extension UIColor {
    convenience init(hexaString: String, alpha: CGFloat = 1) {
        let chars = Array(hexaString.dropFirst())
        self.init(red:   .init(strtoul(String(chars[0...1]),nil,16))/255,
                  green: .init(strtoul(String(chars[2...3]),nil,16))/255,
                  blue:  .init(strtoul(String(chars[4...5]),nil,16))/255,
                  alpha: alpha)}
}

用法:

let redColor       = UIColor(hexaString: "#FF0000")              // r 1,0 g 0,0 b 0,0 a 1,0
let transparentRed = UIColor(hexaString: "#FF0000", alpha: 0.5)  // r 1,0 g 0,0 b 0,0 a 0,5

另一种选择是将六值转换为无符号整数，并从中提取相应的值:

extension UIColor {
    convenience init(hexaString: String, alpha: CGFloat = 1) {
        self.init(hexa: UInt(hexaString.dropFirst(), radix: 16) ?? 0, alpha: alpha)
    }
    convenience init(hexa: UInt, alpha: CGFloat = 1) {
        self.init(red:   .init((hexa & 0xff0000) >> 16) / 255,
                  green: .init((hexa & 0xff00  ) >>  8) / 255,
                  blue:  .init( hexa & 0xff    )        / 255,
                  alpha: alpha)
    }
}

let purpleColor       = UIColor(hexaString: "#FF00FF")    // r 1,0 g 0,0 b 1,0 a 1,0
let transparentYellow = UIColor(hexaString: "#FFFF00", alpha: 0.5)  // r 1,0 g 1,0 b 0,0 a 0,5

上面的几个解决方案涉及到一些不必要的nsstring使用。这个UIColor类扩展更简单更快:

+ colorWithHex:(UInt32)hex alpha:(CGFloat)alpha
{
    return [UIColor colorWithRed:((hex & 0xFF0000) >> 16)/255.0
                           green:((hex & 0x00FF00) >> 8)/255.0
                            blue:( hex & 0x0000FF)/255.0
                           alpha:alpha];
}

简单来说:

return [UIColor colorWithHex:0x006400 alpha:1.0]; // HTML darkgreen

伊森·斯特里德回答的简单例子。一个接受十六进制字符串并返回UIColor的函数。 (你可以输入十六进制字符串格式:#ffffff或ffffff)

例子:

func hexStringToUIColor (hex:String) -> UIColor {
    var cString: String = hex.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines).uppercased()

    if (cString.hasPrefix("#")) {
        if let range = cString.range(of: cString) {
            cString = cString.substring(from: cString.index(range.lowerBound, offsetBy: 1))
        }
    }

    if ((cString.characters.count) != 6) {
        return UIColor.gray
    }

    var rgbValue: UInt32 = 0
    Scanner(string: cString).scanHexInt32(&rgbValue)

    return UIColor(
        red: CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0,
        green: CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0,
        blue: CGFloat(rgbValue & 0x0000FF) / 255.0,
        alpha: CGFloat(1.0)
    )
}

用法:

var color1 = hexStringToUIColor("#d3d3d3")

这是另一种选择。

- (UIColor *)colorWithRGBHex:(UInt32)hex
{
    int r = (hex >> 16) & 0xFF;
    int g = (hex >> 8) & 0xFF;
    int b = (hex) & 0xFF;

    return [UIColor colorWithRed:r / 255.0f
                           green:g / 255.0f
                            blue:b / 255.0f
                           alpha:1.0f];
}

一个伟大的Swift实现(为Xcode 7更新)使用扩展，从各种不同的答案和地方拉到一起。在结尾还需要字符串扩展名。

Use:

let hexColor = UIColor(hex: "#00FF00")

注意:我添加了一个选项，为alpha通道的标准6位十六进制值的末尾添加2个额外的数字(传入值为00-99)。如果这冒犯了你，就把它拿掉。您可以实现它来传递一个可选的alpha参数。

扩展:

extension UIColor {

    convenience init(var hex: String) {
        var alpha: Float = 100
        let hexLength = hex.characters.count
        if !(hexLength == 7 || hexLength == 9) {
            // A hex must be either 7 or 9 characters (#RRGGBBAA)
            print("improper call to 'colorFromHex', hex length must be 7 or 9 chars (#GGRRBBAA)")
            self.init(white: 0, alpha: 1)
            return
        }

        if hexLength == 9 {
            // Note: this uses String subscripts as given below
            alpha = hex[7...8].floatValue
            hex = hex[0...6]
        }

        // Establishing the rgb color
        var rgb: UInt32 = 0
        let s: NSScanner = NSScanner(string: hex)
        // Setting the scan location to ignore the leading `#`
        s.scanLocation = 1
        // Scanning the int into the rgb colors
        s.scanHexInt(&rgb)

        // Creating the UIColor from hex int
        self.init(
            red: CGFloat((rgb & 0xFF0000) >> 16) / 255.0,
            green: CGFloat((rgb & 0x00FF00) >> 8) / 255.0,
            blue: CGFloat(rgb & 0x0000FF) / 255.0,
            alpha: CGFloat(alpha / 100)
        )
    }
}

字符串扩展: 浮动的来源 下标源

extension String {

    /**
    Returns the float value of a string
    */
    var floatValue: Float {
        return (self as NSString).floatValue
    }

    /**
    Subscript to allow for quick String substrings ["Hello"][0...1] = "He"
    */
    subscript (r: Range<Int>) -> String {
        get {
            let start = self.startIndex.advancedBy(r.startIndex)
            let end = self.startIndex.advancedBy(r.endIndex - 1)
            return self.substringWithRange(start..<end)
        }
    }
}

