//設置導航欄透明  func setNavigationIsTranslucent(isTranslucent:Bool) {    if isTranslucent == true {      self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)      self.navigationController?.navigationBar.shadowImage = UIImage()      navigationController?.navigationBar.barStyle = .black    }else {      navigationController?.navigationBar.setBackgroundImage(UIImage(named: "nav_bg"), for: .default)      navigationController?.navigationBar.shadowImage = UIImage()      navigationController?.navigationBar.barStyle = .black    }  }