ios - swift 3 将字符串颜色转换为 cgcolor

Question

我是 swift 和 iOS 的新手，有些事情我不知道该怎么办。

我有来自后端的颜色，我想将其转换为 CGColor

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

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

从 JSON 转换后，我应该怎么做才能传递 CGColor 数组。我找不到正确的解决方案如何从简单的字符串中获取 CGColor

Answer 1

UInt 有一个方便的初始化程序，可以将十六进制字符串转换为其十六进制值

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) }

---

或者在 UIColor 扩展中

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 }