如何在Swift 5中以编程方式更改导航栏的背景颜色？

func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
    let navBar = navigationController.navigationBar
    navBar.barTintColor = UIColor.red // 设置导航栏背景颜色
    navBar.tintColor = UIColor.white // 设置导航栏按钮颜色
    navBar.titleTextAttributes = [NSAttributedString.Key.foregroundColor: UIColor.white] // 设置导航栏标题颜色
}

func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
    let navBar = navigationController.navigationBar
    let backgroundImage = UIImage(named: "nav_background")
    navBar.setBackgroundImage(backgroundImage, for: .default)
    navBar.tintColor = UIColor.white
    navBar.titleTextAttributes = [NSAttributedString.Key.foregroundColor: UIColor.white]
}