我也遇到了同样的问题，但没有一个答案真正令人满意。以下是我对Swift3的看法:

func hideNavigationBarLine() {
    navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)
    navigationController?.navigationBar.shadowImage = UIImage()
}

只需在viewDidLoad()中调用它。

pxpgraphics的解决方案为Swift 2.0更新

extension UINavigationBar {

    func hideBottomHairline()
    {
        hairlineImageViewInNavigationBar(self)?.hidden = true
    }

    func showBottomHairline()
    {
        hairlineImageViewInNavigationBar(self)?.hidden = false
    }

    private func hairlineImageViewInNavigationBar(view: UIView) -> UIImageView?
    {
        if let imageView = view as? UIImageView where imageView.bounds.height <= 1
        {
            return imageView
        }

        for subview: UIView in view.subviews
        {
            if let imageView = hairlineImageViewInNavigationBar(subview)
            {
                return imageView
            }
        }

        return nil
    }

}

extension UIToolbar
{

    func hideHairline()
    {
        let navigationBarImageView = hairlineImageViewInToolbar(self)?.hidden = true
    }

    func showHairline()
    {
        let navigationBarImageView = hairlineImageViewInToolbar(self)?.hidden = false
    }

    private func hairlineImageViewInToolbar(view: UIView) -> UIImageView?
    {
        if let imageView = view as? UIImageView where imageView.bounds.height <= 1
        {
            return imageView
        }

        for subview: UIView in view.subviews
        {
            if let imageView = hairlineImageViewInToolbar(subview)
            {
                return imageView
            }
        }

        return nil
    }

}

        if #available(iOS 13.0, *) {
            let appearance = UINavigationBarAppearance()
            appearance.backgroundColor          = Colors.color_app
            appearance.titleTextAttributes      = [.foregroundColor : UIColor.white]
            appearance.largeTitleTextAttributes = [.foregroundColor : UIColor.white]
            appearance.shadowColor = .clear
            appearance.shadowImage = UIImage()
            
            UINavigationBar.appearance().tintColor            = .white
            UINavigationBar.appearance().standardAppearance   = appearance
            UINavigationBar.appearance().compactAppearance    = appearance
            UINavigationBar.appearance().scrollEdgeAppearance = appearance
        } else {
            UINavigationBar.appearance().barTintColor        = Colors.color_app
            UINavigationBar.appearance().tintColor           = .white
            UINavigationBar.appearance().titleTextAttributes = [NSAttributedString.Key.foregroundColor : UIColor.white]
            if #available(iOS 11.0, *) {
                UINavigationBar.appearance().largeTitleTextAttributes = [NSAttributedString.Key.foregroundColor: UIColor.white]
            }
            UINavigationBar.appearance().isTranslucent = false
            
            UINavigationBar.appearance().shadowImage = UIImage()
            UINavigationBar.appearance().setBackgroundImage(UIImage(), for: .default)
        }

两条线的解决方案对我来说很有效。尝试在ViewDidLoad方法中添加这个:

navigationController?.navigationBar.setValue(true, forKey: "hidesShadow")
self.extendedLayoutIncludesOpaqueBars = true

我刚刚为这个创建了一个扩展…关于格式的问题很抱歉(这是我的第一个答案)。

用法:

  override func viewDidLoad() {
    super.viewDidLoad()
    self.navigationController?.hideShadow = true
}

扩展:

 UINavigationController.swift
//  Created by Ricardo López Rey on 16/7/15.

import Foundation


struct UINavigationControllerExtension {
    static var hideShadowKey : String = "HideShadow"
static let backColor = UIColor(red: 247/255, green: 247/255, blue: 248/255, alpha: 1.0)
}

extension UINavigationController {

    var hideShadow : Bool {
        get {
            if let ret =  objc_getAssociatedObject(self, &UINavigationControllerExtension.hideShadowKey) as? Bool {
                return ret
            } else {
                return false
            }


        }
        set {
            objc_setAssociatedObject(self,&UINavigationControllerExtension.hideShadowKey,newValue, objc_AssociationPolicy(OBJC_ASSOCIATION_RETAIN_NONATOMIC))

            if newValue {


            self.navigationBar.setBackgroundImage(solidImage(UINavigationControllerExtension.backColor), forBarMetrics: UIBarMetrics.Default)

                self.navigationBar.shadowImage = solidImage(UIColor.clearColor())
            } else {
                self.navigationBar.setBackgroundImage(nil, forBarMetrics: UIBarMetrics.Default)
            }
        }
    }

    private func solidImage(color: UIColor, size: CGSize = CGSize(width: 1,height: 1)) -> UIImage {
        var rect = CGRectMake(0, 0, size.width, size.height)
        UIGraphicsBeginImageContextWithOptions(size, false, 0)
        color.setFill()
        UIRectFill(rect)
        var image: UIImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }


}

这里有一个不使用任何图像的方法，这是唯一适合我的方法:

self.navigationController.navigationBar.layer.shadowOpacity = 0;

不幸的是，您需要在每个不希望出现该行的文件上执行此操作。在appDelegate中没有办法这样做。

编辑:

设置shadowColor为nil是不需要的，这是你唯一需要的行。