Swift:延迟增加标签 [英] Swift: Incrementing label with delay

问题描述

当我的应用程序到达这部分代码时，它会冻结.我试图以半秒的延迟增加一个数字，然后将其打印到屏幕上.所以标签文本会变成 1，然后是 2，然后是 3，等等.我把这段代码扔到了操场上，DispatchQueue 似乎无限上升.谢谢.

My app freezes when it reaches this part of the code. I am attempting to increment a number with a half of a second delay, then printing that to the screen. So the label text would turn into a 1, then a 2, then a 3, etc. I threw this code into playground and the DispatchQueue seems to infinitely go up. Thanks.

var percentage = 0

func incrementLabel (amount: Int){
    var count = 0
    while count <= amount{
        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5, execute: {
            percentage += 1
            count += 1
        })
    }
}

incrementLabel(amount: 10)
print(percentage)

推荐答案

这里有一个替代解决方案，您可以使用它来代替 DispatchQueue:

Here is an alternative solution that you could use instead of DispatchQueue:

var percentage = 0
var counter = 0
var timer: Timer?

func incrementLabel(amount: Int) {
    counter = amount
    timer = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(self.updateDelay), userInfo: nil, repeats: true)
}

@objc func updateDelay() {
    if (counter > 0) {
        counter -= 1

        percentage += 1
    } else {
        timer.invalidate()
        timer = nil
    }
}

incrementLabel(amount: 10)
print(percentage)

这在 Swift 中使用了 Timer.

This uses Timer in Swift.

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