Question

当我按下按钮时，会出现带有标签的视图。然后我希望标签消失并重新出现5次（带动画），每次标签重新出现时都会显示不同的文字。我似乎无法获得任何代码来动画UILabel并更改文本。我试过这个。但是，当我按下按钮时，循环和动画会立即发生。

持续时间如下：0.3,0.6,0.9,1.2,1.5

for i in 1...5 {

            infoViewMsgLbl.text = randomReward(real: i) // This retrives a String

            UIView.animate(withDuration: ((1.5/5)*Double(i)), delay: 0.0, options: .allowAnimatedContent, animations: { 
                self.infoViewMsgLbl.alpha = 0
            }, completion: { finished in
                UIView.animate(withDuration: ((1.5/5)*Double(i)), animations: { 
                    self.infoViewMsgLbl.alpha = 1
                })
            })

            print("in the loop: ", i)
        }

Answer 1

您正在更改duration，但将delay保留为0（即立即开始）。在这些情况下，您可以反过来改变delay并保持duration不变。

但是考虑到你想要更改标签text，我可能会改用计时器：

var index = 1
Timer.scheduledTimer(withTimeInterval: 0.3, repeats: true) { [weak self] timer in
    self?.infoViewMsgLbl.alpha = 0
    self?.infoViewMsgLbl.text = self?.randomReward(real: index)
    index += 1
    if index > 5 { timer.invalidate() }
    UIView.animate(withDuration: 0.3) {
        self?.infoViewMsgLbl.alpha = 1
    }
}

Answer 2

也许是这样的：

func animate(alpha: CGFloat, start: Int, end: Int) {

    infoViewMsgLbl.text = randomReward(real: Int(start/2)) // This retrives a String

    UIView.animate(withDuration: 0.3, animations: {
        self.infoViewMsgLbl.alpha = alpha
    }, completion: { success in

        if start + 1 <= end {
            self.animate(alpha: alpha == 1.0 ? 0.0 : 1.0, start: start + 1, end: end)
        }
    })
}

用法：

animate(alpha:0.0, start: 0, end: 10)  //would flash a total of 5 times

请注意，持续时间保持为0.3，因为它不会调用下一个循环，直到每增加0.3秒为止。

如何使UILabel出现并消失5次？

2 个答案: