按下主页按钮时如何使ios应用程序停止[重复]

Question

我的应用上有一个页面，当按下按钮时会运行一个计数器。当我转到另一个页面或通过双击主页完全终止应用程序并将其滑开时，它会停止运行。这对我来说很好，正是我想要它做的。即使应用程序仍在运行，我也希望当我按下主页按钮时计数器停止，我希望计数器停止。我会在下面贴出我的计数器。

class Miner: UIViewController {

//Start
@IBOutlet weak var startMining: UIButton!

//Coin Label
@IBOutlet weak var coinLabel: UILabel!

//Counter
var count:Int {
    get {
        return UserDefaults.standard.integer(forKey: "count")
    }
    set {
        UserDefaults.standard.set(newValue, forKey: "count")
        coinLabel.text = "Coins: 0. \(newValue)"

    }
}
var counting:Bool = false
var timer:Timer = Timer()




override func viewDidLoad() {


    super.viewDidLoad()


}

@objc func counter() -> Void {

    count += 1
    coinLabel.text = "Coins: 0." + String(count)
    walletLabel.text = "Wallet: 0." + String(count)

}

@IBAction func startMining(_ sender: Any) {
    if counting {
        // Stop Counting
        startMining.setTitle("Start", for: .normal)

        timer.invalidate()

        counting = false


    } else if !counting {
        // Start Counting
        startMining.setTitle("Stop", for: .normal)
        // Start timer
        timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector (counter), userInfo: nil, repeats: true)
        counting = true
    }



}

}

Answer 1

override func viewDidLoad() {
    super.viewDidLoad()

    NotificationCenter.default.addObserver(self, selector: #selector(appDidEnterBackground), name: .UIApplicationDidEnterBackground, object: nil)
}

func appDidEnterBackground() {
    // stop counter
}