Question

我的代码是在达到2秒时尝试停止计时器。那就是我现在所拥有的不起作用，我也不知道还能做些什么。我认为viewdidappear会起作用。我认为反制是我应该做的if声明。

import UIKit
class ViewController: UIViewController {
@IBOutlet var playbutton: UIButton!
@IBOutlet var titlelabel: UILabel!

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


override func viewDidLoad() {
    super.viewDidLoad()
    titlelabel.text = "\(counter)"
    playbutton.isEnabled = true

}
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        if counter == 1.9 {
            timer.invalidate()
        }
    }

@IBAction func btnreset(_ sender: UIButton) {
    timer.invalidate()
    titlelabel.text = "\(counter)"
    counter = 0
    playbutton.isEnabled = true

    isRunning = false
}
@IBAction func btnplay(_ sender: UIButton) {
    if !isRunning{
        timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(UpdateTime), userInfo: nil, repeats: true)
        playbutton.isEnabled = false
    isRunning = true
    }

}
@objc func UpdateTime(){
    counter += 0.1
    titlelabel.text = String(format: "%.1f", counter)

}}

Answer 1

有一些问题。

将计时器声明为可选，然后您可以删除isRunning变量，如果计时器不在nil

，则计时器正在运行

var timer : Timer?

...

@IBAction func btnplay(_ sender: UIButton) {
    if timer == nil {
        timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(updateTime), userInfo: nil, repeats: true)
        playbutton.isEnabled = false
    }
}

必须在updateTime功能中检查计时器是否超过2秒，因为它经常被调用。 viewDidAppear只被调用一次。

检查== 1.9无法可靠地运行，因为浮点值不完全是1.9。
检查是否等于或大于

@objc func updateTime()
{
    counter += 0.1
    titlelabel.text = String(format: "%.1f", counter)
    if counter >= 1.9 {
        timer?.invalidate()
        timer = nil
    }
}

在btnreset中检查计时器是否正在运行并将其重置为nil

@IBAction func btnreset(_ sender: UIButton) {
    if timer != nil {
        timer!.invalidate()
        timer = nil
        titlelabel.text = "\(counter)"
        counter = 0
        playbutton.isEnabled = true
    }
}

if语句取决于计时器

1 个答案: