我使用UINavigationBar扩展，使我能够隐藏/显示使用UIAppearance API的阴影或选择哪个导航栏必须隐藏/显示使用故事板(或源代码)的阴影。这是扩展:

import UIKit

private var flatAssociatedObjectKey: UInt8 = 0

/*
  An extension that adds a "flat" field to UINavigationBar. This flag, when
  enabled, removes the shadow under the navigation bar.
 */
@IBDesignable extension UINavigationBar {
    @IBInspectable var flat: Bool {
        get {
            guard let obj = objc_getAssociatedObject(self, &flatAssociatedObjectKey) as? NSNumber else {
                return false
            }
            return obj.boolValue;
        }

        set {
            if (newValue) {
                let void = UIImage()
                setBackgroundImage(void, forBarPosition: .Any, barMetrics: .Default)
                shadowImage = void
            } else {
                setBackgroundImage(nil, forBarPosition: .Any, barMetrics: .Default)
                shadowImage = nil
            }
            objc_setAssociatedObject(self, &flatAssociatedObjectKey, NSNumber(bool: newValue),
                    objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }
}

现在，要禁用所有导航条上的阴影，你必须使用:

UINavigationBar.appearance().flat = true

或者你可以使用故事板启用/禁用此行为:

从iOS 13开始，就有一个系统API来设置或删除阴影

UIKit使用shadowImage和shadowColor属性来确定阴影的 外观。当shadowImage为nil时，该工具条显示默认的着色阴影 根据shadowColor属性中的值。如果shadowColor为nil或 包含clearColor颜色，条显示没有阴影。

    let appearance = UINavigationBarAppearance()
    appearance.shadowImage = nil
    appearance.shadowColor = nil
    navigationController.navigationBar.standardAppearance = appearance

https://developer.apple.com/documentation/uikit/uibarappearance/3198009-shadowimage

在Xamarin Forms中，这对我来说很管用。只需在AppDelegate.cs上添加这个:

UINavigationBar.Appearance.ShadowImage = new UIImage();

在研究了Serhil的答案后，我创建了一个豆荚UINavigationBar+Addition，可以很容易地隐藏发际线。

#import "UINavigationBar+Addition.h"

- (void)viewDidLoad {
    [super viewDidLoad];

    UINavigationBar *navigationBar = self.navigationController.navigationBar;
    [navigationBar hideBottomHairline];
}

简单的解决方案- Swift 5

Create an extension: extension UIImage { class func hideNavBarLine(color: UIColor) -> UIImage? { let rect = CGRect(x: 0, y: 0, width: 1, height: 1) UIGraphicsBeginImageContext(rect.size) let context = UIGraphicsGetCurrentContext() context?.setFillColor(color.cgColor) context?.fill(rect) let navBarLine = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return navBarLine } } Add this to viewDidLoad(): self.navigationController?.navigationBar.shadowImage = UIImage.hideNavBarLine(color: UIColor.clear)

我使用UINavigationBar扩展，使我能够隐藏/显示使用UIAppearance API的阴影或选择哪个导航栏必须隐藏/显示使用故事板(或源代码)的阴影。这是扩展:

import UIKit

private var flatAssociatedObjectKey: UInt8 = 0

/*
  An extension that adds a "flat" field to UINavigationBar. This flag, when
  enabled, removes the shadow under the navigation bar.
 */
@IBDesignable extension UINavigationBar {
    @IBInspectable var flat: Bool {
        get {
            guard let obj = objc_getAssociatedObject(self, &flatAssociatedObjectKey) as? NSNumber else {
                return false
            }
            return obj.boolValue;
        }

        set {
            if (newValue) {
                let void = UIImage()
                setBackgroundImage(void, forBarPosition: .Any, barMetrics: .Default)
                shadowImage = void
            } else {
                setBackgroundImage(nil, forBarPosition: .Any, barMetrics: .Default)
                shadowImage = nil
            }
            objc_setAssociatedObject(self, &flatAssociatedObjectKey, NSNumber(bool: newValue),
                    objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }
}

现在，要禁用所有导航条上的阴影，你必须使用:

UINavigationBar.appearance().flat = true

或者你可以使用故事板启用/禁用此行为: