添加糢糊视图

override func viewDidLoad() {
        super.viewDidLoad()

        //糢糊效果类
        var blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Light)

        //糢糊效果视图类
        var blurView = UIVisualEffectView(effect: blurEffect)

        //设置糢糊视图的显示大小，与屏幕大小一致
        blurView.frame = UIScreen.mainScreen().bounds

        //将糢糊视图添加到view中
        self.view.addSubview(blurView)
    }