用户使用swift单击表格视图中的单元格之一后，如何运行计时器？

Question

I have two view controllers in my UI and what I am aiming to do is as soon as the user clicks on one of the cells in the table view, a pop up will appear (the other view controller) with a timer

However, when I build the app and click on one of the cells the label still says label and does not count down

I am also getting an error saying Unicode curly quote found replace with "" and expected digit after integer literal prefix in the same line (I indicated which line it is below)

this class is for the view controller with the table view

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


    public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
    {

//bringing down the array to print

        let cell = UITableViewCell(style: UITableViewCellStyle.default, reuseIdentifier: "cell")
        cell.textLabel?.text = redeem[indexPath.row]

        return(cell)
    }


    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath)
    {


        let popOverVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "sbPopUpID") as! PopUpViewController

        self.addChildViewController(popOverVC)
        popOverVC.view.frame = self.view.frame
        self.view.addSubview(popOverVC.view)
        popOverVC.didMove(toParentViewController: self)


    }   

This class is for the PopUpViewController

import UIKit

class PopUpViewController: UIViewController
{

    @IBOutlet weak var timerLabel: UILabel!

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

     var seconds = 60
     var timer = Timer()
     var isTimeRunning = false

     override func viewDidLoad()
     {
         super.viewDidLoad()


         self.view.backgroundColor = UIColor.black.withAlphaComponent(0.8)


     }

     func runTimer()
     {
         timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: (#selector(PopUpViewController.updateTimer)), userInfo: nil, repeats: true)
     }

     func timeString(time:TimeInterval) -> String
     {
         let hours = Int(time) / 3600
         let minutes = Int(time) / 60 % 60
         let seconds = Int(time) % 60
//getting the error message for the line below
         return String(format:”%02i:%02i:%02i”, hours, minutes, seconds)
     }

     func updateTimer()
     {
         if seconds < 1
         {
             self.view.removeFromSuperview()
         }
         else
         {
             seconds -= 1
//getting an error message here saying EXC_BAD_INSTRUCTION (unexpectedly found nil while unwrapping an Optional value)
             timerLabel.text = timeString(time: TimeInterval(seconds))
         }

     }

Answer 1

1. I don't see any call to runTimer . So the timer never starts. I suggest using viewWillAppear or viewDidAppear . Add this to PopupViewController:

    override func viewWillAppear(_ animated: Bool) { super.viewWillAppear(animated) runTimer() } 

2. You just call self.view.removeFromSuperview() to close the popup, which removes the view from view hierarchy but the viewController is still registered as child viewController. I suggest presenting the popup with presentViewController and removing it with dismissViewControllerAnimated .

Present the view controller:

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath)
    {
        let popOverVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "sbPopUpID") as! PopUpViewController

        self.present(popOverVC, animated: true, completion: nil)
    }

Dismiss it with:

    @IBAction func closePopUp(_ sender: Any)
    {
        self.dismiss(animated: true, completion: nil)
    }

3. You have used the wrong quotes (” instead of "), hence the error.

Answer 2

Basic code needed. Remember, you need to make sure whenever you make a new timer to make sure to have invalidate() called on the existing one or you will spawn multiple timers where you probably don't want to.

class myClass: UIViewController {
    //...
    var timer:Timer!
    //...
    func createTimer(interval: TimeInterval, selector: Selector) {
        if timer == nil {
            timer = Timer.scheduledTimer(timeInterval: interval, target: self, selector: selector , userInfo: nil, repeats: true)
        }
    }
    //...
    func cancelTimer() {
        timer.invalidate()
        timer = nil
    }
    //...
    override func viewWillDisappear(_ animated: Bool) {
        cancelTimer()
    }
}