问题描述

我无法更改导航栏上的提示颜色.我在 viewDidLoad 中尝试了下面的代码，但没有任何反应.

I am unable to change the prompt color on my navigation bar. I've tried the code below in viewDidLoad, but nothing happens.

self.navigationController?.navigationBar.titleTextAttributes = [NSAttributedStringKey.foregroundColor: UIColor.white]

我错过了什么吗?上面的代码错了吗?

Am I missing something? Is the code above wrong?

推荐答案

看来你是对的.您需要使用 UIAppearance 在 iOS 11 上设置提示文本样式.

It seems like you're right about this one. You need to use UIAppearance to style the prompt text on iOS 11.

我已经提交了雷达 #34758558，即 titleTextAttributes 属性刚刚停止在 iOS 11 中提示提示.

I've filed radar #34758558 that the titleTextAttributes property just stopped working for prompt in iOS 11.

好消息是有几个变通方法，我们可以通过使用 Xcode 的视图层次调试器来发现:

The good news is that there are a couple of workarounds, which we can uncover by using Xcode's view hierarchy debugger:

// 1. This works, but potentially changes *all* labels in the navigation bar. 
// If you want this, it works.
UILabel.appearance(whenContainedInInstancesOf: [UINavigationBar.self]).textColor = UIColor.white

提示只是一个UILabel.如果我们使用 UIAppearance 的 whenContainedInInstancesOf:，我们可以很容易地按照我们想要的方式更新颜色.

The prompt is just a UILabel. If we use UIAppearance's whenContainedInInstancesOf:, we can pretty easily update the color the way we want.

如果您仔细观察，您会注意到 UILabel 上还有一个包装器视图.它有自己的类，可能会响应 UIAppearance...

If you look closely, you'll notice that there's also a wrapper view on the UILabel. It has its own class that might respond to UIAppearance...

// 2. This is a more precise workaround but it requires using a private class.

if let promptClass = NSClassFromString("_UINavigationBarModernPromptView") as? UIAppearanceContainer.Type
{
  UILabel.appearance(whenContainedInInstancesOf: [promptClass]).textColor = UIColor.white
}

我建议坚持使用更通用的解决方案，因为它不使用私有 API.(应用审查等)看看这两种解决方案中的任何一种都有什么效果:

I'd advise sticking to the more general solution, since it doesn't use private API. (App review, etc.) Check out what you get with either of these two solutions:

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