为什么搜索栏未显示在tabbarcontroller中？

Question

我创建了一个包括搜索栏的homeviewController。当我的rootviewController为HomeViewController时，搜索栏看起来不错。但是，在我连接homeviewController与tabbarcontroller中的选项卡之后，我的搜索栏消失了。如果我只想在触摸该标签时显示它，该怎么办？

这就是我在homeviewController中所拥有的：

class HomeViewController: UICollectionViewController, UISearchBarDelegate {
    private let searchController = UISearchController(searchResultsController: nil)

    override func viewDidLoad() {
        super.viewDidLoad()
        setupSearchBar()
        }
    
    private func setupSearchBar(){
        definesPresentationContext = true
        navigationItem.searchController = self.searchController
        navigationItem.hidesSearchBarWhenScrolling = false
        searchController.searchBar.delegate = self
        let textFieldInsideSearchBar = searchController.searchBar.value(forKey: "searchField") as? UITextField
        textFieldInsideSearchBar?.textColor = .black
        textFieldInsideSearchBar?.placeholder = "position"
        ......
    }
}

这就是我在tabbarcontroller中所做的事情：

class TabBarController: UITabBarController {
    var homepage: HomeViewController?
    ......

    var subviewController: [UIViewController] = []
    override func viewDidLoad() {
        super.viewDidLoad()
        homepage = HomeViewController()
        ......

        subviewController.append(homepage!)
        ......

        homepage?.tabBarItem = UITabBarItem(title: "Home", image: UIImage(named: "home"), selectedImage: UIImage(named: "home-selected"))
        homepage?.tabBarItem.tag = 1
        ......
        self.setViewControllers(subviewController, animated: true)

        self.selectedIndex = 0
        self.selectedViewController = homepage
    }
}

这就是scendeelegate中的内容：

        guard let windowScene = (scene as? UIWindowScene) else{return}
            window = UIWindow(frame: windowScene.coordinateSpace.bounds)
            window?.windowScene = windowScene
            window?.rootViewController =
                    UINavigationController(rootViewController:
                    TabBarController())
            window?.makeKeyAndVisible()
        guard let _ = (scene as? UIWindowScene) else { return }

我是iOS的初学者。预先感谢任何人可以帮助我！