当我将 nil 传递给 view 参数时，convert(_ rect: CGRect, to view: UIView?) 什么都不做

Question

我正在尝试在超级视图的本地坐标中获取视图的坐标。因此，根据文档，如果 view 为 nil，则此方法将改为转换为窗口基坐标。所以就我而言，它什么也没做，但如果我将视图传递给它，它就可以工作。

let zoomImageView = UIImageView()
let xoomImageView2 = UIImageView()
let xoomImageView3 = UIImageView()
let stratingFrame2 = CGRect(x: 20, y: 10, width: 150, height: 130)
let startingFrame1 = CGRect(x: 40, y: 20, width: 200, height: 160)
let startingFrame = CGRect(x: 0, y: 200, width:375, height: 200)

override func viewDidLoad() {
    super.viewDidLoad()
    xoomImageView3.frame = stratingFrame2
    xoomImageView3.backgroundColor = UIColor.purple
    xoomImageView2.frame = startingFrame1
    xoomImageView2.backgroundColor = UIColor.black
    zoomImageView.frame = startingFrame
    zoomImageView.backgroundColor = UIColor.red
    zoomImageView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(animate)))
    zoomImageView.isUserInteractionEnabled = true
 //   zoomImageView.image = UIImage(named: "zuckdog")
    zoomImageView.contentMode = .scaleAspectFill
    zoomImageView.clipsToBounds = true
    view.addSubview(zoomImageView)
    zoomImageView.addSubview(xoomImageView2)
    xoomImageView2.addSubview(xoomImageView3)
    print(zoomImageView.frame)
    print(xoomImageView2.frame)
    print(xoomImageView3.frame)

    let newFrame = zoomImageView.convert(xoomImageView3.frame, to:  nil)
    print(newFrame)

也许有人能说出发生了什么？

Answer 1

如果你想在坐标中转换一个主要规则是

视图必须是子视图到用户坐标的转换方法

现在看看你的代码

let newFrame = zoomImageView.convert(xoomImageView3.frame, to:  nil)
print(newFrame)

zoomImageView 在您的代码中从来不是子视图 xoomImageView3，还有一件事 xoomImageView3 与 zoomImageView 对象没有直接关系

你需要做的是

首先将xoomImageView3 帧转换为zoomImageView

 let xoomImageView3FrameAccordingTo_zoomImageView  = xoomImageView2.convert(xoomImageView3.frame, to:  zoomImageView)

现在

let newFrame = zoomImageView.convert(xoomImageView3FrameAccordingTo_zoomImageView, to:  self.view)