在swift 4下更改导航控制器后退按钮上的字体

Question

Swift 4，iOS 11.2.5 Xcode 9.2

尝试更改后退按钮的字体。找到了以前尝试过的解决方案，但是在我的配置（选项卡栏控制器内的导航控制器）下，似乎在Swift 4，iOS 11.2.5下都无法正常工作。

得到此代码后，第一行和最后一行有效，但中间的三行无效。

self.navigationController?.navigationBar.titleTextAttributes = [ NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!]
navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .normal)
navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .highlighted)
navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .focused)
navigationItem.title = "Filter \(titleSelection!) [shake to clear]"

这是viewDidLoad方法。应该行吗？

Answer 1

对于Swift 4，U可以在AppDelegate中尝试此操作。

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        UIBarButtonItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.red, NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 15)!], for: UIControlState.normal)

        UIBarButtonItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.green, NSAttributedStringKey.font : UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)! ], for: .highlighted)
        UIBarButtonItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.blue, NSAttributedStringKey.font : UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)! ], for: .focused)

        return true
}

在ViewController中。

override func viewWillAppear(_ animated: Bool) {

    self.title = "List"
    self.navigationController?.navigationBar.titleTextAttributes = [ NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!]

    // THE BELOW THREE LINES NOT WORKING.

    //navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .normal)

    //navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .highlighted)

    //navigationItem.backBarButtonItem?.setTitleTextAttributes([NSAttributedStringKey.font: UIFont(name: "AvenirNextCondensed-DemiBoldItalic", size: 20)!], for: .focused)

}

故事板

输出量