ios - 快速改变图层颜色

Question

目前在我的应用程序中，当用户点击屏幕时，用户触摸的任何地方都会出现一个红点，如果用户多次点击屏幕，则会出现多个点。我想添加一个功能来允许用户更改颜色。

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first as UITouch?{
        let location = (touch as! UITouch).location(in: self.imageView)
        let layer = CAShapeLayer()

        layer.path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath
        layer.fillColor = UIColor.red.cgColor

        imageView.layer.addSublayer(layer)
    }
}

当我尝试以下方法时，我可以更改颜色，但由于某种原因，无论我在屏幕上点击多少次，都只会有一个点。我的猜测是，每次我点击屏幕时都会创建一个新图层并替换旧图层。无论如何，我可以允许用户更改图层的颜色，同时保留图层上已有的所有点吗？

class ViewController: UIViewController,UIScrollViewDelegate      {
    let layer = CAShapeLayer()
    override func viewDidLoad() {
        super.viewDidLoad()
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let touch = touches.first as UITouch?{
            let location = (touch as! UITouch).location(in: self.imageView)


            layer.path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath
            layer.fillColor = UIColor.red.cgColor

            imageView.layer.addSublayer(layer)
        }
    }
    @IBAction func changecolorBtn(_ sender: Any) {
        layer.fillColor = UIColor.green.cgColor
    }
}

Answer 1

因为你只用了一层

let layer = CAShapeLayer()

无论何时设置

layer.path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath

它将删除旧路径，并且您的新路径只有​​一个点。

这就是为什么

When I tried the following method I am able to change the colour but for some reason no matter how many times I've tap on the screen there will only be one dot.

您可以通过组合所有点路径来简单地解决您的问题。像这样

// add the combine path as your global variable
let layer = CAShapeLayer()
let combinePath = CGMutablePath()

并更改您的添加路径代码

layer.path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath

添加组合路径

let path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath
combinePath.addPath(path)
layer.path = combinePath