scrollView contentOffset y 更改时如何动态更改字体大小? [英] How change font size dynamically when scrollView contentOffset y changed?

问题描述

我有 UIScrollView 和 UILabel.当用户向上/向下滚动我的 UIScrollView.

I have UIScrollView and UILabel. I want to change UILabel size dynamically from 33.0 to 0.0 , 0.0 to 33 when user scroll up / down my UIScrollView.

我该怎么做?

@IBOutlet weak var myLabel : UILabel!

override func viewDidLoad() {
    super.viewDidLoad()

    scrollView.delegate = self
}

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let offset = scrollView.contentOffset.y
    let fontpointmath = (myLabel.font.pointSize / (offset / 100) - 15)

    if offset > 0 {
        if fontpointmath < 0 {
            myLabel.font =  UIFont(name: "Arial", size: 0.0)
        }else if fontpointmath > 33 {
            myLabel.font =  UIFont(name: "Arial", size: 33.0)
        }else{
            myLabel.font =  UIFont(name: "Arial", size: CGFloat(fontpointmath))
        }
    }

我当前的代码只允许字体大小为 15 点左右，不会更改为 0.当用户再次向下滚动时，它也不会增加到 33.

My current code only allow font size to about 15 points and doesn't change to 0. It also doesn't go up to 33 when user scroll down again.

推荐答案

请尝试使用transform来代替改变字体大小

Please try to use transform instead font size changing

override func viewDidLoad() {
    super.viewDidLoad()
    scrollView.delegate = self
    myLabel.font = UIFont(name: "Arial", size: 33.0)
}

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let offset = scrollView.contentOffset.y
    let scale = min(max(1.0 - offset / 200.0, 0.0), 1.0)
    myLabel.transform = CGAffineTransform(scaleX: scale, y: scale)
}  

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