UIView bounds.applying 但有旋转

Question

我想在视图周围创建一个虚线边框，可以移动/旋转/缩放。

这是我的代码：

func addBorder() {        
    let f = selectedObject.bounds.applying(selectedObject.transform)
    borderView.backgroundColor = UIColor(red: 1, green: 0, blue: 0, alpha: 0.5) //just for testing
    borderView.frame = f
    borderView.center = selectedObject.center
    borderView.transform = CGAffineTransform(translationX: selectedObject.transform.tx, y: selectedObject.transform.ty)

    removeBorder() //remove old border

    let f2 = CGRect(x: 0, y: 0, width: borderView.frame.width, height: borderView.frame.height)
    let dashedBorder = CAShapeLayer()
    dashedBorder.strokeColor = UIColor.black.cgColor
    dashedBorder.lineDashPattern = [2, 2]
    dashedBorder.frame = f2
    dashedBorder.fillColor = nil
    dashedBorder.path = UIBezierPath(rect: f2).cgPath
    dashedBorder.name = "border"
    borderView.layer.addSublayer(dashedBorder)
}

它看起来像这样：

这还不错，但我希望边框也可以旋转，因为它可能会误导用户，因为触摸区域仅在图像上。

我尝试对变换应用旋转：

func addBorder() {        
    let f = selectedObject.bounds.applying(selectedObject.transform)
    borderView.backgroundColor = UIColor(red: 1, green: 0, blue: 0, alpha: 0.5) //just for testing
    borderView.frame = f
    borderView.center = selectedObject.center
    let rotation = atan2(selectedObject.transform.b, selectedObject.transform.a)

    borderView.transform = CGAffineTransform(rotationAngle: rotation).translatedBy(x: selectedObject.transform.tx, y: selectedObject.transform.ty)

    removeBorder() //remove old border

    let f2 = CGRect(x: 0, y: 0, width: borderView.frame.width, height: borderView.frame.height)
    let dashedBorder = CAShapeLayer()
    dashedBorder.strokeColor = UIColor.black.cgColor
    dashedBorder.lineDashPattern = [2, 2]
    dashedBorder.frame = f2
    dashedBorder.fillColor = nil
    dashedBorder.path = UIBezierPath(rect: f2).cgPath
    dashedBorder.name = "border"
    borderView.layer.addSublayer(dashedBorder)
}

但旋转后是这样的：

我该如何解决这个问题？

Answer 1

这是一个基于您的代码的示例：

//initial transforms
selectedObject.transform = CGAffineTransform.init(rotationAngle: .pi / 4).translatedBy(x: 150, y: 15)

func addBorder() {
    let borderView = UIView.init(frame: selectedObject.bounds)
    self.view.addSubview(borderView)
    borderView.backgroundColor = UIColor(red: 1, green: 0, blue: 0, alpha: 0.5) //just for testing
    borderView.center = selectedObject.center
    borderView.transform = selectedObject.transform

    removeBorder() //remove old border

    let dashedBorder = CAShapeLayer()
    dashedBorder.strokeColor = UIColor.black.cgColor
    dashedBorder.lineDashPattern = [2, 2]
    dashedBorder.fillColor = nil
    dashedBorder.path = UIBezierPath(rect: borderView.bounds).cgPath
    dashedBorder.name = "border"
    borderView.layer.addSublayer(dashedBorder)
}

Answer 2

这里是for问题的解决方案：

func addBorder() {

    borderView.backgroundColor = UIColor(red: 1, green: 0, blue: 0, alpha: 0.5) //just for testing
    let degrees: CGFloat = 20.0 //the value in degrees for rotation
    let radians: CGFloat = degrees * (.pi / 180)
    borderView.transform = CGAffineTransform(rotationAngle: radians)

    removeBorder()

    let dashedBorder = CAShapeLayer()
    dashedBorder.strokeColor = UIColor.black.cgColor
    dashedBorder.lineDashPattern = [2, 2]
    dashedBorder.frame = borderView.bounds
    dashedBorder.fillColor = nil
    dashedBorder.path = UIBezierPath(roundedRect: borderView.bounds, cornerRadius:0).cgPath
    dashedBorder.name = "border"
    borderView.layer.addSublayer(dashedBorder)
}

以上代码在 Xcode 10 和 Swift 4.2 中测试

Answer 3

即使我已经接受了答案，因为它帮助我理解了我发布最终答案的问题，因为它更重要。而且我认为它对其他人有帮助，因为我在 Stackoverflow 或其他地方找不到这个解决方案。

这个想法是创建一个borderView，其边界与selectedObject 相同。这是来自@Incredible_dev 的解决方案，但是有一个问题：当borderView 向任何方向缩放时，线本身会延伸。我想保持线的大小，只是想在selectedObject附近。所以，我将selectedObject 的边界与从selectedObject.transform 提取的比例相乘。然后我从selectedObject 复制平移和旋转。

这是最终代码：

var borderView: UIView!
var selectedObject: UIView?

extension CGAffineTransform { //helper extension

    func getScale() -> CGFloat {
        return (self.a * self.a + self.c * self.c).squareRoot()
    }

    func getRotation() -> CGFloat {
        return atan2(self.b, self.a)
    }

}

func removeBorder() { //remove the older border
    if borderView != nil {
        borderView.removeFromSuperview()
    }
}

func addBorder() {
    guard let selectedObject = selectedObject else { return }

    removeBorder() //remove old border

    let t = selectedObject.transform
    let s = t.getScale()
    let r = t.getRotation()

    borderView = UIView(frame: CGRect(x: 0, y: 0, width: selectedObject.bounds.width * s, height: selectedObject.bounds.height * s)) //multiply bounds with selectedObject's scale
    dividerImageView.addSubview(borderView) //add borderView to the "scene"

    borderView.transform = CGAffineTransform(translationX: t.tx, y: t.ty).rotated(by: r) //copy translation and rotation, order is important
    borderView.center = selectedObject.center

    let dashedBorder = CAShapeLayer() //create 2-point wide dashed line
    dashedBorder.lineWidth = 2
    dashedBorder.strokeColor = UIColor.black.cgColor
    dashedBorder.lineDashPattern = [2, 2]
    dashedBorder.fillColor = nil
    dashedBorder.path = UIBezierPath(rect: borderView.bounds).cgPath
    borderView.layer.addSublayer(dashedBorder)
}