swift - 使用计时器从 uitextfield 中放置的内容开始倒计时

Question

下面的快速代码应该采用文本字段中放置的任何数字，然后按一秒倒计时。我不知道如何获取文本字段中的内容并对其进行倒数。不必担心确保用户在文本字段中放置的是数字而不是字符串。

    import UIKit

class ViewController: UIViewController {

var enterTime = UITextField()
var lblTime = UILabel()
var startBTN = UIButton()
var timer = Timer()
var counter = 33

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.

    [enterTime,lblTime,startBTN].forEach{
        $0.backgroundColor = .systemRed
        view.addSubview($0)
        $0.translatesAutoresizingMaskIntoConstraints = false
    }

     enterTime.frame = CGRect(x: view.center.x-115, y: view.center.y-200, width: 60, height: 50)
     lblTime.frame = CGRect(x: view.center.x-115, y: view.center.y, width: 60, height: 50)
     startBTN.frame = CGRect(x: view.center.x-115, y: view.center.y+200, width: 60, height: 50)

    startBTN.addTarget(self, action: #selector(startHit), for: .touchDown)


}
@objc func startHit() {

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



}

    @objc func timerAction() {



        //This is where the user would take the time from uitextfield and causes it to count down
        enterTime.text = counter

        lblTime.text = "\(counter)"
    }
}

Answer 1

1 ) 使计时器无效并使用 EnterTime 文本字段中的值启动计数器，并在 startHit 函数中启动计时器。

2 ) 在timerAction函数中，将计数器值减1并设置到lblTime中。

您可能需要如下修改 startHit 和 timerAction 函数。

@objc func startHit() {
   timer.invalidate()
   if let counterText = enterTime.text, let counterValue = Int(counterText) {
      counter = counterValue
      lblTime.text = String(counter)
      timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
   }      
}

@objc func timerAction() {
   counter -= 1
   lblTime.text = String(counter)
   if ( counter == 0 ) {
      timer.invalidate()
   }
}