如何通过代码为Navigation Controller的所有ViewController添加右侧Bar Button Item

问题描述 #

在Scene Delegate中创建UINavigationController后，尝试直接给导航控制器设置右侧Bar Button Item，但没有任何ViewController显示该按钮：

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
   
    guard let windowScene = (scene as? UIWindowScene) else { return }
 
    let window = UIWindow(windowScene: windowScene)

    let viewController = IntroViewController()
    let navigation = UINavigationController(rootViewController: viewController)
    
    // 这段代码无效，导航栏显示的是栈顶VC的navigationItem
    navigation.navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Test", style: .done, target: nil, action: nil)
    navigation.navigationItem.rightBarButtonItem?.tintColor = .red
    
    let standardAppearance = UINavigationBarAppearance()
    standardAppearance.backgroundColor = .black
    
    navigation.navigationBar.standardAppearance = standardAppearance
    navigation.navigationBar.scrollEdgeAppearance = standardAppearance
    

    window.rootViewController = navigation
    self.window = window
    window.makeKeyAndVisible()
}

只有在单个ViewController的viewDidLoad中设置，该VC才会显示按钮：

self.navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Exit", style: .plain, target: self, action: #selector(exitPressed))

原因分析 #

UINavigationController自身的navigationItem不会被导航栏显示，导航栏始终展示当前导航栈顶部ViewController的navigationItem，所以直接给导航控制器设置按钮是无效的。

解决方案 #

方案一：创建UIViewController基类（推荐） #

定义一个基类，所有需要显示右侧按钮的ViewController都继承这个基类：

class BaseViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // 统一添加右侧按钮
        let rightButton = UIBarButtonItem(title: "Test", style: .done, target: self, action: #selector(rightButtonTapped))
        rightButton.tintColor = .red
        navigationItem.rightBarButtonItem = rightButton
    }
    
    @objc func rightButtonTapped() {
        // 通用点击逻辑，子类可重写
        print("右侧按钮被点击")
    }
}

修改业务ViewController的继承关系：

class IntroViewController: BaseViewController {
    // 若需自定义按钮，可重写viewDidLoad或rightButtonTapped方法
}

优点：逻辑清晰、易维护，子类可灵活扩展，是最安全的方案。

方案二：利用UINavigationController代理 #

通过导航控制器的代理方法，在ViewController即将显示时统一设置按钮：

1. 让SceneDelegate遵守UINavigationControllerDelegate
2. 在SceneDelegate中添加代码：

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    guard let windowScene = (scene as? UIWindowScene) else { return }
 
    let window = UIWindow(windowScene: windowScene)

    let viewController = IntroViewController()
    let navigation = UINavigationController(rootViewController: viewController)
    // 设置代理
    navigation.delegate = self
    
    let standardAppearance = UINavigationBarAppearance()
    standardAppearance.backgroundColor = .black
    
    navigation.navigationBar.standardAppearance = standardAppearance
    navigation.navigationBar.scrollEdgeAppearance = standardAppearance
    
    window.rootViewController = navigation
    self.window = window
    window.makeKeyAndVisible()
}

// MARK: - UINavigationControllerDelegate
func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
    // 避免重复设置按钮
    guard viewController.navigationItem.rightBarButtonItem == nil else { return }
    
    let rightButton = UIBarButtonItem(title: "Test", style: .done, target: viewController, action: #selector(viewController.rightButtonTapped))
    rightButton.tintColor = .red
    viewController.navigationItem.rightBarButtonItem = rightButton
}

3. 给UIViewController添加扩展实现点击方法：

extension UIViewController {
    @objc func rightButtonTapped() {
        print("右侧按钮被点击")
        // 子类可重写此方法实现自定义逻辑
    }
}

优点：无需修改现有ViewController的继承关系，适合已有项目。

方案三：方法Swizzling（谨慎使用） #

通过运行时替换viewDidLoad方法，自动给所有ViewController添加按钮：

extension UIViewController {
    static func swizzleViewDidLoad() {
        let originalSelector = #selector(viewDidLoad)
        let swizzledSelector = #selector(swizzledViewDidLoad)
        
        guard let originalMethod = class_getInstanceMethod(self, originalSelector),
              let swizzledMethod = class_getInstanceMethod(self, swizzledSelector) else { return }
        
        method_exchangeImplementations(originalMethod, swizzledMethod)
    }
    
    @objc func swizzledViewDidLoad() {
        // 先执行原viewDidLoad逻辑
        self.swizzledViewDidLoad()
        
        // 排除UINavigationController本身，避免重复设置
        guard self is UINavigationController == false else { return }
        
        if navigationItem.rightBarButtonItem == nil {
            let rightButton = UIBarButtonItem(title: "Test", style: .done, target: self, action: #selector(rightButtonTapped))
            rightButton.tintColor = .red
            navigationItem.rightBarButtonItem = rightButton
        }
    }
    
    @objc func rightButtonTapped() {
        print("右侧按钮被点击")
    }
}

在SceneDelegate的scene方法开头调用Swizzle：

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    // 执行Swizzle
    UIViewController.swizzleViewDidLoad()
    
    // 后续原有代码...
}

注意：Swizzling属于运行时黑魔法，可能与第三方库冲突，调试难度大，仅在必要时使用。

内容的提问来源于stack exchange，提问作者Shiv Nik