Question

在我的iOS测验应用中，您可以在15秒内回答问题。如果回答正确，则出现第二个视图控制器，而不是从第二个视图控制器上的按钮单击中解除，并且第一个视图控制器重新出现，并显示要回答的新问题。但是，倒计时器会在您单击问题的答案后立即启动，而不是在您单击第二个视图控制器上的按钮以关闭第二个视图控制器时。我希望倒数计时器能够在第二个视图控制器上的按钮被解除后立即重置，并向原始视图控制器显示一个新问题。实现这一目标的最佳方法是什么？

这是我的代码（第一个视图控制器）：

import UIKit

extension ViewController: QuizCompletedDelegate {
    func continueQuiz() {
        questionTimer.text = String(counter)
    }
}

class ViewController: UIViewController {

    //random image func
    func randomImage() {
        index = Int(arc4random_uniform(UInt32(questionImages.count)))
        questionImage.image = questionImages[index]
    }

    var questionList = [String]()

    func updateCounter() {
        counter -= 1
        questionTimer.text = String(counter)

        if counter == 0 {            
            timer.invalidate()
            wrongSeg()
        }
    }

    func randomQuestion() {        
        //random question
        if questionList.isEmpty {
            questionList = Array(QADictionary.keys)
            continueQuiz()            
        }

        let rand = Int(arc4random_uniform(UInt32(questionList.count)))
        questionLabel.text = questionList[rand]

        //matching answer values to go with question keys
        var choices = QADictionary[questionList[rand]]!

        questionList.remove(at: rand)

        //create button
        var button:UIButton = UIButton()

        //variables
        var x = 1
        rightAnswerBox = arc4random_uniform(4)+1

        for index in 1...4
        {
            button = view.viewWithTag(index) as! UIButton

            if (index == Int(rightAnswerBox))
            {
                button.setTitle(choices[0], for: .normal)
            }
            else {
                button.setTitle(choices[x], for: .normal)
                x += 1    
            }   
            randomImage()
            continueQuiz()
        }
    }

    let QADictionary = ["Who is Thor's brother?" : ["Atum", "Loki", "Red Norvell", "Kevin Masterson"], "What is the name of Thor's hammer?" : ["Mjolinr", "Uru", "Stormbreaker", "Thundara"], "Who is the father of Thor?" : ["Odin", "Sif", "Heimdall", "Balder"]]

    //wrong view segue
    func wrongSeg() {        
        performSegue(withIdentifier: "incorrectSeg", sender: self)        
    }

    //proceed screen
    func rightSeg() {    
        performSegue(withIdentifier: "correctSeg", sender: self)
    }

    //variables
    var rightAnswerBox:UInt32 = 0
    var index = 0

    //Question Label
    @IBOutlet weak var questionLabel: UILabel!

    //Answer Button
    @IBAction func buttonAction(_ sender: AnyObject) {
        if (sender.tag == Int(rightAnswerBox))
        {
            rightSeg()
            print ("Correct!")
        }

        if counter != 0 {

        }
        else if (sender.tag != Int(rightAnswerBox)) {
            wrongSeg()
            print ("Wrong!")
            timer.invalidate()
            questionList = []
        }
    }

    override func viewDidAppear(_ animated: Bool)
    {
        randomQuestion()
    }

    //variables
    var counter = 15

    var timer = Timer()

    @IBOutlet weak var questionTimer: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        timer = Timer.scheduledTimer(timeInterval: 1, target:self, selector: #selector(ViewController.updateCounter), userInfo: nil, repeats: true)        
    }

代码到第二个视图控制器：

import UIKit

protocol QuizCompletedDelegate {
    func continueQuiz()
}

class ContinueScreen: UIViewController {

    var delegate: QuizCompletedDelegate?

    //correct answer label
    @IBOutlet weak var correctLbl: UILabel!

    //background photo
    @IBOutlet weak var backgroundImage: UIImageView!

    func backToQuiz() {
        if let nav = self.navigationController {
            nav.popViewController(animated: true)    
        }
        else {
            self.dismiss(animated: true, completion: nil)
        }
    }

    @IBAction func `continue`(_ sender: Any) {
        backToQuiz()
        delegate?.continueQuiz()
    }

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

Answer 1

您可以在第一个视图控制器上实现viewDidAppear（）函数，当您的第二个视图控制器被解除时，将自动调用此函数，因此会再次看到第一个。

因此，在第一个视图控制器中创建此功能：

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    // HERE PUT YOUR TIMER RESET
    // ...
}

Answer 2

您的代码存在问题buttonAction。如果选择了错误的答案，则invalidate计时器。但是，如果你的答案是正确的，你不会对计时器做任何事情，并允许它继续。

要暂停计时器，您需要使其无效，然后重新创建它。那么，你能做的就是：

//Answer Button
@IBAction func buttonAction(_ sender: AnyObject) {
    if (sender.tag == Int(rightAnswerBox))
    {
        timer.invalidate() // Pause the current timer
        rightSeg()
        print ("Correct!")
    }

    if counter != 0 {

    }
    else if (sender.tag != Int(rightAnswerBox)) {
        wrongSeg()
        print ("Wrong!")
        timer.invalidate()
        questionList = []
    }
}

要再次创建计时器，您需要添加：

timer = Timer.scheduledTimer(timeInterval: 1, target:self, selector: #selector(ViewController.updateCounter), userInfo: nil, repeats: true)

当视图出现时，您将添加此计时器：

override func viewDidAppear(_ animated: Bool)
    {
        timer = Timer.scheduledTimer(timeInterval: 1, target:self, selector: #selector(ViewController.updateCounter), userInfo: nil, repeats: true)

    }

请注意，如果您在viewDidAppear中添加计时器，则应删除viewDidLoad中的计时器，否则您将在应用程序加载时创建两个计时器。

从viewDidLoad中删除计时器后，该函数现在应如下所示：

override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

 }

总之，这里的想法是：当你得到正确的答案时，你想暂停计时器（使用timer.invalidate），然后当视图出现时，你会创建一个新的计时器。

如何让我的倒数计时器重置到每次视图加载？

2 个答案: