自定义UINavigationController标题不会显示在子视图中

Question

我已经创建了一个自定义UINavigationController类来轻松设置我应用的导航栏。

class NavigationController: UINavigationController {
    override func viewDidLoad() {
        super.viewDidLoad()
        configureNavigationBar()
    }
}

extension NavigationController {
    func configureNavigationBar() {
        navigationBar.tintColor = UIColor.white
        navigationBar.backgroundColor = UIColor.clear
        navigationBar.isTranslucent = false
        navigationBar.barStyle = .black
        navigationBar.setBackgroundImage(UIImage(), for: .default)
        navigationBar.shadowImage = UIImage()

        let attributes = [NSForegroundColorAttributeName: UIColor.white, NSFontAttributeName: UIFont(name: "Merriweather-Bold", size:17)!]
        navigationBar.titleTextAttributes = attributes

        let gradientLayer = CAGradientLayer()
        let topColor:UIColor = UIColor(hex: 0xf91e4e)
        let bottomColor:UIColor = UIColor(hex: 0xcc4d7f)
        gradientLayer.colors = [bottomColor.cgColor, topColor.cgColor]
        gradientLayer.startPoint = CGPoint(x: 0.0, y: 1.0)
        gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.0)
        gradientLayer.frame = CGRect(x: 0, y: -20, width: navigationBar.frame.size.width, height: navigationBar.frame.size.height + 20)
        navigationBar.layer.insertSublayer(gradientLayer, at: 0)

        UIApplication.shared.statusBarStyle = .lightContent
    }
}

它在root viewControllers中运行良好。

但导航栏的标题并没有详细显示VC。

到目前为止，我已尝试过这些解决方案，但这些解决方案都不起作用;

navigationItem.title = "Test"

2：

self.title = "Test"

3：

navigationController?.navigationBar.topItem?.title = "TEST" // This changes first viewController’s title

4：

navigationController?.navigationItem.title = "TEST"