UINavigationBar在AppDelegate.swift中設置自定義陰影

Question

我想在整個應用程序的UINavigationBar底部設置一些陰影。 這是我嘗試過但它不起作用：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    UINavigationBar.appearance().layer.shadowOffset = CGSizeMake(0, 3)
    UINavigationBar.appearance().layer.shadowRadius = 3.0
    UINavigationBar.appearance().layer.shadowColor = UIColor.yellowColor().CGColor
    UINavigationBar.appearance().layer.shadowOpacity = 0.7
}

請告訴我該怎么做？

更新：通過UINavigationController的子類化解決

import UIKit

class ShadowUINavigationController: UINavigationController {

    override func viewWillAppear(animated: Bool) {
        let darkColor: CGColorRef = UIColor(hex: 0x212121).CGColor
        let lightColor: CGColorRef = UIColor.clearColor().CGColor
        let navigationBarBottom: CGFloat = self.navigationBar.frame.origin.y + self.navigationBar.frame.size.height + 20
        println(self.navigationBar.frame.origin.y)
        println(self.navigationBar.frame.size.height)
        println(navigationBarBottom)

        let newShadow: CAGradientLayer = CAGradientLayer()
        newShadow.frame = CGRectMake(0, navigationBarBottom, self.view.frame.size.width, 1)
        newShadow.colors = [darkColor, lightColor]
        self.view.layer.addSublayer(newShadow)
        super.viewWillAppear(animated)
    }
}

Answer 1

仍然使用外觀並且不要求您將UINavigationBar子類化並向每個導航控制器添加代碼的更好解決方案是：

擴展UINavigationBar

extension UINavigationBar {

  var castShadow : String {
    get { return "anything fake" }
    set {
        self.layer.shadowOffset = CGSizeMake(0, 3)
        self.layer.shadowRadius = 3.0
        self.layer.shadowColor = UIColor.yellowColor().CGColor
        self.layer.shadowOpacity = 0.7

    }
  }

}

並添加應用程序范圍外觀規則（例如在appdelegate“didFinishLaunchingWithOptions”內）

UINavigationBar.appearance().castShadow = ""

Answer 2

簡單，適用於Swift 3：

    navigationController?.navigationBar.layer.shadowColor = UIColor.black.cgColor
    navigationController?.navigationBar.layer.shadowOpacity = 1
    navigationController?.navigationBar.layer.shadowOffset = CGSize.zero
    navigationController?.navigationBar.layer.shadowRadius = 10