swift - 将 NSTimer 应用于 UILabel (Swift)

Question

我对使用 swift 还很陌生，目前正在开发一个小型学校项目。然而，我似乎无法解决的一个功能是如何让 NSTimer 在一定时间后更改 UILabel 中的文本。我想将此函数应用于空白的 UILabel(无法购买)，并且刚刚更改为显示消息的文本(“您没有足够的积分”)，并且我希望删除此消息并将 UILabel 设为空白大约一秒钟后再次。谁能帮我？谢谢。

class Upgrades: UIViewController{
    @IBOutlet weak var shprogresslabel: UILabel!
    @IBOutlet weak var fsprogresslabel: UILabel!
    @IBOutlet weak var shprogress: UIProgressView!
    @IBOutlet weak var fsprogress: UIProgressView!
    @IBOutlet weak var shbutton: UIButton!
    @IBOutlet weak var fsbutton: UIButton!
    @IBOutlet weak var storepoints: UILabel!
    @IBOutlet weak var cannotbuy: UILabel!
    @IBOutlet weak var label2: UILabel!
    @IBOutlet weak var label1: UILabel!
    var fsprice = Int()
    var shprice = Int()
    let defaults = NSUserDefaults.standardUserDefaults()

    func updateProgress1(){
        fsprogress.progress += 0.1
        let fsprogressvalue = self.fsprogress.progress
        fsprogresslabel.text = "\(fsprogressvalue * 100)%"
    }
    func updateProgress2(){
        shprogress.progress += 0.2
        let shprogressvalue = self.shprogress.progress
        shprogresslabel.text = "\(shprogressvalue * 100)%"
    }


    @IBAction func button2(sender: AnyObject) {
        if shprice <= 90{

            if SharingManager.sharedInstance.totalscore >= shprice{
                SharingManager.sharedInstance.shiphealth = SharingManager.sharedInstance.shiphealth + 1
                SharingManager.sharedInstance.totalscore = SharingManager.sharedInstance.totalscore - fsprice
                storepoints.text = String(SharingManager.sharedInstance.totalscore)
                shprice = shprice + 20
                print(shprice)
                label2.text = ("\(shprice)")
                defaults.setInteger(SharingManager.sharedInstance.shiphealth, forKey: "SharingManager.sharedInstance.shiphealth")
                updateProgress2()

            }else{
                cannotbuy.text = "You dont have enough points"
            }
        }else{
            cannotbuy.text = "You have purchased all the available upgrades for this"
        }
    }
    @IBAction func button1(sender: AnyObject) {
        if fsprice <= 100{


            if SharingManager.sharedInstance.totalscore >= fsprice{

                    SharingManager.sharedInstance.bulletspeed = SharingManager.sharedInstance.bulletspeed - 0.15
                    SharingManager.sharedInstance.totalscore = SharingManager.sharedInstance.totalscore - fsprice
                    storepoints.text = String(SharingManager.sharedInstance.totalscore)
                    fsprice = fsprice + 10
                    print(fsprice)
                    label1.text = ("\(fsprice)")
                    defaults.setDouble(SharingManager.sharedInstance.bulletspeed, forKey: "SharingManager.sharedInstance.bulletspeed")
                    updateProgress1()

            }else{
                cannotbuy.text = "You dont have enough points"
        }
        }else{
            cannotbuy.text = "You have purchased all the available upgrades for this"
        }
    }

    override func viewDidLoad() {

        if fsprice == 0{
            fsprice = 10
        }
        if shprice == 0{
            shprice = 10
        }
        if fsprice == 180{
            fsbutton.enabled = false
        }
        if shprice == 100{
            shbutton.enabled = false
        }
        storepoints.text = String(SharingManager.sharedInstance.totalscore)
        label1.text = ("\(fsprice)")
        label2.text = ("\(shprice)")


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

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

Answer 1

有两种方法可以实现此目的:

使用NSTimer:

@IBAction func button2(sender: AnyObject) {
    ...
    cannotbuy.text = "You don't have enough points"
    NSTimer.scheduledTimerWithTimeInterval(5, target: self, selector: #selector(ViewController.resetCannotBuy), userInfo: nil, repeats: false)
}

func resetCannotBuy() {
    cannotbuy.text = ""
}

使用dispatch_after:

@IBAction func button2(sender: AnyObject) {
    ...
    cannotbuy.text = "You don't have enough points"

    let fiveSecondLater = dispatch_time(DISPATCH_TIME_NOW, 5 * Int64(NSEC_PER_SEC))
    dispatch_after(fiveSecondLater, dispatch_get_main_queue()) {
        self.cannotbuy.text = ""
    }
}

NSEC_PER_SEC 是每秒纳秒的常数，等于 10 亿。