iOS Swift中代码结合IBOutlet创建UITabBar不显示视图控制器的解决方法

你的代码存在几个核心问题，导致TabBar无法正常加载并显示ViewController：

1. 复制粘贴错误 #

创建secondVC时，错误地对firstVC重复赋值，所有属性操作都应指向secondVC本身：

// 原错误代码
let secondVC = SecondViewController()
firstVC.name = nameVal // 应为 secondVC.name = nameVal
firstVC.tabBarItem = ... // 应为 secondVC.tabBarItem = ...

2. TabBar条目赋值类型错误 #

UITabBar.items需要的是UITabBarItem类型数组，你直接传入了UIViewController数组，TabBar无法识别正确的条目。正确做法是提取每个VC的tabBarItem：

// 原错误代码
tabBarCnt.items = [firstVC, secondVC, thirdVC]
// 修正后
tabBarCnt.items = [firstVC.tabBarItem, secondVC.tabBarItem, thirdVC.tabBarItem]

3. 未管理ViewController的显示逻辑 #

你仅创建了VC实例，但没有将它们添加为当前控制器的子控制器，也未实现TabBar切换时的VC显示/隐藏逻辑。

方案一：改用系统UITabBarController（推荐） #

系统UITabBarController会自动处理VC的管理和切换，实现更简洁：

public class TabBarViewController: UITabBarController {

    override public func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
        setupTabBarItems()
    }

    func setupTabBarItems() {
        // 第一个页面
        let firstVC = FirstViewController()
        firstVC.name = nameVal
        let firstTab = UITabBarItem(title: nil, image: UIImage(named: "ico_active", in: Bundle(for: Self.self), compatibleWith: nil), tag: 0)
        firstTab.imageInsets = UIEdgeInsets(top: 5, left: 0, bottom: -5, right: 0)
        firstVC.tabBarItem = firstTab

        // 第二个页面
        let secondVC = SecondViewController()
        secondVC.name = nameVal
        let secondTab = UITabBarItem(title: nil, image: UIImage(named: "ico_active", in: Bundle(for: Self.self), compatibleWith: nil), tag: 1)
        secondTab.imageInsets = UIEdgeInsets(top: 5, left: 0, bottom: -5, right: 0)
        secondVC.tabBarItem = secondTab

        // 第三个页面
        let thirdVC = ThirdViewController()
        thirdVC.name = nameVal
        let thirdTab = UITabBarItem(title: nil, image: UIImage(named: "ico_active", in: Bundle(for: Self.self), compatibleWith: nil), tag: 2)
        thirdTab.imageInsets = UIEdgeInsets(top: 5, left: 0, bottom: -5, right: 0)
        thirdVC.tabBarItem = thirdTab

        // 将页面添加到TabBarController
        self.viewControllers = [firstVC, secondVC, thirdVC]
    }
}

// 可选：实现切换事件监听
extension TabBarViewController: UITabBarControllerDelegate {
    func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
        // 处理页面切换后的逻辑
    }
}

方案二：修复自定义UIViewController+UITabBar的实现 #

如果坚持手动管理TabBar，需要添加子控制器并实现切换逻辑：

public class TabBarViewController: UIViewController, UITabBarDelegate {

    @IBOutlet weak var tabBarCnt: UITabBar!
    private var childVCs: [UIViewController] = []
    private var currentShowVC: UIViewController?

    override public func viewDidLoad() {
        super.viewDidLoad()
        tabBarCnt.delegate = self
        setupTabBarAndVCs()
        // 默认显示第一个页面
        if let firstVC = childVCs.first {
            switchToVC(firstVC)
        }
    }

    func setupTabBarAndVCs() {
        // 初始化三个页面
        let firstVC = FirstViewController()
        firstVC.name = nameVal
        firstVC.tabBarItem = createTabItem(tag: 0)

        let secondVC = SecondViewController()
        secondVC.name = nameVal
        secondVC.tabBarItem = createTabItem(tag: 1)

        let thirdVC = ThirdViewController()
        thirdVC.name = nameVal
        thirdVC.tabBarItem = createTabItem(tag: 2)

        childVCs = [firstVC, secondVC, thirdVC]
        tabBarCnt.items = childVCs.map { $0.tabBarItem! }
    }

    // 封装TabBarItem创建逻辑
    private func createTabItem(tag: Int) -> UITabBarItem {
        let tabItem = UITabBarItem(title: nil, image: UIImage(named: "ico_active", in: Bundle(for: Self.self), compatibleWith: nil), tag: tag)
        tabItem.imageInsets = UIEdgeInsets(top: 5, left: 0, bottom: -5, right: 0)
        return tabItem
    }

    // 切换页面逻辑
    private func switchToVC(_ targetVC: UIViewController) {
        // 移除当前页面
        currentShowVC?.view.removeFromSuperview()
        currentShowVC?.removeFromParent()

        // 添加目标页面
        addChild(targetVC)
        targetVC.view.frame = CGRect(x: 0, y: 0, width: view.bounds.width, height: view.bounds.height - tabBarCnt.bounds.height)
        view.insertSubview(targetVC.view, belowSubview: tabBarCnt)
        targetVC.didMove(toParent: self)

        currentShowVC = targetVC
    }

    // TabBar切换回调
    func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem) {
        guard let targetVC = childVCs.first(where: { $0.tabBarItem?.tag == item.tag }) else { return }
        switchToVC(targetVC)
    }
}

内容的提问来源于stack exchange，提问作者PvUIDev