有一个很好的帖子是关于如何解决OP的问题，从十六进制字符串中提取UIColor。下面给出的解决方案与其他解决方案不同，因为它支持字符串值，可能包括'0x'或'#'前缀的十六进制字符串表示…(请参阅使用)

这是主要的部分…

- (UIColor *)getUIColorObjectFromHexString:(NSString *)hexStr alpha:(CGFloat)alpha
{
  // Convert hex string to an integer
  unsigned int hexint = [self intFromHexString:hexStr];
 
  // Create a color object, specifying alpha as well
  UIColor *color =
    [UIColor colorWithRed:((CGFloat) ((hexint & 0xFF0000) >> 16))/255
    green:((CGFloat) ((hexint & 0xFF00) >> 8))/255
    blue:((CGFloat) (hexint & 0xFF))/255
    alpha:alpha];
 
  return color;
}

助手方法……

- (unsigned int)intFromHexString:(NSString *)hexStr
{
  unsigned int hexInt = 0;
 
  // Create scanner
  NSScanner *scanner = [NSScanner scannerWithString:hexStr];
 
  // Tell scanner to skip the # character
  [scanner setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"#"]];
 
  // Scan hex value
  [scanner scanHexInt:&hexInt];
 
  return hexInt;
}

用法:

NSString *hexStr1 = @"123ABC";
NSString *hexStr2 = @"#123ABC";
NSString *hexStr3 = @"0x123ABC";

UIColor *color1 = [self getUIColorObjectFromHexString:hexStr1 alpha:.9];
NSLog(@"UIColor: %@", color1);
 
UIColor *color2 = [self getUIColorObjectFromHexString:hexStr2 alpha:.9];
NSLog(@"UIColor: %@", color2);
 
UIColor *color3 = [self getUIColorObjectFromHexString:hexStr3 alpha:.9];
NSLog(@"UIColor: %@", color3);

完整的参考文章

Swift 2 +

我已经将这个解决方案移植到Swift 2.2。注意，我已经将alpha参数更改为使用默认设置为1.0。我还根据Swift 2.2中的NSScanner类的要求将int类型更新为UInt32。

func colorWithHexString(hexString: String, alpha:CGFloat = 1.0) -> UIColor {
    
    // Convert hex string to an integer
    let hexint = Int(self.intFromHexString(hexString))
    let red = CGFloat((hexint & 0xff0000) >> 16) / 255.0
    let green = CGFloat((hexint & 0xff00) >> 8) / 255.0
    let blue = CGFloat((hexint & 0xff) >> 0) / 255.0 
    
    // Create color object, specifying alpha as well
    let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)
    return color
}

func intFromHexString(hexStr: String) -> UInt32 {
    var hexInt: UInt32 = 0
    // Create scanner
    let scanner: NSScanner = NSScanner(string: hexStr)
    // Tell scanner to skip the # character
    scanner.charactersToBeSkipped = NSCharacterSet(charactersInString: "#")
    // Scan hex value
    scanner.scanHexInt(&hexInt)
    return hexInt
}

斯威夫特 4+

采用与swift 4相同的变化逻辑，

func colorWithHexString(hexString: String, alpha:CGFloat = 1.0) -> UIColor {
    
    // Convert hex string to an integer
    let hexint = Int(self.intFromHexString(hexStr: hexString))
    let red = CGFloat((hexint & 0xff0000) >> 16) / 255.0
    let green = CGFloat((hexint & 0xff00) >> 8) / 255.0
    let blue = CGFloat((hexint & 0xff) >> 0) / 255.0
    
    // Create color object, specifying alpha as well
    let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)
    return color
}

func intFromHexString(hexStr: String) -> UInt32 {
    var hexInt: UInt32 = 0
    // Create scanner
    let scanner: Scanner = Scanner(string: hexStr)
    // Tell scanner to skip the # character
    scanner.charactersToBeSkipped = CharacterSet(charactersIn: "#")
    // Scan hex value
    scanner.scanHexInt32(&hexInt)
    return hexInt
}

Swift 5 (iOS 13)+

下面显示了在SDK弃用scanHexInt32的情况下工作的更新。我将代码封装到Swift playground文件中。

//: A UIKit based Playground for presenting user interface
  
import UIKit
import PlaygroundSupport

class MyViewController : UIViewController {
    override func loadView() {
        let view = UIView()
        view.backgroundColor = .white

        let label = UILabel()
        label.frame = CGRect(x: 150, y: 200, width: 200, height: 20)
        label.text = "Hello World!"
        label.textColor = colorWithHexString(hexString: "22F728")
        
        view.addSubview(label)
        self.view = view
    }
    
    func colorWithHexString(hexString: String, alpha:CGFloat = 1.0) -> UIColor {

        // Convert hex string to an integer
        let hexint = Int(self.intFromHexString(hexStr: hexString))
        let red = CGFloat((hexint & 0xff0000) >> 16) / 255.0
        let green = CGFloat((hexint & 0xff00) >> 8) / 255.0
        let blue = CGFloat((hexint & 0xff) >> 0) / 255.0

        // Create color object, specifying alpha as well
        let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)
        return color
    }

    func intFromHexString(hexStr: String) -> UInt32 {
        var hexInt: UInt32 = 0
        // Create scanner
        let scanner: Scanner = Scanner(string: hexStr)
        // Tell scanner to skip the # character
        scanner.charactersToBeSkipped = CharacterSet(charactersIn: "#")
        // Scan hex value
        hexInt = UInt32(bitPattern: scanner.scanInt32(representation: .hexadecimal) ?? 0)
        return hexInt
    }
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()

彩色十六进制参考 HTML颜色名称和代码 十六进制颜色编码