ios - Segue 加载下一个屏幕两次

Question

我四处搜索，似乎找不到为什么我的 segue 加载下一个 View Controller 两次的答案。由于某种原因，这种情况只是偶尔发生，我想说大约是 getMyLocation 按钮被按下的 1/5 次。我希望发生的是用户按下 getMylocation 并从那里获取用户的坐标，存储数据，并使用存储的数据呈现下一个 View 。因此，我在 didUpdatedLocations 中有 performSegue ，以便我可以在调用 segue 之前存储数据。我应该注意到，segue 是通过按住 Ctrl 键单击并将主视图拖动到下一个 View 在 Storyboard中创建的，而不是通过拖动按钮来创建。

我的代码首先是第一个 View :

// Declare all IB Outlets
@IBOutlet weak var cityLabel: SpringTextField!

@IBOutlet weak var stateLabel: SpringTextField!

@IBOutlet weak var searchButton: SpringButton!

@IBOutlet weak var getLocationButton: SpringButton!

@IBOutlet weak var locationButton: UIButton!

@IBOutlet weak var citySearchButton: UIButton!

// Declare all variables

var latAndLong = ""
var city = ""
var state = ""
let locationManager = CLLocationManager()
let limitLength = 2

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {

    guard let locValue: CLLocationCoordinate2D = manager.location?.coordinate else { return }
    let lat = locValue.latitude
    let long = locValue.longitude
    latAndLong = "\(lat),\(long)"
    locationManager.stopUpdatingLocation()
    self.performSegue(withIdentifier: "goToSecond", sender: self)

}


override func viewDidLoad() {
    super.viewDidLoad()


}
override func viewDidAppear(_ animated: Bool) {


    // Declare text label delegates to allow control
    cityLabel.delegate = self as UITextFieldDelegate
    stateLabel.delegate = self as UITextFieldDelegate

    // Define what tap to look for
    let tap : UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(UIViewController.dismissKeyboard))
    tap.cancelsTouchesInView = false
    view.addGestureRecognizer(tap)

    // Delgate Location Manager
    locationManager.delegate = self
    locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters


}

// Allow keyboard to switch text fields from city to state by pressing return
internal func textFieldShouldReturn(_ textField : UITextField) -> Bool {
    if textField == cityLabel {
        city = cityLabel.text!
        textField.resignFirstResponder()
        stateLabel.becomeFirstResponder()
    }
    if textField == stateLabel {
        state = stateLabel.text!
        performSegue(withIdentifier: "goToSecond", sender: self)
    }
    return true
}
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        var newLength = 0
        if textField == stateLabel {
            guard let text = textField.text else { return true }
            newLength = text.count + string.count - range.length
            return newLength <= 2
        }
        else if textField == cityLabel {
            guard let text = textField.text else { return true }
            newLength = text.count + string.count - range.length
            return newLength <= 40
        }
       return true
    }

// Location manager required function + store location variables + perform transition to next view


// Defines what happens when either "Get My Location" or "Search by city is pressed"

@IBAction func getMyLocationPressed(_ sender: Any) {
    city = ""
    state = ""
    let status = CLLocationManager.authorizationStatus()
    if status == .authorizedWhenInUse {
        locationManager.startUpdatingLocation()
    }
        else if status == .notDetermined {
            locationManager.requestWhenInUseAuthorization()
            locationManager.startUpdatingLocation()
           return
            }
            else if status == .denied || status == .restricted {
                let alert = UIAlertController(title : "Location Services Disabled", message: "Please enable location, or search by City and State", preferredStyle: .alert)
                let okAction = UIAlertAction(title: "OK",style: .default, handler: nil)
                alert.addAction(okAction)
                present(alert, animated: true, completion: nil)
                return

    }


}
func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
    print("didnt work")
}



@IBAction func getLocationPressed(_ sender: SpringButton) {
    let status = CLLocationManager.authorizationStatus()
    if status == .notDetermined {
        locationManager.requestWhenInUseAuthorization()

        return
    }
    else if status == .denied || status == .restricted {
        let alert = UIAlertController(title : "Location Services Disabled", message: "Please enable location, or search by City and State", preferredStyle: .alert)
        let okAction = UIAlertAction(title: "OK",style: .default, handler: nil)
        alert.addAction(okAction)
        present(alert, animated: true, completion: nil)
        return
    }
    locationManager.startUpdatingLocation()

}



    // Defines what happens during transition to next screen including what variables to send ober
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "goToSecond" {
        let nextVC = segue.destination as! SecondViewController
        nextVC.cityAndState = (city) + "," + (state)
        nextVC.latAndLong = latAndLong

    }
}

}

我的第二个 View 的代码:

var latAndLong = ""
var cityAndState = ""

@IBOutlet weak var tableView: UITableView!
var selectedRow = ""
var namesOfPictures = ["Activities-1", "Food", "Drinks", "Random"]

let display = ["Activities", "Food", "Drink", "Random"]
let cellColors = ["#4D606E","#3FBAC2","#D3D4D8","#F5F5F5"]

override func viewDidLoad() {
    super.viewDidLoad()

    configureTableView()
    tableView.separatorStyle = .singleLine

    tableView.register(UINib(nibName: "TableViewCell", bundle: nil), forCellReuseIdentifier: "realCell")

    tableView.delegate = self
    tableView.dataSource = self

    // Do any additional setup after loading the view.
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "realCell", for: indexPath) as! TableViewCell
    cell.backgroundView = UIImageView(image: UIImage(named: namesOfPictures[indexPath.row]))
    cell.label.text = display[indexPath.row]
    return cell
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return display.count
}

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    print(latAndLong)
    selectedRow = display[indexPath.row]
    print(selectedRow)
    tableView.deselectRow(at: indexPath, animated: true)
    performSegue(withIdentifier: "goToActivities", sender: self)


}



func configureTableView() {
    tableView.rowHeight = 152.0

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "goToActivities" {
        let nextVC = segue.destination as! ActivitiesViewController
        nextVC.selectedItem = selectedRow
        nextVC.cityAndState = cityAndState
        nextVC.latAndLong = latAndLong
    }
}

Answer 1

CLLoction 管理器委托(delegate) - “didUpdateLocations:”即使在停止位置更新后也会多次触发

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation])

获取有效的用户位置后，您必须将 delegate 设置为 nil

 func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    //After validating user location
    locationManager.delegate = nil