// 1.设置导航栏标题属性：设置标题颜色        self.navigationController?.navigationBar.titleTextAttributes = [NSForegroundColorAttributeName:UIColor.white]        // 2.设置导航栏前景色：设置item指示色        self.navigationController?.navigationBar.tintColor = UIColor.purple                // 3.设置导航栏半透明        self.navigationController?.navigationBar.isTranslucent = true                // 4.设置导航栏背景图片        self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: UIBarMetrics.default)                // 5.设置导航栏阴影图片        self.navigationController?.navigationBar.shadowImage = UIImage()