Question

我是swift和iOS的新手，有些东西我不知道该怎么做。

我的颜色来自后端，我想将其转换为CGColor

"colors": [
        "6909A1",
        "7552D1",
        "59B0DC",
        "62E3CC"
      ],

func drawGradient(colors: [CGColor]) {
        addLayer(colors: colors)
    }

在从JSON转换后，我应该怎么做才能传递CGColor数组。我找不到如何从简单的String

获取CGColor的正确解决方案

Answer 1

UInt有一个方便的初始值设定项，可将十六进制字符串转换为十六进制值

func color(from hexString : String) -> CGColor
{
  if let rgbValue = UInt(hexString, radix: 16) {
    let red   =  CGFloat((rgbValue >> 16) & 0xff) / 255
    let green =  CGFloat((rgbValue >>  8) & 0xff) / 255
    let blue  =  CGFloat((rgbValue      ) & 0xff) / 255
    return UIColor(red: red, green: green, blue: blue, alpha: 1.0).cgColor
  } else {
    return UIColor.black.cgColor
  }
}

现在将字符串数组映射到颜色数组

let hexColors = ["6909A1", "7552D1", "59B0DC", "62E3CC"]

let gradientColors = hexColors.map { color(from:$0) }

或UIColor扩展名

extension UIColor {

    convenience init(hexString : String)
    {
        if let rgbValue = UInt(hexString, radix: 16) {
            let red   =  CGFloat((rgbValue >> 16) & 0xff) / 255
            let green =  CGFloat((rgbValue >>  8) & 0xff) / 255
            let blue  =  CGFloat((rgbValue      ) & 0xff) / 255
            self.init(red: red, green: green, blue: blue, alpha: 1.0)
        } else {
            self.init(red: 0.0, green: 0.0, blue: 0.0, alpha: 1.0)
        }
    }
}

let hexColors = ["6909A1", "7552D1", "59B0DC", "62E3CC"]

let gradientColors = hexColors.map { UIColor(hexString:$0).cgColor }

Answer 2

不是太难，但是从十六进制字符串创建UIColor / CGColor对象的能力并没有内置到Swift中。但是，您可以将此扩展程序放入项目中以添加它：

extension UIColor {
    public convenience init?(hexString: String) {
        let r, g, b, a: CGFloat

        if hexString.hasPrefix("#") {
            let start = hexString.index(hexString.startIndex, offsetBy: 1)
            let hexColor = hexString.substring(from: start)

            if hexColor.characters.count == 8 {
                let scanner = Scanner(string: hexColor)
                var hexNumber: UInt64 = 0

                if scanner.scanHexInt64(&hexNumber) {
                    r = CGFloat((hexNumber & 0xff000000) >> 24) / 255
                    g = CGFloat((hexNumber & 0x00ff0000) >> 16) / 255
                    b = CGFloat((hexNumber & 0x0000ff00) >> 8) / 255
                    a = CGFloat(hexNumber & 0x000000ff) / 255

                    self.init(red: r, green: g, blue: b, alpha: a)
                    return
                }
            }
        }

        return nil
    }
}

然后你可以做这样的事情将十六进制颜色数组转换为CGColor数组：

func convertColours() {
    let stringColours = ["6909A1",
                         "7552D1",
                         "59B0DC",
                         "62E3CC"]
    var colours = [CGColor]()

    for stringColour in stringColours {
        if let colour = UIColor(hexString: stringColour) {
            colours.append(colour.cgColor)
        }
    }        
}

Answer 3

尝试这种方式

extension UIColor {
    convenience init(red: Int, green: Int, blue: Int) {
        self.init(red: CGFloat(red) / 255.0, green: CGFloat(green) / 255.0, blue: CGFloat(blue) / 255.0, alpha: 1.0)
    }

    func color(with hex: Int) -> CGColor {
        let color = UIColor(red:(hex >> 16) & 0xff, green:(hex >> 8) & 0xff, blue:hex & 0xff)
        return color.cgColor
    }
}
UIColor().color(with: Int(stringColours[0], radix: 16)!)
UIColor().color(with: 0x333333)

swift 3将字符串颜色转换为cgcolor

3 个答案: