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)
}

你可以创建UIColor的扩展类:-

扩展UIColor {

// MARK: - getColorFromHex ／** 此函数将颜色十六进制代码转换为RGB。

- parameter color  hex string.

- returns: RGB color code.
*/
class func getColorFromHex(hexString:String)->UIColor{

    var rgbValue : UInt32 = 0
    let scanner:NSScanner =  NSScanner(string: hexString)

    scanner.scanLocation = 1
    scanner.scanHexInt(&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))
}

}

为UIColor创建优雅的扩展:

extension UIColor {

convenience init(string: String) {

        var uppercasedString = string.uppercased()
        uppercasedString.remove(at: string.startIndex)

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

        let red = CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0
        let green = CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0
        let blue = CGFloat(rgbValue & 0x0000FF) / 255.0

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

创建红色:

let red = UIColor(string: "#ff0000") 

我已经找到了一个与Android使用的十六进制格式字符串100%兼容的解决方案，我发现这在进行跨平台移动开发时非常有用。它让我在两个平台上都使用一种颜色。您可以在没有归属的情况下随意重用，如果您愿意，也可以在Apache许可下重用。

#import "UIColor+HexString.h"

@interface UIColor(HexString)

+ (UIColor *) colorWithHexString: (NSString *) hexString;
+ (CGFloat) colorComponentFrom: (NSString *) string start: (NSUInteger) start length: (NSUInteger) length;

@end


@implementation UIColor(HexString)

+ (UIColor *) colorWithHexString: (NSString *) hexString {
    NSString *colorString = [[hexString stringByReplacingOccurrencesOfString: @"#" withString: @""] uppercaseString];
    CGFloat alpha, red, blue, green;
    switch ([colorString length]) {
        case 3: // #RGB
            alpha = 1.0f;
            red   = [self colorComponentFrom: colorString start: 0 length: 1];
            green = [self colorComponentFrom: colorString start: 1 length: 1];
            blue  = [self colorComponentFrom: colorString start: 2 length: 1];
            break;
        case 4: // #ARGB
            alpha = [self colorComponentFrom: colorString start: 0 length: 1];
            red   = [self colorComponentFrom: colorString start: 1 length: 1];
            green = [self colorComponentFrom: colorString start: 2 length: 1];
            blue  = [self colorComponentFrom: colorString start: 3 length: 1];          
            break;
        case 6: // #RRGGBB
            alpha = 1.0f;
            red   = [self colorComponentFrom: colorString start: 0 length: 2];
            green = [self colorComponentFrom: colorString start: 2 length: 2];
            blue  = [self colorComponentFrom: colorString start: 4 length: 2];                      
            break;
        case 8: // #AARRGGBB
            alpha = [self colorComponentFrom: colorString start: 0 length: 2];
            red   = [self colorComponentFrom: colorString start: 2 length: 2];
            green = [self colorComponentFrom: colorString start: 4 length: 2];
            blue  = [self colorComponentFrom: colorString start: 6 length: 2];                      
            break;
        default:
            [NSException raise:@"Invalid color value" format: @"Color value %@ is invalid.  It should be a hex value of the form #RBG, #ARGB, #RRGGBB, or #AARRGGBB", hexString];
            break;
    }
    return [UIColor colorWithRed: red green: green blue: blue alpha: alpha];
}

+ (CGFloat) colorComponentFrom: (NSString *) string start: (NSUInteger) start length: (NSUInteger) length {
    NSString *substring = [string substringWithRange: NSMakeRange(start, length)];
    NSString *fullHex = length == 2 ? substring : [NSString stringWithFormat: @"%@%@", substring, substring];
    unsigned hexComponent;
    [[NSScanner scannerWithString: fullHex] scanHexInt: &hexComponent];
    return hexComponent / 255.0;
}

