对于Swift 3.0:

override func viewDidLoad() {
    super.viewDidLoad()

    navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)
    navigationController?.navigationBar.shadowImage = UIImage()
    navigationController?.navigationBar.isTranslucent = true
}

下面的代码扩展了为这个线程选择的顶部答案，以消除底部边框并设置文本颜色:

The last two coded lines of this code set transparency. I borrowed that code from this thread and it worked perfectly! The "clipsToBounds" property was code I found which got rid of the bottom border line with OR without transparency set (so if you decide to go with a solid white/black/etc. background instead, there will still be no border line). The "tintColor" line (2nd coded line) set my back button to a light grey I kept barTintColor as a backup. I don't know why transparency would not work, but if it doesn't, I want my bg white as I used to have it let navigationBarAppearace = UINavigationBar.appearance() navigationBarAppearace.tintColor = UIColor.lightGray navigationBarAppearace.barTintColor = UIColor.white navigationBarAppearace.clipsToBounds = true navigationBarAppearace.isTranslucent = true navigationBarAppearace.setBackgroundImage(UIImage(), for: .default) navigationBarAppearace.shadowImage = UIImage()

IOS7:

self.navigationController.navigationBar.translucent = YES;
self.navigationController.navigationBar.shadowImage = [UIImage new];
self.navigationController.view.backgroundColor = [UIColor clearColor];
[self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
self.navigationController.navigationBar.backgroundColor = [UIColor clearColor];

你的意思是完全透明，还是使用照片应用程序中看到的半透明黑色?后者你可以通过设置它的barStyle属性为uibarstyleblack半透明来实现。前……我不太确定。如果您希望其中的项仍然可见，您可能必须在栏的视图层次结构中进行一些挖掘，并删除包含其背景的视图。

解决方案- Swift 5 - iOS 13+

根据文档，在你的UIViewController子类中:

override func viewDidLoad()
{
    super.viewDidLoad()
    
    let appearance = UINavigationBarAppearance()
    appearance.configureWithTransparentBackground()
    //appearance.backgroundColor = UIColor.clear
    
    navigationItem.compactAppearance = appearance
    navigationItem.scrollEdgeAppearance = appearance
    navigationItem.standardAppearance = appearance
    
    //...
}

只是为了澄清，这使得UINavigationBar完全透明。栏按钮项仍然可见，并正常工作。

什么不起作用

override func viewDidLoad()
{
    super.viewDidLoad()
    
    navigationController?.navigationBar.isTranslucent = true
    navigationController?.navigationBar.isOpaque = false

    //...
}

这让我意识到我其实不知道透明RIP和半透明RIP之间的区别。

参考文献

https://developer.apple.com/documentation/uikit/uinavigationcontroller/customizing_your_app_s_navigation_bar

https://www.lexico.com/en/definition/transparent

https://www.lexico.com/en/definition/translucent

更新08/10/2021

在以我提供的方式设置外观后，更改navigationItem栏按钮将重置外观，您必须再次执行此操作。

c# / Xamarin解决方案

NavigationController.NavigationBar.SetBackgroundImage(new UIImage(), UIBarMetrics.Default);
NavigationController.NavigationBar.ShadowImage = new UIImage();
NavigationController.NavigationBar.Translucent = true;