ios - Swift:CALayer 边界包含 NaN:[nan nan;南南]？

Question

尽管看到了类似的答案，但我不知道这里发生了什么。我制作了一个自定义的 UIImageview，它应该在创建后立即开始动画:

class HeaderAnimator: UIImageView {

    var travelUp = Bool(false)

    var img = UIImage()

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func layoutSubviews() {
        //init

        //ALWAYS SAME COLOR - black with less opacity, just change shapes randomly via parent
        self.image = img

        UIView.animate(withDuration: 1,
                       delay: 0.2,
                       options: UIViewAnimationOptions.curveEaseIn,
                       animations: { () -> Void in
                        //animate
                        if(self.travelUp)
                        {
                             self.center.y += screenSize.height * (50/screenSize.height)
                        }
                        else {
                            self.center.y -= screenSize.height * (50/screenSize.height)
                        }

        }, completion: { (finished) -> Void in
            // ....
            print("done")
            self.removeFromSuperview()
        })

然后我尝试在另一个 View 中的计时器上生成这些 View :

let rand = Double(arc4random_uniform(4))
       var bgTimer = Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(self.animateInBg), userInfo: nil, repeats: true)

func animateInBg()
    {
        var randPos = CGPoint()
        var upOrDown = Int(arc4random_uniform(UInt32(2)))
        //print(upOrDown)

        let h = HeaderAnimator(frame: CGRect(x: 0, y: 0, width: self.bounds.width * (40/self.bounds.width), height: self.bounds.width * (40/self.bounds.width)))
        h.img = UIImage(named: "rocket")!

        switch upOrDown {
        case 0: //down
            randPos = CGPoint(x: CGFloat(arc4random()).truncatingRemainder(dividingBy: ( self.bounds.width)), y: self.bounds.height * 0.9)
            h.travelUp = false
            //h.transform = CGAffineTransform(scaleX: 1, y: -1)

        case 1: //up
            randPos = CGPoint(x: CGFloat(arc4random()).truncatingRemainder(dividingBy: ( self.bounds.width)), y: self.bounds.height * 0)
            h.travelUp = true
        default:
            randPos = CGPoint(x: CGFloat(arc4random()).truncatingRemainder(dividingBy: ( self.bounds.width)), y: self.bounds.height * 0)
            h.travelUp = true
        }

        h.center = CGPoint(x: self.bounds.width * 0.5, y: 0)
        self.addSubview(h)
    }

这些 View 应该显示出来，然后向上或向下移出 View ，然后删除。然而，在一个生成后不久，我得到错误:CALayerInvalidGeometry CALayer bounds contains NaN: [nan nan;南南]

这是什么意思？创建这些 View 我做错了什么？

Answer 1

Per Apple ，你不应该子类化 UIImageView。相反，他们建议您将 UIView 子类化并在那里进行绘图。

Do not use image views for custom drawing. TheUIImageView class does not draw its content using the draw(_:) method. Use image views only to present images. To do custom drawing involving images, subclass UIView directly and draw your image there.