数据或删除标记的地方使用此 mapView.clear() 方法。

查看下方 link 参考：

https://developers.google.com/maps/documentation/ios-sdk/marker

Google 从 firebase 检索到的地图标记

Google Map markers retrieved from firebase

google-maps

google-maps-markers

ios

swift