如何实现UITabBarController中仅启动可见的隐藏欢迎页面？

Hey there! Let's figure out how to add that one-time welcome page to your UITabBarController setup. I'll cover both Storyboard and code-based solutions since you asked about both—plus explain why your earlier attempt might not have worked.

Here's how to set this up using Storyboard:

1. Design your welcome page

   • Add a new UIViewController to your Storyboard, customize its layout (add a welcome message, "Enter App" button, etc.), and give it a Storyboard ID like WelcomeViewController.
   • Make sure your existing UITabBarController has a Storyboard ID too (e.g., MainTabBarController).

2. Control root controller on app launch

   • Open your SceneDelegate.swift (or AppDelegate.swift if you're using an older project structure).
   • In the scene(_:willConnectTo:options:) method, check if the user has already seen the welcome page using UserDefaults:

     func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
         guard let windowScene = (scene as? UIWindowScene) else { return }
         let window = UIWindow(windowScene: windowScene)
         self.window = window
         
         // Check if welcome page was already shown
         let hasShownWelcome = UserDefaults.standard.bool(forKey: "hasShownWelcomePage")
         
         if hasShownWelcome {
             // Show TabBarController directly
             let tabBarVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "MainTabBarController") as! UITabBarController
             window.rootViewController = tabBarVC
         } else {
             // Show welcome page first
             let welcomeVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "WelcomeViewController") as! WelcomeViewController
             window.rootViewController = welcomeVC
         }
         
         window.makeKeyAndVisible()
     }
     

3. Add transition logic to welcome page

   • Connect your "Enter App" button to an action in the welcome view controller:

     @IBAction func enterAppButtonTapped(_ sender: UIButton) {
         // Mark welcome page as shown
         UserDefaults.standard.set(true, forKey: "hasShownWelcomePage")
         
         // Load TabBarController and set it as root
         guard let tabBarVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "MainTabBarController") as? UITabBarController else { return }
         
         // Replace root controller (no way to go back to welcome page)
         UIApplication.shared.keyWindow?.rootViewController = tabBarVC
     }
     

If you prefer a code-only approach, here's how to do it:

1. Create your welcome view controller

   class WelcomeViewController: UIViewController {
       override func viewDidLoad() {
           super.viewDidLoad()
           view.backgroundColor = .white
           
           // Add "Enter App" button
           let enterButton = UIButton(type: .system)
           enterButton.setTitle("Enter App", for: .normal)
           enterButton.addTarget(self, action: #selector(enterAppTapped), for: .touchUpInside)
           enterButton.translatesAutoresizingMaskIntoConstraints = false
           view.addSubview(enterButton)
           
           NSLayoutConstraint.activate([
               enterButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),
               enterButton.centerYAnchor.constraint(equalTo: view.centerYAnchor)
           ])
       }
       
       @objc private func enterAppTapped() {
           UserDefaults.standard.set(true, forKey: "hasShownWelcomePage")
           let tabBarVC = createTabBarController()
           UIApplication.shared.keyWindow?.rootViewController = tabBarVC
       }
   }
   

2. Create your TabBarController programmatically

   func createTabBarController() -> UITabBarController {
       let tabBarVC = UITabBarController()
       
       // Create your 5 tab view controllers
       let tab1VC = UIViewController()
       tab1VC.tabBarItem = UITabBarItem(title: "Tab 1", image: UIImage(systemName: "house"), tag: 0)
       tab1VC.view.backgroundColor = .red
       
       let tab2VC = UIViewController()
       tab2VC.tabBarItem = UITabBarItem(title: "Tab 2", image: UIImage(systemName: "person"), tag: 1)
       tab2VC.view.backgroundColor = .blue
       
       // Repeat for tabs 3,4,5...
       
       tabBarVC.viewControllers = [tab1VC, tab2VC, tab3VC, tab4VC, tab5VC]
       return tabBarVC
   }
   

3. Set root controller on launch
   In SceneDelegate.swift:

   func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
       guard let windowScene = (scene as? UIWindowScene) else { return }
       let window = UIWindow(windowScene: windowScene)
       self.window = window
       
       let hasShownWelcome = UserDefaults.standard.bool(forKey: "hasShownWelcomePage")
       
       if hasShownWelcome {
           window.rootViewController = createTabBarController()
       } else {
           window.rootViewController = WelcomeViewController()
       }
       
       window.makeKeyAndVisible()
   }
   

When you set the welcome view controller as the root directly but didn't properly switch to the UITabBarController afterwards, the tab bar never got loaded as the root. Using root controller replacement (instead of presenting or pushing) ensures the welcome page is completely removed from the view hierarchy—so users can't navigate back to it by switching tabs or using the back button.

内容的提问来源于stack exchange，提问作者Shinox