如何更改 UIBarButtonItems 的默认字体？答案

【问题标题】：How can I change the default font for UIBarButtonItems?如何更改 UIBarButtonItems 的默认字体？
【发布时间】：2019-10-23 15:02:46
【问题描述】：

我想更改所有 UIBarButtonItems 的默认字体。我的应用程序的根视图控制器中有以下代码：

    let attributes: [NSAttributedString.Key: Any] = [.font: UIFont.systemFont(ofSize: 30)]
    UIBarButtonItem.appearance().setTitleTextAttributes(attributes, for: .normal)
    UINavigationBar.appearance().titleTextAttributes = attributes
    UINavigationBarAppearance().buttonAppearance.normal.titleTextAttributes = attributes
    UIBarButtonItemAppearance().normal.titleTextAttributes = attributes
    self.navigationItem.rightBarButtonItem = UIBarButtonItem(title: "foo", style: .plain, target: nil, action: nil)

尽管外观发生了变化，但该条形按钮项的字体仍然是默认字体。如何设置默认字体？我知道我可以为每个单独的条形按钮项设置字体，但我正在寻找一种方法来广泛更改它。

【问题讨论】：

标签： ios fonts uibarbuttonitem

【解决方案1】：

iOS 13 之前

class AppDelegate : NSObject, UIApplicationDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {

        if #available(iOS 13, *) {

        }else{
            let attributes: [NSAttributedString.Key: Any] = [.font: UIFont.systemFont(ofSize: 30)]
            UIBarButtonItem.appearance().setTitleTextAttributes(attributes, for: .normal)
            UINavigationBar.appearance().titleTextAttributes = attributes
        }

        return true
    }
}

iOS 13

class MyNavigationController : UINavigationController {

    override init(rootViewController: UIViewController) {
        super.init(rootViewController: rootViewController)
        if #available(iOS 13, *) {
            let attributes: [NSAttributedString.Key: Any] = [.font: UIFont.systemFont(ofSize: 30)]
            let appearance = UINavigationBarAppearance()
            appearance.buttonAppearance.normal.titleTextAttributes = attributes
            appearance.titleTextAttributes = attributes
            self.navigationBar.standardAppearance = appearance
        }
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

【讨论】：

【解决方案2】：

您可以使用 UINavigationBarAppearance 自定义所有导航栏，但您需要在导航栏的外观代理上设置 standardAppearance - 调用如下：

UINavigationBarAppearance().buttonAppearance.normal.titleTextAttributes = attributes
UIBarButtonItemAppearance().normal.titleTextAttributes = attributes

孤立地什么也不做，因为他们创造了一个新的外观，设置一个值，然后把它扔掉。而是这样做：

let appearance = UINavigationBarAppearance()
appearance.buttonAppearance.normal.titleTextAttributes = attributes
UINavigationBar.appearance().standardAppearance = appearance

【讨论】：