分享一個很簡單的讓系統的導航欄透明的懸浮在ViewController上效果，就幾行程式碼！

class SomeViewController : UIViewController {
    ...
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
//        self.edgesForExtendedLayout = .All      // 要設定成全屏佈局才能看到效果，預設就是全屏的
//        self.navigationController?.navigationBar.translucent = true // 必須開啟半透明效果，預設就是開啟的
        let clearImage = UIImage.colorImage(UIColor.clearColor())   // 建立一個透明的圖片
        self.navigationController?.navigationBar.setBackgroundImage(clearImage, forBarMetrics: .Default)
        self.navigationController?.navigationBar.shadowImage = clearImage
    }
    ...
}
 

//MARK:- 建立一個顏色圖片
extension UIImage {
    class func colorImage(color: UIColor) -> UIImage {
        return self.colorImage(color, size: CGSize(width: 2, height: 2))
    }
    class func colorImage(color: UIColor, size: CGSize) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(size, false, 0)
        color.setFill()
        UIRectFillUsingBlendMode(CGRectMake(0, 0, size.width, size.height), kCGBlendModeXOR)
        let cgImage = CGBitmapContextCreateImage(UIGraphicsGetCurrentContext())
        UIGraphicsEndImageContext()
        return UIImage(CGImage: cgImage)!.stretchableImageWithLeftCapWidth(1, topCapHeight: 1)
    }
}