我做了一个小函数，把它放在我可以全局使用它的地方，在swift 2.1中工作得很好:

func getColorFromHex(rgbValue:UInt32)->UIColor{
   let red = CGFloat((rgbValue & 0xFF0000) >> 16)/255.0
   let green = CGFloat((rgbValue & 0xFF00) >> 8)/255.0
   let blue = CGFloat(rgbValue & 0xFF)/255.0

   return UIColor(red:red, green:green, blue:blue, alpha:1.0)
}

用法:

getColorFromHex(0xffffff)

extension UIColor {

      convenience init(hex: Int, alpha: Double = 1.0) {

      self.init(red: CGFloat((hex>>16)&0xFF)/255.0, green:CGFloat((hex>>8)&0xFF)/255.0, blue: CGFloat((hex)&0xFF)/255.0, alpha:  CGFloat(255 * alpha) / 255)
     }
}

使用这个扩展像:

let selectedColor = UIColor(hex: 0xFFFFFF)
let selectedColor = UIColor(hex: 0xFFFFFF, alpha: 0.5)

斯威夫特4.0

使用这种单行方法

override func viewDidLoad() {
    super.viewDidLoad()

   let color = UIColor(hexColor: "FF00A0")
   self.view.backgroundColor = color

}

你必须创建新的类或使用任何控制器，你需要使用十六进制颜色。这个扩展类为您提供UIColor，将十六进制转换为RGB颜色。

extension UIColor {
convenience init(hexColor: String) {
    let scannHex = Scanner(string: hexColor)
    var rgbValue: UInt64 = 0
    scannHex.scanLocation = 0
    scannHex.scanHexInt64(&rgbValue)
    let r = (rgbValue & 0xff0000) >> 16
    let g = (rgbValue & 0xff00) >> 8
    let b = rgbValue & 0xff
    self.init(
        red: CGFloat(r) / 0xff,
        green: CGFloat(g) / 0xff,
        blue: CGFloat(b) / 0xff, alpha: 1
    )
  }
}

另一种方法

斯威夫特3.0

为UIColor写一个扩展

// To change the HexaDecimal value to Corresponding Color
extension UIColor
{
    class func uicolorFromHex(_ rgbValue:UInt32, alpha : CGFloat)->UIColor

    {
        let red = CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0
        let green = CGFloat((rgbValue & 0xFF00) >> 8) / 255.0
        let blue = CGFloat(rgbValue & 0xFF) / 255.0
        return UIColor(red:red, green:green, blue:blue, alpha: alpha)
    }
}

你可以像这样用hex直接创建UIColor

let carrot = UIColor.uicolorFromHex(0xe67e22, alpha: 1))

斯威夫特2.0:

在viewDidLoad ()

 var viewColor:UIColor
    viewColor = UIColor()
    let colorInt:UInt
    colorInt = 0x000000
    viewColor = UIColorFromRGB(colorInt)
    self.View.backgroundColor=viewColor



func UIColorFromRGB(rgbValue: UInt) -> UIColor {
    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)
    )
}

我从这个回答中总结了一些想法，并针对iOS 13和Swift 5进行了更新。

extension UIColor {
  
  convenience init(_ hex: String, alpha: CGFloat = 1.0) {
    var cString = hex.trimmingCharacters(in: .whitespacesAndNewlines).uppercased()
    
    if cString.hasPrefix("#") { cString.removeFirst() }
    
    if cString.count != 6 {
      self.init("ff0000") // return red color for wrong hex input
      return
    }
    
    var rgbValue: UInt64 = 0
    Scanner(string: cString).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)
  }

}

然后你可以这样使用它:

UIColor("#ff0000") // with #
UIColor("ff0000")  // without #
UIColor("ff0000", alpha: 0.5) // using optional alpha value