ios - 如何将 selectedSegmentIndex 的值传递给另一个 viewController？

Question

我有一个 PopUpViewController，当在主 ViewController 中按下按钮时，它会弹出。我在三个不同的 ViewController 上有一个 speedDisplay (UILabel)，我希望能够在 MPH 和 KMH 之间切换输出，但我不知道该怎么做。我在 PopUpViewController 中有一个 segmentControl，我正在尝试实现它以实现这一点。有人可以帮我从这里出去吗？

import UIKit

public enum Speed {
case KMH
case MPH
}
protocol PopUpViewControllerDelegate: class {

func selectedSpeedType(_ type: Speed)
}

class PopUpViewController: UIViewController, UIGestureRecognizerDelegate {

weak var delegate: PopUpViewControllerDelegate?


@IBOutlet weak var altitudeSegment: UISegmentedControl!
@IBOutlet weak var tempSegment: UISegmentedControl!
@IBOutlet weak var speedSC: UISegmentedControl!

@IBOutlet weak var doneButton: UIButton!
@IBOutlet weak var settingsView: UIView!



override func viewDidLoad() {
    super.viewDidLoad()
    self.view.backgroundColor = UIColor.black.withAlphaComponent(0.8)

    settingsView.layer.masksToBounds = true
    settingsView.layer.cornerRadius = 8

    doneButton.layer.masksToBounds = true
    doneButton.layer.cornerRadius = 8

    let items = ["MPH", "KMH"]
    let segmentedControl = UISegmentedControl.init(items: items)
    segmentedControl.selectedSegmentIndex = 0        
    segmentedControl.addTarget(self, action: #selector(speedChoice(_sender:)), for: UIControl.Event.valueChanged)
    self.view.addSubview(segmentedControl)

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

@IBAction func speedChoice(_ sender: UISegmentedControl) {

    let index = sender.selectedSegmentIndex

    switch index {
    case 0:
        // Needs to euqal MPH to use on speedDisplay in another viewController
    case 1:
        // Needs to euqal KMH to use on speedDisplay in another viewController
    default:
        break
    }
}

这是我在 ViewController 上的速度函数:

override func viewDidLoad() {
    super.viewDidLoad()
    getCurrentDateTime()
    self.locationManager.requestWhenInUseAuthorization()

    if CLLocationManager.locationServicesEnabled() {
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.startUpdatingLocation()
        locationManager.startUpdatingHeading()
        locationManager.headingFilter = 5
    }
     func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    map.mapType = MKMapType.standard
    let location = locations[0]
    let myLocation: CLLocationCoordinate2D = CLLocationCoordinate2DMake(location.coordinate.latitude, location.coordinate.longitude)
    let span = MKCoordinateSpan(latitudeDelta: 0.02, longitudeDelta: 0.02)
    let region = MKCoordinateRegion(center: myLocation, span: span)
    map.setRegion(region, animated: true)
    self.map.showsUserLocation = true

    let speed = location.speed
    if speed < 2 {
        self.speedDisplay.text = "0.0"
    }
    else {
        if speedType == .MPH {
            self.speedDisplay.text = String(format: "%.1f", speed * 2.236936284, "MPH")
            speedTypeLabel.text = "MPH"
        }
        else {
            self.speedDisplay.text = String(format: "%.1f", speed * 3.6, "KMH")
            speedTypeLabel.text = "KMH"
        }
    }
extension ViewController: PopUpViewControllerDelegate {
    func selectedSpeedType(_ type: Speed) {
        speedType = type
    }
}

以及弹出窗口的代码:

@IBAction func showPopup(_ sender: Any) {

    let popOverVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "sbPopUpID") as! PopUpViewController
    self.addChild(popOverVC)
    popOverVC.view.frame = self.view.frame
    self.view.addSubview(popOverVC.view)
    popOverVC.didMove(toParent: self)

    }

}

我有以下用于保存 segmentedController 的内容:我相信我遗漏了一些东西，因为每次我选择一个段时它都会返回到段 0。它打印出来就像它正在工作但它没有保存选择。有什么想法吗？

@IBAction func closePopUp(_ sender: UIButton) {
    self.view.removeFromSuperview()
    }

Answer 1

使用 delegate 机制将数据从一个 ViewController 发送回另一个。

在 PopUpViewController 内部

import UIKit

public enum Speed {
    case KMPH
    case MPH
}
protocol PopUpViewControllerDelegate: class {

    func selectedSpeedType(_ type: Speed)
}

class PopUpViewController: UIViewController, UIGestureRecognizerDelegate {

    weak var delegate: PopUpViewControllerDelegate?

    //This is global variable (internal protection level) and can be get/set from outside of the class.
    var speedType = Speed.KMPH //New line

    @IBOutlet weak var altitudeSegment: UISegmentedControl!

    ......
    ......

    override func viewDidLoad() {
        super.viewDidLoad()

        .......

        //We can select the segment control with corresponding value even popover is removed from the ViewController.
        altitudeSegment.selectedSegmentIndex = speedType.hashValue //New line
    }

    @IBAction func speedChoice(_ sender: Any) {

        let segmentControl = sender as! UISegmentedControl
        if segmentControl.selectedSegmentIndex == 0 {
            delegate?.selectedSpeedType(.KMPH)
        } else {
            delegate?.selectedSpeedType(.MPH)
        }
    }
}

在 YourViewController 中:

class ViewController: UIViewController {

    var speedType: Speed! = .KMPH
    var popOverVC: PopUpViewController!

    override func viewDidLoad() {
        super.viewDidLoad()

        popVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "sbPopUpID") as! PopUpViewController
        popVC.delegate = self
    }

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

        .....

        self.speedDisplay.text = "\(String(format: "%.1f", speed * 2.236936284)) \((speedType == .KMPH) ? "KMPH" : "MPH")"
    }

    @IBAction func showPopup(_ sender: Any) {

        self.addChild(popOverVC)
        popOverVC.view.frame = self.view.frame
        //Assign the speedType to selected value back in PopOverViewController, and update the segmentControl to new value.
        popOverVC.speedType = speedType //New line
        self.view.addSubview(popOverVC.view)
        popOverVC.didMove(toParent: self)
    }
}

extension ViewController: PopUpViewControllerDelegate {

    func selectedSpeedType(_ type: Speed) {

        speedType = type
    }
}