对我来说，在viewDidLoad（）方法中添加以下几行后，它起作用了：

searchController.hidesNavigationBarDuringPresentation = true navigationController?.navigationBar.prefersLargeTitles = true navigationController!.navigationBar.sizeToFit()

好的，所以我也一直试图为我的应用程序整天实现相同的目标，最终我做到了。

我想在UITableViewController上添加一个searchBar，我就是这样做的。

    let searchController: UISearchController = {

    let searchController = UISearchController(searchResultsController: nil)

    searchController.searchBar.placeholder = "New Search"
    searchController.searchBar.searchBarStyle = .minimal
    searchController.dimsBackgroundDuringPresentation = false
    searchController.definesPresentationContext = true

   return searchController
}()

首先使用闭包创建一个新的UISearchController，这样您就可以在代码中全局使用它，并在以后对其进行自定义。

然后在viewDidLoad中，设置searchSontroller.searchResultsUpdater = self和navigationItem.searchController = searchController。

对我来说，经过大量的试验和错误，它可以完美地工作，因为我是以编程方式进行所有操作的。

尝试一下，在我这边工作正常

    private var search = UISearchController(searchResultsController: nil)

    override func viewDidLoad() {
        super.viewDidLoad()
        search.searchBar.delegate = self
        search.searchBar.sizeToFit()
        search.obscuresBackgroundDuringPresentation = false
        search.hidesNavigationBarDuringPresentation = true
        self.definesPresentationContext = true
        search.searchBar.placeholder = "Search here"
        self.navigationItem.searchController = search
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        navigationItem.hidesSearchBarWhenScrolling = false
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        navigationItem.hidesSearchBarWhenScrolling = true
    }

对于大型导航栏，请使用此

要获得完整的应用程序导航栏支持，请在代码中添加此扩展名。

import UIKit
extension UIViewController {


    open func showNavigationBar(_ large: Bool,_ animated: Bool,titleColor: UIColor,barTintColor: UIColor,fontSize: CGFloat) {

        navigationController?.navigationBar.barTintColor = barTintColor
        navigationController?.navigationBar.backgroundColor = barTintColor
        navigationController?.navigationBar.isTranslucent = true
        self.navigationController?.setNavigationBarHidden(false,animated: animated)
        if large {
            self.navigationController?.navigationBar.prefersLargeTitles = true
            if #available(iOS 13.0,*) {
                let appearance = UINavigationBarAppearance()
                appearance.backgroundColor = barTintColor
                appearance.titleTextAttributes = [.foregroundColor: titleColor]
                appearance.largeTitleTextAttributes = [NSAttributedString.Key.foregroundColor: titleColor,NSAttributedString.Key.font: UIFont(resource: R.font.robotoMedium,size: fontSize)!]

                navigationController?.navigationBar.standardAppearance = appearance
                navigationController?.navigationBar.compactAppearance = appearance
                navigationController?.navigationBar.scrollEdgeAppearance = appearance
            } else {
                self.navigationController?.navigationBar.largeTitleTextAttributes = [NSAttributedString.Key.foregroundColor: titleColor,size: fontSize)!]
            }
        } else {
            self.navigationController?.navigationBar.prefersLargeTitles = false
            self.navigationController?.navigationBar.titleTextAttributes = [NSAttributedString.Key.foregroundColor: titleColor,size: 20.0)!]
        }
    }
}

然后简单地调用此方法

self.showNavigationBar(true,true,titleColor: UIColor.blue,barTintColor: UIColor.red,fontSize: 32.0)

如果然后还是不起作用，请使用此

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        search.searchBar.becomeFirstResponder()
    }

另一种解决方案是，在情节提要中添加一个高度为0的UIView，并在顶部设置具有安全区域的机顶盒，并在底部添加UIScrollView / UICollectionView / UITableVIew或其他可滚动视图，并删除TopSafeArea和ScrollableView Top之间的直接约束。我知道也许这不是解决方案，但我在情节提要中做了。

此代码应该有效

class NavigationController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()

        createCustomTabBar()
    }

    func createCustomTabBar() {
    
        let firstVC = UINavigationController(rootViewController: HomeVC())
        firstVC.title = "Home"
        firstVC.tabBarItem.image = UIImage(systemName: "house.fill")

        viewControllers = [firstVC]
    }

class HomeVC: UIViewController {
    let searchController = UISearchController(searchResultsController: nil)
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .white
        
        navigationController?.navigationBar.prefersLargeTitles = true
        navigationItem.title = "Home"
        navigationItem.searchController = searchController
    }
}