swift - 更改导航项标题

Question

我正在尝试更改 Product 中的标题，但不知何故 navigationItem 有所不同。为什么 Container 中的 navigationItem 与 Product 中的不一样？

class VC1: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let controller = Container()
        let navigation = UINavigationController(rootViewController: controller)

        navigationController?.pushViewController(navigation, animated: true)
    }
}

class Container: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        print(navigationItem)
        navigationItem.title = "test"

        let controller = Product()

        controller.didMove(toParentViewController: self)
        self.addChildViewController(controller)

        view.addSubview(controller.view)
    }
}

class Product: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        print(navigationItem)
        navigationItem.title = "" // Doesn't remove the title
    }
}

Answer 1

我正在阅读 navigationItem 的文档，它是这样说的:

This is a unique instance of UINavigationItem created to represent the view controller when it is pushed onto a navigation controller.

但是，在您的情况下，嵌入式 VC 不是导航 Controller 的直接子级。

所以，我尝试了以下代码并且它有效。关键部分是，如果存在父 View Controller ，我会重写 navigationItem 以返回父级的导航项。

override var navigationItem: UINavigationItem {
    if let parentItem = parent?.navigationItem {
        return parentItem
    } else {
        return super.navigationItem
    }
}