导航栏未悬停在mapview swift上4

Question

我正在尝试构建一个应用程序，用户可以在其中单击地图视图顶部的导航栏中的按钮按钮项。但是，导航栏固定在页面顶部，我希望它位于中间，以便将鼠标悬停在mapview上。有什么办法做到这一点，我在stackoverflow页面上找不到答案。谢谢

我已经尝试将其添加为子视图，并且尝试更改mapview和导航栏的约束

IBOutlet weak var navBar: UINavigationItem!
    @IBOutlet weak var textField: UITextField!
    @IBOutlet weak var map: MKMapView!
    let manager = CLLocationManager()
    var latitude: Double = 0.0
    var longitude: Double = 0.0
    var overlays = [MKOverlay]()
    var locations = [Message]()
    override func viewDidLoad() {
        super.viewDidLoad()
        ref =  Database.database().reference()
        manager.delegate = self
        manager.desiredAccuracy = kCLLocationAccuracyBest
        manager.requestAlwaysAuthorization()
        manager.requestLocation()
        manager.startUpdatingLocation()

        textField.backgroundColor = UIColor.white
        textField.layer.masksToBounds = false
        textField.layer.shadowColor = UIColor(displayP3Red: 0, green: 0, blue: 0, alpha: 0.9).cgColor
        textField.layer.shadowOffset = CGSize(width: 0, height: 2)
        textField.layer.shadowOpacity = 0.6
        textField.backgroundColor = .white
        // Do any additional setup after loading the view, typically from a nib.

        map.addSubview(navBar as! UIView)
    }

地图视图不会停留在页面中间。