如何在TabBarController下仅隐藏两个ViewController的NavigationBar

问题根源：当两个需要隐藏导航栏的ViewController（timerView和rankingView）之间切换时，前一个VC的viewWillDisappear会先将导航栏设为显示，而后一个VC的viewWillAppear才会将其隐藏，中间的状态切换导致导航栏短暂显示。

以下两种方案可解决该问题：

方案一：修改单个VC的消失逻辑 #

在TimerViewController和RankingViewController中，仅当即将切换到需要显示导航栏的TeamViewController时，才恢复导航栏显示：

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    
    // 判断即将显示的VC是否为需要显示导航栏的类型
    guard let tabBarVC = tabBarController,
          let nextVC = tabBarVC.selectedViewController else {
        return
    }
    
    // 只有切换到TeamViewController时才恢复导航栏
    if nextVC is TeamViewController {
        navigationController?.setNavigationBarHidden(false, animated: animated)
    }
}

保留原有的viewWillAppear代码不变：

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    navigationController?.setNavigationBarHidden(true, animated: animated)
}

方案二：在TabBarController中统一控制导航栏状态（推荐） #

将导航栏的显示逻辑集中到PlayerTabBarController中，避免多个VC各自处理导致的冲突：

1. 修改PlayerTabBarController代码，让其遵守UITabBarControllerDelegate并统一管理导航栏状态：

class PlayerTabBarController: UITabBarController, UITabBarControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        configureNavBar()
        self.delegate = self // 设置代理
    }
    
    func configureNavBar() {
        let backButton = UIButton(frame: CGRect(x: 0, y: 0, width: 20, height: 10))
        backButton.setImage(UIImage(named: "leave 1"), for: .normal)
        backButton.addTarget(self, action: #selector(onBackPressed), for: .touchUpInside)
        let barBackButton = UIBarButtonItem(customView: backButton)
        self.navigationItem.leftBarButtonItem = barBackButton
    }

    @objc func onBackPressed() {
        self.navigationController?.popViewController(animated: true)
    }
    
    // Tab切换时更新导航栏状态
    func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
        let shouldHide = viewController is TimerViewController || viewController is RankingViewController
        navigationController?.setNavigationBarHidden(shouldHide, animated: true)
    }
    
    // 初始加载时设置正确的导航栏状态
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        guard let selectedVC = selectedViewController else { return }
        let shouldHide = selectedVC is TimerViewController || selectedVC is RankingViewController
        navigationController?.setNavigationBarHidden(shouldHide, animated: false)
    }
}

2. 删除TimerViewController和RankingViewController中所有关于setNavigationBarHidden的代码，避免重复处理。

内容的提问来源于stack exchange，提问作者nakim81