@end 

迅速:

extension UIColor {
    convenience init?(hexString: String?) {
        let input: String! = (hexString ?? "")
            .replacingOccurrences(of: "#", with: "")
            .uppercased()
        var alpha: CGFloat = 1.0
        var red: CGFloat = 0
        var blue: CGFloat = 0
        var green: CGFloat = 0
        switch (input.count) {
        case 3 /* #RGB */:
            red = Self.colorComponent(from: input, start: 0, length: 1)
            green = Self.colorComponent(from: input, start: 1, length: 1)
            blue = Self.colorComponent(from: input, start: 2, length: 1)
            break
        case 4 /* #ARGB */:
            alpha = Self.colorComponent(from: input, start: 0, length: 1)
            red = Self.colorComponent(from: input, start: 1, length: 1)
            green = Self.colorComponent(from: input, start: 2, length: 1)
            blue = Self.colorComponent(from: input, start: 3, length: 1)
            break
        case 6 /* #RRGGBB */:
            red = Self.colorComponent(from: input, start: 0, length: 2)
            green = Self.colorComponent(from: input, start: 2, length: 2)
            blue = Self.colorComponent(from: input, start: 4, length: 2)
            break
        case 8 /* #AARRGGBB */:
            alpha = Self.colorComponent(from: input, start: 0, length: 2)
            red = Self.colorComponent(from: input, start: 2, length: 2)
            green = Self.colorComponent(from: input, start: 4, length: 2)
            blue = Self.colorComponent(from: input, start: 6, length: 2)
            break
        default:
            NSException.raise(NSExceptionName("Invalid color value"), format: "Color value \"%@\" is invalid.  It should be a hex value of the form #RBG, #ARGB, #RRGGBB, or #AARRGGBB", arguments:getVaList([hexString ?? ""]))
        }
        self.init(red: red, green: green, blue: blue, alpha: alpha)
    }
    
    static func colorComponent(from string: String!, start: Int, length: Int) -> CGFloat {
        let substring = (string as NSString)
            .substring(with: NSRange(location: start, length: length))
        let fullHex = length == 2 ? substring : "\(substring)\(substring)"
        var hexComponent: UInt64 = 0
        Scanner(string: fullHex)
            .scanHexInt64(&hexComponent)
        return CGFloat(Double(hexComponent) / 255.0)
    }
}

一个简明的解决方案:

// Assumes input like "#00FF00" (#RRGGBB).
+ (UIColor *)colorFromHexString:(NSString *)hexString {
    unsigned rgbValue = 0;
    NSScanner *scanner = [NSScanner scannerWithString:hexString];
    [scanner setScanLocation:1]; // bypass '#' character
    [scanner scanHexInt:&rgbValue];
    return [UIColor colorWithRed:((rgbValue & 0xFF0000) >> 16)/255.0 green:((rgbValue & 0xFF00) >> 8)/255.0 blue:(rgbValue & 0xFF)/255.0 alpha:1.0];
}

Swift 2.0版本的解决方案，将处理alpha值的颜色和完美的错误处理:

func RGBColor(hexColorStr : String) -> UIColor?{

    var red:CGFloat = 0.0
    var green:CGFloat = 0.0
    var blue:CGFloat = 0.0
    var alpha:CGFloat = 1.0

    if hexColorStr.hasPrefix("#"){

        let index   = hexColorStr.startIndex.advancedBy(1)
        let hex     = hexColorStr.substringFromIndex(index)
        let scanner = NSScanner(string: hex)
        var hexValue: CUnsignedLongLong = 0

        if scanner.scanHexLongLong(&hexValue)
        {
            if hex.characters.count == 6
            {
                red   = CGFloat((hexValue & 0xFF0000) >> 16) / 255.0
                green = CGFloat((hexValue & 0x00FF00) >> 8)  / 255.0
                blue  = CGFloat(hexValue & 0x0000FF) / 255.0
            }
            else if hex.characters.count == 8
            {
                red   = CGFloat((hexValue & 0xFF000000) >> 24) / 255.0
                green = CGFloat((hexValue & 0x00FF0000) >> 16) / 255.0
                blue  = CGFloat((hexValue & 0x0000FF00) >> 8)  / 255.0
                alpha = CGFloat(hexValue & 0x000000FF)         / 255.0
            }
            else
            {
                print("invalid hex code string, length should be 7 or 9", terminator: "")
                return nil
            }
        }
        else
        {
            print("scan hex error")
       return nil
        }
    }

    let color: UIColor =  UIColor(red:CGFloat(red), green: CGFloat(green), blue:CGFloat(blue), alpha: alpha)
    return color
}