基于MVVM+C模式修改UINavigationBar返回按钮的问题求助

• 错误赋值backBarButtonItem：该属性作用于当前控制器push出的下一级页面的返回按钮，给导航控制器本身的navigationItem设置完全无效，需要在全局外观中统一配置
• iOS13+ 外观优先级问题：使用UINavigationBarAppearance配置导航栏样式后，单独修改UINavigationBar的backIndicatorImage等属性会被更高优先级的appearance配置覆盖，必须把返回按钮相关配置也写入appearance
• 导航栏显隐切换导致样式重置：在viewWillAppear/viewWillDisappear中切换导航栏显隐时，部分系统版本会重置导航栏样式，需要确保样式配置为全局生效

将AppDelegate中导航栏初始化代码替换为以下内容即可：

let navigationController: UINavigationController = .init()
// 如果需要保留自定义图片的原色，将.alwaysTemplate改为.alwaysOriginal
let backButtonImage = UIImage(named: "backButton")?.withRenderingMode(.alwaysTemplate)

if #available(iOS 13.0, *) {
    let appearance = UINavigationBarAppearance()
    appearance.configureWithOpaqueBackground()
    appearance.backgroundColor = .backgroundColor
    appearance.shadowColor = nil
    appearance.shadowImage = nil
    
    // 配置返回按钮自定义图片
    appearance.setBackIndicatorImage(backButtonImage, transitionMaskImage: backButtonImage)
    // 隐藏返回按钮文字：将文字偏移到屏幕可视范围外
    appearance.backButtonAppearance.normal.titlePositionAdjustment = UIOffset(horizontal: -1000, vertical: 0)
    
    navigationController.navigationBar.standardAppearance = appearance
    navigationController.navigationBar.scrollEdgeAppearance = appearance
    // 适配横竖屏切换场景
    navigationController.navigationBar.compactAppearance = appearance
} else {
    navigationController.navigationBar.isTranslucent = false
    navigationController.navigationBar.barTintColor = .backgroundColor
    navigationController.navigationBar.shadowImage = nil
    navigationController.navigationBar.shadowColor = nil
    
    // iOS13以下版本配置返回按钮
    navigationController.navigationBar.backIndicatorImage = backButtonImage
    navigationController.navigationBar.backIndicatorTransitionMaskImage = backButtonImage
    // 全局隐藏返回按钮文字
    UIBarButtonItem.appearance().setBackButtonTitlePositionAdjustment(UIOffset(horizontal: -1000, vertical: 0), for: .default)
}

navigationController.navigationBar.tintColor = .primary

window?.rootViewController = navigationController
window?.makeKeyAndVisible()

如果修改后出现侧滑返回功能失效的问题，添加以下扩展即可恢复：

extension UINavigationController: UIGestureRecognizerDelegate {
    override open func viewDidLoad() {
        super.viewDidLoad()
        interactivePopGestureRecognizer?.delegate = self
    }

    public func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        return viewControllers.count > 1
    }
}

内容的提问来源于stack exchange，提问作者Peter Hlavatík