Ios Swift Timer.scheduledTimer（）不'；行不通_Ios_Swift_Timer

Ios Swift Timer.scheduledTimer（）不'；行不通

ios swift timer

Ios Swift Timer.scheduledTimer（）不'；行不通,ios,swift,timer,Ios,Swift,Timer,我的swift应用程序中有两个视图。我正在表演一段，如下所示 ViewController.swift----------------->GameViewController.swift func signIn(difficultyLvl:String){ let username = usernameTxt.text let password = passwordTxt.text let url = URL(string: "http://192.168.1.106/

我的swift应用程序中有两个视图。我正在表演一段，如下所示

ViewController.swift----------------->GameViewController.swift

func signIn(difficultyLvl:String){
    let username = usernameTxt.text
    let password = passwordTxt.text

    let url = URL(string: "http://192.168.1.106/speed/scoreBoardController.php?username="+username!+"&password="+password!+"&action=SIGNIN")

    let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
        let isPassed = String(data: data!, encoding:.utf8)?.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)

        var gameViewControllerParams = [Int: [String: String]]()
        gameViewControllerParams[0] = ["userId" : isPassed!]
        gameViewControllerParams[1] = ["difficultyLvl" : difficultyLvl]

        if(isPassed != "null"){
            self.performSegue(withIdentifier: "gotoGame", sender: gameViewControllerParams)
        }
    }

    task.resume()
}

class GameViewController: UIViewController {

    var gameViewControllerParams = [Int: [String: String]]()

    override func viewDidLoad() {
        super.viewDidLoad()

        let _ = Timer.scheduledTimer(timeInterval: 1.0, target:self, selector: #selector(self.setCalculationLs), userInfo:nil,repeats: true)
    }

    func setCalculationLs(){
        print("Timing")
    }

}

加载GameViewController时，值数组也从ViewController.swift传递到GameViewController.swift

func signIn(difficultyLvl:String){
    let username = usernameTxt.text
    let password = passwordTxt.text

    let url = URL(string: "http://192.168.1.106/speed/scoreBoardController.php?username="+username!+"&password="+password!+"&action=SIGNIN")

    let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
        let isPassed = String(data: data!, encoding:.utf8)?.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)

        var gameViewControllerParams = [Int: [String: String]]()
        gameViewControllerParams[0] = ["userId" : isPassed!]
        gameViewControllerParams[1] = ["difficultyLvl" : difficultyLvl]

        if(isPassed != "null"){
            self.performSegue(withIdentifier: "gotoGame", sender: gameViewControllerParams)
        }
    }

    task.resume()
}

class GameViewController: UIViewController {

    var gameViewControllerParams = [Int: [String: String]]()

    override func viewDidLoad() {
        super.viewDidLoad()

        let _ = Timer.scheduledTimer(timeInterval: 1.0, target:self, selector: #selector(self.setCalculationLs), userInfo:nil,repeats: true)
    }

    func setCalculationLs(){
        print("Timing")
    }

}

应在GameViewController.swift中初始化计时器

func signIn(difficultyLvl:String){
    let username = usernameTxt.text
    let password = passwordTxt.text

    let url = URL(string: "http://192.168.1.106/speed/scoreBoardController.php?username="+username!+"&password="+password!+"&action=SIGNIN")

    let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
        let isPassed = String(data: data!, encoding:.utf8)?.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)

        var gameViewControllerParams = [Int: [String: String]]()
        gameViewControllerParams[0] = ["userId" : isPassed!]
        gameViewControllerParams[1] = ["difficultyLvl" : difficultyLvl]

        if(isPassed != "null"){
            self.performSegue(withIdentifier: "gotoGame", sender: gameViewControllerParams)
        }
    }

    task.resume()
}

class GameViewController: UIViewController {

    var gameViewControllerParams = [Int: [String: String]]()

    override func viewDidLoad() {
        super.viewDidLoad()

        let _ = Timer.scheduledTimer(timeInterval: 1.0, target:self, selector: #selector(self.setCalculationLs), userInfo:nil,repeats: true)
    }

    func setCalculationLs(){
        print("Timing")
    }

}

我试图初始化一个计时器并通过它调用一个方法，但它不起作用

以下是我的代码片段

ViewController.swift

func signIn(difficultyLvl:String){
    let username = usernameTxt.text
    let password = passwordTxt.text

    let url = URL(string: "http://192.168.1.106/speed/scoreBoardController.php?username="+username!+"&password="+password!+"&action=SIGNIN")

    let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
        let isPassed = String(data: data!, encoding:.utf8)?.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)

        var gameViewControllerParams = [Int: [String: String]]()
        gameViewControllerParams[0] = ["userId" : isPassed!]
        gameViewControllerParams[1] = ["difficultyLvl" : difficultyLvl]

        if(isPassed != "null"){
            self.performSegue(withIdentifier: "gotoGame", sender: gameViewControllerParams)
        }
    }

    task.resume()
}

class GameViewController: UIViewController {

    var gameViewControllerParams = [Int: [String: String]]()

    override func viewDidLoad() {
        super.viewDidLoad()

