UINavigationBar Large Title doesn't appear when scroll view up

Question

I have implemented a feature, when you press on a UITabBar icon and viewController1 scrolls up using its UIScrollView. It works perfectly, but if I scroll view down and stop somewhere, then switch to another viewController2, then get back to viewController1 and press tabBar icon - the viewController1 will scroll up, but Large Title will never be showed, and I should press tabBar icon one more time to show it:

The code I use for scroll up the VC1:

private var biggestTopSafeAreaInset: CGFloat = 0

    override func viewSafeAreaInsetsDidChange() {
        super.viewSafeAreaInsetsDidChange()
        self.biggestTopSafeAreaInset = max(view.safeAreaInsets.top, biggestTopSafeAreaInset)
    }
    
    func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
        if tabBarController.selectedIndex == 0 {
            let navigationVC = viewController as? UINavigationController
            let firstVC = navigationVC?.viewControllers.first as? CurrencyViewController
            guard let scrollView = firstVC?.view.subviews.first(where: { $0 is UIScrollView }) as? UIScrollView else { return }
            
            if traitCollection.verticalSizeClass == .compact {
                scrollView.setContentOffset(CGPoint(x: 0, y: -view.safeAreaInsets.top, animated: true)
            } else {
                scrollView.setContentOffset(CGPoint(x: 0, y: -biggestTopSafeAreaInset, animated: true)
            }
        }
    }

I tried to track biggestTopSafeAreaInset in different stages of VC1 life, but it always has the same number - 196.0. But then why it doesn't scroll till the Large Title after viewControllers switch?

Answer 1

in your tableView set contentInsetAdjustmentBehavior to never

tableView.contentInsetAdjustmentBehavior = .never

in controller update the ui of navigation bar again

  override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        DispatchQueue.main.async { [weak self] in
            self?.navigationController?.navigationBar.sizeToFit()
        }
       
    }

here is the navigation controller

class BaseNavigationController: UINavigationController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        if #available(iOS 15.0, *) {
            let scrollAppearance = UINavigationBarAppearance()
            scrollAppearance.shadowColor = .white
            scrollAppearance.backgroundColor = .white
            let navigationBarAppearance = UINavigationBarAppearance()
            navigationBarAppearance.configureWithDefaultBackground()
            navigationBarAppearance.backgroundColor = .white
            navigationBarAppearance.largeTitleTextAttributes = [
                NSAttributedString.Key.font: UIFont.systemFont(ofSize: 26),
                NSAttributedString.Key.foregroundColor: UIColor.black
            ]
            navigationBarAppearance.titleTextAttributes = [
                NSAttributedString.Key.font: UIFont.systemFont(ofSize: 17),
                NSAttributedString.Key.foregroundColor: UIColor.black
            ]
            UINavigationBar.appearance().backIndicatorImage = UIImage(named: "back-arrow")
            UINavigationBar.appearance().standardAppearance = navigationBarAppearance
            UINavigationBar.appearance().compactAppearance = navigationBarAppearance
            UINavigationBar.appearance().scrollEdgeAppearance = scrollAppearance
            navigationBar.tintColor = .black
            navigationBar.prefersLargeTitles = true
            navigationBar.isTranslucent = false
            navigationItem.largeTitleDisplayMode = .automatic
        } else {
            navigationBar.largeTitleTextAttributes = [
                NSAttributedString.Key.font: UIFont.systemFont(ofSize: 26),
                NSAttributedString.Key.foregroundColor: UIColor.black
            ]
            navigationBar.titleTextAttributes = [
                NSAttributedString.Key.font: UIFont.systemFont(ofSize: 17),
                NSAttributedString.Key.foregroundColor: UIColor.black
            ]
            navigationBar.tintColor = .black
            navigationBar.prefersLargeTitles = true
            navigationBar.isTranslucent = false
            navigationItem.largeTitleDisplayMode = .automatic
            navigationBar.barTintColor = .white
        }
        
    }
    
    override var preferredStatusBarStyle: UIStatusBarStyle {
        return .darkContent
    }

    
}

here is the Tabbar Controller

class TabbarController:UITabBarController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        let c1 = C1()
        let c2 = C2()
        let c3 = C3()
        
        c1.tabBarItem = UITabBarItem(title: "Home", image: UIImage(named:  "home786"), tag: 0)
        c1.tabBarItem.tag = 0
        let nav1 = BaseNavigationController(rootViewController: c1)
        
        c2.tabBarItem = UITabBarItem(title: "Setting", image: UIImage(named:  "home786"), tag: 0)
        c2.tabBarItem.tag = 1
        let nav2 = BaseNavigationController(rootViewController: c2)
        c2.tabBarItem = UITabBarItem(title: "User", image: UIImage(named:  "home786"), tag: 0)
        c2.tabBarItem.tag = 2
        let nav3 = BaseNavigationController(rootViewController: c3)
        viewControllers = [nav1,nav2,nav3]
        selectedViewController = nav1
        tabBarController?.viewControllers?.first?.view.backgroundColor = .red
        
    }
}

Answer 2

Try to add this in viewDidLoad:

view.addSubview(UIView())

this single line block large title navigation Bar... I don't Know why, but this trick fix momentarily the issue...

Answer 3

After some research I found out what can fix my problem. If you call this method with a small delay in tabBarController didSelect then it will be possible to see a Large Title after switching viewControllers. But I still can't figure out exactly why it happened...

 DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) {
       navigationVC?.navigationBar.sizeToFit()
 }