Swift 5 (Swift 4, Swift 3) UIColor扩展:

extension UIColor {
    convenience init(hexString: String) {
        let hex = hexString.trimmingCharacters(in: CharacterSet.alphanumerics.inverted)
        var int = UInt64()
        Scanner(string: hex).scanHexInt64(&int)
        let a, r, g, b: UInt64
        switch hex.count {
        case 3: // RGB (12-bit)
            (a, r, g, b) = (255, (int >> 8) * 17, (int >> 4 & 0xF) * 17, (int & 0xF) * 17)
        case 6: // RGB (24-bit)
            (a, r, g, b) = (255, int >> 16, int >> 8 & 0xFF, int & 0xFF)
        case 8: // ARGB (32-bit)
            (a, r, g, b) = (int >> 24, int >> 16 & 0xFF, int >> 8 & 0xFF, int & 0xFF)
        default:
            (a, r, g, b) = (255, 0, 0, 0)
        }
        self.init(red: CGFloat(r) / 255, green: CGFloat(g) / 255, blue: CGFloat(b) / 255, alpha: CGFloat(a) / 255)
    }
}

用法:

let darkGrey = UIColor(hexString: "#757575")

斯威夫特2。x版本:

extension UIColor {
    convenience init(hexString: String) {
        let hex = hexString.stringByTrimmingCharactersInSet(NSCharacterSet.alphanumericCharacterSet().invertedSet)
        var int = UInt32()
        NSScanner(string: hex).scanHexInt(&int)
        let a, r, g, b: UInt32
        switch hex.characters.count {
        case 3: // RGB (12-bit)
            (a, r, g, b) = (255, (int >> 8) * 17, (int >> 4 & 0xF) * 17, (int & 0xF) * 17)
        case 6: // RGB (24-bit)
            (a, r, g, b) = (255, int >> 16, int >> 8 & 0xFF, int & 0xFF)
        case 8: // ARGB (32-bit)
            (a, r, g, b) = (int >> 24, int >> 16 & 0xFF, int >> 8 & 0xFF, int & 0xFF)
        default:
            (a, r, g, b) = (255, 0, 0, 0)
        }
        self.init(red: CGFloat(r) / 255, green: CGFloat(g) / 255, blue: CGFloat(b) / 255, alpha: CGFloat(a) / 255)
    }
}

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

        if hex.hasPrefix("#") {
            let start = hex.index(hex.startIndex, offsetBy: 1)
            let hexColor = String(hex[start...])

            if hexColor.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
    }
}

用法:

let white = UIColor(hex: "#ffffff")

extension UIColor {

    convenience init(r: CGFloat, g: CGFloat, b: CGFloat, a: CGFloat = 1) {
        self.init(red: r/255, green: g/255, blue: b/255, alpha: a)
    }

    convenience init(hex: Int, alpha: CGFloat = 1) {
        self.init(r: CGFloat((hex >> 16) & 0xff), g: CGFloat((hex >> 08) & 0xff), b: CGFloat((hex >> 00) & 0xff), a: alpha)
    }
}

斯威夫特5

extension UIColor{

/// Converting hex string to UIColor
///
/// - Parameter hexString: input hex string
convenience init(hexString: String) {
    let hex = hexString.trimmingCharacters(in: CharacterSet.alphanumerics.inverted)
    var int = UInt64()
    Scanner(string: hex).scanHexInt64(&int)
    let a, r, g, b: UInt64
    switch hex.count {
    case 3:    
        (a, r, g, b) = (255, (int >> 8) * 17, (int >> 4 & 0xF) * 17, (int & 0xF) * 17)
    case 6: 
        (a, r, g, b) = (255, int >> 16, int >> 8 & 0xFF, int & 0xFF)
    case 8: 
        (a, r, g, b) = (int >> 24, int >> 16 & 0xFF, int >> 8 & 0xFF, int & 0xFF)
    default:
        (a, r, g, b) = (255, 0, 0, 0)
    }
    self.init(red: CGFloat(r) / 255, green: CGFloat(g) / 255, blue: CGFloat(b) / 255, alpha: CGFloat(a) / 255)
}
}

使用UIColor调用(hexString: "你的十六进制字符串")

这个答案展示了如何在Obj-C中实现。这座桥是要用的

let rgbValue = 0xFFEEDD
let r = Float((rgbValue & 0xFF0000) >> 16)/255.0
let g = Float((rgbValue & 0xFF00) >> 8)/255.0
let b = Float((rgbValue & 0xFF))/255.0
self.backgroundColor = UIColor(red:r, green: g, blue: b, alpha: 1.0)

用户界面颜色:

extension UIColor {

    convenience init(hex: Int) {
        let components = (
            R: CGFloat((hex >> 16) & 0xff) / 255,
            G: CGFloat((hex >> 08) & 0xff) / 255,
            B: CGFloat((hex >> 00) & 0xff) / 255
        )
        self.init(red: components.R, green: components.G, blue: components.B, alpha: 1)
    }

}

CGColor:

extension CGColor {

    class func colorWithHex(hex: Int) -> CGColorRef {

        return UIColor(hex: hex).CGColor

    }

}

使用

let purple = UIColor(hex: 0xAB47BC)