        let _ = Timer.scheduledTimer(timeInterval: 1.0, target:self, selector: #selector(self.setCalculationLs), userInfo:nil,repeats: true)
    }

    func setCalculationLs(){
        print("Timing")
    }

}

GameViewController.swift

func signIn(difficultyLvl:String){
    let username = usernameTxt.text
    let password = passwordTxt.text

    let url = URL(string: "http://192.168.1.106/speed/scoreBoardController.php?username="+username!+"&password="+password!+"&action=SIGNIN")

    let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
        let isPassed = String(data: data!, encoding:.utf8)?.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)

        var gameViewControllerParams = [Int: [String: String]]()
        gameViewControllerParams[0] = ["userId" : isPassed!]
        gameViewControllerParams[1] = ["difficultyLvl" : difficultyLvl]

        if(isPassed != "null"){
            self.performSegue(withIdentifier: "gotoGame", sender: gameViewControllerParams)
        }
    }

    task.resume()
}

class GameViewController: UIViewController {

    var gameViewControllerParams = [Int: [String: String]]()

    override func viewDidLoad() {
        super.viewDidLoad()

        let _ = Timer.scheduledTimer(timeInterval: 1.0, target:self, selector: #selector(self.setCalculationLs), userInfo:nil,repeats: true)
    }

    func setCalculationLs(){
        print("Timing")
    }

}

计时器不能在后台队列上工作（没有一些技巧，包括创建运行循环或在现有运行循环上手动调度）。但无论如何，您不应该从主队列以外的任何地方启动任何UI更新

因此，由于您是从

URLSession

完成闭包（在后台队列上运行）调用

performsgue

，因此它实际上也是从后台队列运行

viewdiload

。因此，计划计时器的尝试失败。要解决此问题，您必须手动将

performsgue

代码分派到主队列：

let task = URLSession.shared.dataTask(with: url!) { data, response, error in
    ...

    if isPassed != "null" {
        DispatchQueue.main.async {
            self.performSegue(withIdentifier: "gotoGame", sender: ...)
        }
    }
}

如果您不确定某些代码是否正在主队列上运行，请参阅。或者，您可以使用分派前提条件：

dispatchPrecondition(condition: .onQueue(.main))

这样，如果您意外地从后台队列调用了代码，它将（在调试版本中）停止应用程序

与您当前的问题无关，但另一方面，为了避免计时器和视图控制器之间的强引用循环，您通常希望保留对计时器的引用，以便在视图消失时使其失效（例如，在

视图显示中创建计时器，并在视图显示中删除计时器）. 否则，您可能会在退出后保留GameViewController
，例如：
class GameViewController: UIViewController {

    weak var timer: Timer?

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

        timer = Timer.scheduledTimer(timeInterval: 1.0, target:self, selector: #selector(setCalculationLs(_:)), userInfo: nil, repeats: true)
    }

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

        timer?.invalidate()
    }

    @objc func setCalculationLs(_ timer: Timer) {
        print("Tick")
    }
}

或者，在iOS 10或更高版本中，您可以使用基于块的变量，并在deinit
中引用self
，和invalidate
：
class GameViewController: UIViewController {

    weak var timer: Timer?

    override func viewDidLoad() {
        super.viewDidLoad()

        timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] timer in
            self?.setCalculationLs()
        }
    }

    deinit {
        timer?.invalidate()
    }

    func setCalculationLs() {
        print("Tick")
    }

}

我觉得在定时器中设置目标对象有问题。任何建议。感谢您没有将数组发送到GameViewController
，请在prepare（for:sender:）
中执行此操作。sender
参数应该是self
到底是什么问题？GameViewController是否已加载？是否调用viewDidLoad（）？阵列传递与计时器问题有何关系通常，计时器代码应该可以工作。此外，请确保从主队列调用performsgue
。触发UI更改的东西总是必须从主线程发生。而且，巧合的是，如果您尝试在后台线程上创建计时器，它将不起作用（除非您创建运行循环，这在这里您肯定不想做）。@paper1111实际上准备（for:sender:）在我的代码中。我没能把我的问题包括进去。你能再检查一下吗？噢！成功了。非常感谢您的支持。这将对像我这样的新手非常有帮助。而且，我将尝试更改我的应用程序逻辑，不从主队列以外的任何地方启动UI更新。再次感谢您，您更喜欢[弱自我]方法还是viewDidLoad/ViewDidEvale方法？谢谢。我更喜欢[weak self]
模式，但有时您必须使用旧的API，因为您支持旧的iOS版本。如果从技术上讲，您仍然使用旧的API，而我的示例是viewDidLoad
/viewdiddemouse
，那么我可能会建议viewdide出现
和viewdidemouse
（因为这些将始终保持平衡，而viewDidLoad
可能不会与viewdiddemove
调用保持平衡，特别是当您以模式显示另一个视图控制器时）.我只使用了上面的viewDidLoad
，因为这就是OP在原始问题中创建计时器的地方。我喜欢苹果在文档中提到计时器不适用于后台队列…等等，他们不适用。“计时器不适用于后台队列”我终于找到你了！谢谢）