Ios 设置导航栏背景图像

这是我的代码：

let logo = UIImage(named: "navigationbar")
self.navigationController!.navigationBar.setBackgroundImage(logo!.resizableImage(withCapInsets: UIEdgeInsets(top: 0,left: 0, bottom: 0 ,right: 0), resizingMode: .stretch), for: .default)

但它不起作用。这是错误代码

线程1:致命错误：在展开文件时意外发现nil 可选值

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请尝试此代码以查看代码崩溃的位置。。。。它的出发点。。然后解出零的那部分。。。在您的代码中，

navigationController

或

Image

为零

if let logo = UIImage(named: "navigationbar") {
    if let navigation = self.navigationController {

       navigation.navigationBar.setBackgroundImage(logo!.resizableImage(withCapInsets: UIEdgeInsets(top: 0,left: 0, bottom: 0 ,right: 0), resizingMode: .stretch), for: .default)
      }else {
        print("Navigation cotroller not found and its nil")
      }
} else {
   print("problem wiyh image file")
}

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您的控制器绝对不是导航控制器，如果它是您在应用程序中显示的第一个控制器，则必须在WillConnector下的场景代理中将其设置为如下功能：

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
    // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
    // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
    guard let windowScene = (scene as? UIWindowScene) else { return }
    window = UIWindow(windowScene: windowScene)
    window?.makeKeyAndVisible()
    let controller = UINavigationController(rootViewController: ViewController())
    window?.rootViewController = controller
}

@objc fileprivate func callNavigationController() {
let controller = UINavigationController(rootViewController: YourController())
controller.modalPresentationStyle = .fullScreen
present(controller, animated: true, completion: nil)
}

如果您使用按钮操作集函数调用控制器，该函数显示如下导航控制器：

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
    // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
    // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
    guard let windowScene = (scene as? UIWindowScene) else { return }
    window = UIWindow(windowScene: windowScene)
    window?.makeKeyAndVisible()
    let controller = UINavigationController(rootViewController: ViewController())
    window?.rootViewController = controller
}

@objc fileprivate func callNavigationController() {
let controller = UINavigationController(rootViewController: YourController())
controller.modalPresentationStyle = .fullScreen
present(controller, animated: true, completion: nil)
}

现在在viewDidLoad中设置导航栏背景， 第一个使用guard let语句展开图像：

guard let logo = UIImage(named: "navigationbar") else { return }

设置导航栏背景图像后：

navigationController?.navigationBar.setBackgroundImage(logo.resizableImage(withCapInsets: UIEdgeInsets(top: 0,left: 0, bottom: 0 ,right: 0), resizingMode: .stretch), for: .default)

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就这些

哦，太酷了。打印“未找到导航滚轮及其零”。我是初学者：（（现在你需要检查为什么为零，因为你需要发布代码…你在哪里添加它？我在viewDidLoad（）函数中添加了你的代码。但我不知道如何检查为什么为零。我应该导入Navigationbar吗？你的控制器在navigation controller中？