不同的UINavigationControllers中出现不同的外观

Question

在iOS 11中,我正在更改导航控制器的后退按钮,如下所示:

UINavigationBar.appearance().backIndicatorImage = whiteBackButtonImage!.withRenderingMode(.alwaysOriginal)
UINavigationBar.appearance().backIndicatorTransitionMaskImage = whiteBackButtonImage!.withRenderingMode(.alwaysOriginal)

这似乎工作正常,问题是当我想区分两种使用不同背面图像的UINavigationControllers:

let whiteNavigationBarAppearance = UINavigationBar.appearance(whenContainedInInstancesOf: [WhiteNavigationController.self])
whiteNavigationBarAppearance.backIndicatorImage = greenBackButtonImage!.withRenderingMode(.alwaysOriginal)
whiteNavigationBarAppearance.backIndicatorTransitionMaskImage = greenBackButtonImage!.withRenderingMode(.alwaysOriginal)

let greenNavigationBarAppearance = UINavigationBar.appearance(whenContainedInInstancesOf: [GreenNavigationController.self])
greenNavigationBarAppearance.backIndicatorImage = whiteBackButtonImage!.withRenderingMode(.alwaysOriginal)
greenNavigationBarAppearance.backIndicatorTransitionMaskImage = whiteBackButtonImage!.withRenderingMode(.alwaysOriginal)

使用第二种方法,会显示常规后退按钮,因此无论如何它都无法识别更改.有谁知道我的方法有什么问题？

Answer 1

我在业余项目中重新创建了您的场景，并且您提供的代码片段工作得很好。我认为您的视图控制器层次结构中可能有一些东西。

这就是我构建层次结构的方式。ViewController有一个按钮可以推动UIViewController导航堆栈上的另一个按钮。

let redViewController = ViewController()
redViewController.view.backgroundColor = .red

let greenViewController = ViewController()
greenViewController.view.backgroundColor = .green

let red = RedNavigationController(rootViewController: redViewController)
red.tabBarItem = UITabBarItem(tabBarSystemItem: .bookmarks, tag: 1)

let green = GreenNavigationController(rootViewController: greenViewController)
green.tabBarItem = UITabBarItem(tabBarSystemItem: .contacts, tag: 2)

let tabBarController = UITabBarController()
tabBarController.setViewControllers([red, green], animated: false)
tabBarController.selectedIndex = 0

这就是我设置外观的方式。

let image1 = UIImage(named: "Button")!.withRenderingMode(.alwaysOriginal)
let image2 = UIImage(named: "Button2")!.withRenderingMode(.alwaysOriginal)

let red = UINavigationBar.appearance(whenContainedInInstancesOf: [RedNavigationController.self])
red.backIndicatorImage = image1
red.backIndicatorTransitionMaskImage = image1

let green = UINavigationBar.appearance(whenContainedInInstancesOf: [GreenNavigationController.self])
green.backIndicatorImage = image2
green.backIndicatorTransitionMaskImage = image2

这就是结果