Swift 5, iOS 14

convenience init(hex: String, alpha: CGFloat = 1.0) {
    var hexFormatted: String = hex.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines).uppercased()
    
    if hexFormatted.hasPrefix("#") {
        hexFormatted = String(hexFormatted.dropFirst())
    }
    
    assert(hexFormatted.count == 6, "Invalid hex code used.")
    
    var rgbValue: UInt64 = 0
    Scanner(string: hexFormatted).scanHexInt64(&rgbValue)
    
    self.init(red: CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0,
              green: CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0,
              blue: CGFloat(rgbValue & 0x0000FF) / 255.0,
              alpha: alpha)
}

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

Swift等价于@Tom的答案，尽管接收RGBA Int值以支持透明度:

func colorWithHex(aHex: UInt) -> UIColor
{
    return UIColor(red: CGFloat((aHex & 0xFF000000) >> 24) / 255,
        green: CGFloat((aHex & 0x00FF0000) >> 16) / 255,
        blue: CGFloat((aHex & 0x0000FF00) >> 8) / 255,
        alpha: CGFloat((aHex & 0x000000FF) >> 0) / 255)
}

//usage
var color = colorWithHex(0x7F00FFFF)

如果你想从string中使用它，你可以使用strtoul:

var hexString = "0x7F00FFFF"

let num = strtoul(hexString, nil, 16)

var colorFromString = colorWithHex(num)

下面是Swift 1.2版本，作为UIColor的扩展。这允许你这样做

let redColor = UIColor(hex: "#FF0000")

我觉得这是最自然的做法。

extension UIColor {
  // Initialiser for strings of format '#_RED_GREEN_BLUE_'
  convenience init(hex: String) {
    let redRange    = Range<String.Index>(start: hex.startIndex.advancedBy(1), end: hex.startIndex.advancedBy(3))
    let greenRange  = Range<String.Index>(start: hex.startIndex.advancedBy(3), end: hex.startIndex.advancedBy(5))
    let blueRange   = Range<String.Index>(start: hex.startIndex.advancedBy(5), end: hex.startIndex.advancedBy(7))

    var red     : UInt32 = 0
    var green   : UInt32 = 0
    var blue    : UInt32 = 0

    NSScanner(string: hex.substringWithRange(redRange)).scanHexInt(&red)
    NSScanner(string: hex.substringWithRange(greenRange)).scanHexInt(&green)
    NSScanner(string: hex.substringWithRange(blueRange)).scanHexInt(&blue)

    self.init(
      red: CGFloat(red) / 255,
      green: CGFloat(green) / 255,
      blue: CGFloat(blue) / 255,
      alpha: 1
    )
  }
}

斯威夫特版本:

extension UIColor {
    convenience init?(var hex: String) {
        hex = hex.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).uppercaseString
        hex = (hex.hasPrefix("#")) ? hex.substringFromIndex(advance(hex.startIndex, 1)) : hex

        var value: UInt32 = 0
        if NSScanner(string: hex).scanHexInt(&value) {
            if count(hex) == 8 {
                self.init(red: CGFloat((value & 0xFF000000) >> 24) / 255.0,
                    green: CGFloat((value & 0x00FF0000) >> 16) / 255.0,
                    blue: CGFloat((value & 0x0000FF00) >> 8) / 255.0,
                    alpha: CGFloat((value & 0x000000FF)) / 255.0)
                return
            } else if count(hex) == 6 {
                self.init(red: CGFloat((value & 0xFF0000) >> 16) / 255.0,
                    green: CGFloat((value & 0x00FF00) >> 8) / 255.0,
                    blue: CGFloat(value & 0x0000FF) / 255.0,
                    alpha: 1.0)
                return
            }
        }
        self.init()
        return nil
    }
}

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