Question

我在代码中添加了MapView，MKUserTrackingButton按钮，localManager，DispatchGroup：

let mapView: MKMapView = {
    let mapView = MKMapView()
    mapView.translatesAutoresizingMaskIntoConstraints = false
    return mapView
}()

private var userTrackingButton: MKUserTrackingButton!
private let locationManager = CLLocationManager()
let myGroup = DispatchGroup()
var array = [Car]()

在ViewDidLoad中，我设置了：

myGroup.enter()

从Firebase获取数据：

observeCars()

等待，直到我从Firebase中获取所有数据：

    myGroup.notify(queue: DispatchQueue.main) {
        self.view.addSubview(self.mapView)

        //Here code to set the mapView in the view

        self.setupUserTrackingButton()
        self.locationManager.delegate = self
        self.locationManager.requestWhenInUseAuthorization()
        self.locationManager.startUpdatingLocation()
    }

在这里，我在视图中设置按钮：

private func setupUserTrackingButton() {
    mapView.showsUserLocation = true
    userTrackingButton = MKUserTrackingButton(mapView: mapView)
    userTrackingButton.layer.backgroundColor = UIColor(white: 0.5, alpha: 1).cgColor
    userTrackingButton.layer.borderColor = UIColor.white.cgColor
    userTrackingButton.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(userTrackingButton)
    ///Code to set in the view the button
}

我设置与Firebase的连接以获取数据的类：

class APIService: NSObject {
    class func observeCars(completion: ((_ car: Car) -> Void)?) {
    let ref = Database.database().reference()
       ref.child("Cars").observe(.childAdded, with: { (snapshot) in
            if let dictionary = snapshot.value as? [String: Any] {
                let car = Car(dictionary: dictionary)
                completion?(car)
            }
        }, withCancel: nil)
    }

}

这是函数（用MainViewController编写），我从Firebase中获取数据并将其添加到数组中：

internal func observeCars() { 
    /////I think this is the part that makes It doesn't appear because 
    if I delete this part, it works like I aspect
    APIService.observeCars {
        (car) in
        self.array.append(car)
        print(self.array.count)
        if self.array.count == totalCars {
            self.myGroup.leave()
        }
    }
     //////////
    }

有任何提示吗？谢谢

Answer 1

我在mapView中添加了MKUserTrackingButton：

mapView.addSubview(userLocationButton)

对我有用。

MKUserTrackingButton不会因为Firebase出现？

1 个答案: