Question

美好的一天

我似乎有一个简单的问题，但是我无法解决这个问题。

我在视图控制器内部有一个容器视图。在那个容器里，我几乎没有标签。容器具有自己的视图控制器。在容器的视图控制器中，我正在运行一个计时器，并且我希望该标签显示该计时器。但是每次我使用该标签时，应用都会崩溃 “线程1：致命错误：在展开可选值时意外发现nil”

如果我注释带有此标签的行，则一切运行正常。

    @IBOutlet weak var timeLabel: UILabel!

var counter = 0.0
var timer = Timer()
var isRunning = false


func startStopTimer () {
    if isRunning {
        timer.invalidate()
        isRunning = false
    }else {
        timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(updateTimer), userInfo: nil, repeats: true)
        isRunning = true
    }
}

@objc func updateTimer() {
    counter = counter + 0.1

    timeLabel.text = String(counter) 
}

这是我第一次在主故事板中使用容器视图。

知道我做错了什么或有建议的人可以尝试改变的人吗？

谢谢乔纳斯（Jonas）

完整代码

    class MainViewController: UIViewController {
@IBOutlet weak var topContainer: UIView!
@IBOutlet weak var informationContainer: UIView!

@IBOutlet weak var startStopButtonOutlet: UIButton!

let informationContainerVC = InformationContainerViewController()

override func viewDidLoad() {
    super.viewDidLoad()

    setupView()
}

func setupView() {
    topContainer.layer.cornerRadius = 5
    topContainer.layer.masksToBounds = true

    informationContainer.layer.cornerRadius = 5
    informationContainer.layer.masksToBounds = true

    startStopButtonOutlet.layer.cornerRadius = 5
    startStopButtonOutlet.layer.masksToBounds = true
}

@IBAction func startStopButton_TouchUpInside(_ sender: UIButton) {
    informationContainerVC.startStopTimer()

    UIButton.animate(withDuration: 0.1, delay: 0.0, options: [.allowUserInteraction, .curveEaseOut], animations: {
        sender.transform = CGAffineTransform.identity

    }, completion: nil)

    if informationContainerVC.isRunning {
        startStopButtonOutlet.setTitle("Push to Pause", for: .normal)
    }else {
        startStopButtonOutlet.setTitle("Push to Start", for: .normal)
    }
}

@IBAction func startStopButton_TouchDown(_ sender: UIButton) {
    UIButton.animate(withDuration: 0.1, delay: 0.0, options: [.allowUserInteraction, .curveEaseIn], animations: {
        sender.transform = CGAffineTransform(scaleX: 0.9, y: 0.9)

        if self.informationContainerVC.isRunning {

            sender.backgroundColor = UIColor.white.withAlphaComponent(0.5)
        }else {
            sender.backgroundColor = UIColor.green.withAlphaComponent(0.8)
        }



    }, completion: nil)
}

@IBAction func startStopButton_TouchUpOutside(_ sender: UIButton) {
    UIButton.animate(withDuration: 0.1, delay: 0.0, options: [.allowUserInteraction, .curveEaseOut], animations: {
        sender.transform = CGAffineTransform.identity

    }, completion: nil)
}
}

这是容器视图控制器的代码

class InformationContainerViewController: UIViewController {

@IBOutlet weak var timeLabel: UILabel!

var counter = 0.0
var timer = Timer()
var isRunning = false


func startStopTimer () {
    if isRunning {
        timer.invalidate()
        isRunning = false
    }else {
        timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(updateTimer), userInfo: nil, repeats: true)
        isRunning = true
    }
}

@objc func updateTimer() {
    counter = counter + 0.1

    timeLabel.text = String(counter)

}
}

Answer 1

说let informationContainerVC = InformationContainerViewController()时，您正在创建一个InformationContainerViewController的新实例，该实例未链接到情节提要，因此未设置任何出口。

您需要获得对容器视图中实际存在的视图控制器实例的引用。您可以在prepare(for segue:)中进行；如果查看情节提要，您会发现有一个嵌入的segue将您的包含视图控制器链接到包含的视图控制器。

在您的MainViewController中：

var informationContainerVC: InformationContainerViewController?

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    if let destVC = segue.destination as? InformationContainerViewController {
        self.informationContainerVC = destVC
    }
}

@IBAction func startStopButton_TouchUpInside(_ sender: UIButton) {
    informationContainerVC?.startStopTimer()

    UIButton.animate(withDuration: 0.1, delay: 0.0, options: [.allowUserInteraction, .curveEaseOut], animations: {
        sender.transform = CGAffineTransform.identity

    }, completion: nil)

    if informationContainerVC?.isRunning {
        startStopButtonOutlet.setTitle("Push to Pause", for: .normal)
    } else {
        startStopButtonOutlet.setTitle("Push to Start", for: .normal)
    }
}

现在您将引用正确的视图控制器实例

（UILabel）无，无法在标签中插入文本

1 个答案: