Swift 16进制转颜色

extension UIColor{

class func colorWithHexString(hex:String,alpha:CGFloat) -> UIColor {

var cString = hex.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines).uppercased()

if cString.hasPrefix("#") {

let index = cString.index(after: cString.startIndex)

cString = cString.substring(from: index)

}

if cString.characters.count != 6 {

return UIColor.black

}

let rRange = cString.startIndex ..< cString.index(cString.startIndex, offsetBy: 2)

let rString = cString.substring(with: rRange)

print(rString);

let gRange = cString.index(cString.startIndex, offsetBy: 2) ..< cString.index(cString.startIndex, offsetBy: 4)

let gString = cString.substring(with: gRange)

print(gString);

let bRange = cString.index(cString.startIndex, offsetBy: 4) ..< cString.index(cString.startIndex, offsetBy: 6)

let bString = cString.substring(with: bRange)

print(bString);

var r:CUnsignedInt = 0, g:CUnsignedInt = 0, b:CUnsignedInt = 0

Scanner(string: rString).scanHexInt32(&r)

Scanner(string: gString).scanHexInt32(&g)

Scanner(string: bString).scanHexInt32(&b)

return UIColor(red: CGFloat(r)/255.0, green: CGFloat(g)/255.0, blue: CGFloat(b)/255.0, alpha: alpha)

}

}