Question

我需要对状态和导航栏全局应用渐变，并使其适应方向变化。因为我希望这是全局的，所以我尝试使用UIAppearance。令人惊讶的是，UIAppearance并不容易做到。

在“人像”中看起来很棒，但是在“风景”中时渐变太大，因此您看不到整个东西：

这是我的代码：

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    let navigationBarAppearance = UINavigationBar.appearance()
    navigationBarAppearance.titleTextAttributes = [NSAttributedString.Key.foregroundColor: UIColor.white]
    navigationBarAppearance.isTranslucent = false
    navigationBarAppearance.tintColor = UIColor.white

    let status_height = UIApplication.shared.statusBarFrame.size.height
    let gradientLayer = CAGradientLayer(frame: CGRect(x: 0, y: 0, width: 64, height: status_height + 44), colors: [UIColor.init(hex: "005382"), UIColor.init(hex: "00294B")])
    let layerImage = gradientLayer.createGradientImage()
    navigationBarAppearance.barTintColor = UIColor(patternImage: layerImage ?? UIImage())
}

我正在使用此扩展程序：

extension CAGradientLayer {
  convenience init(frame: CGRect, colors: [UIColor]) {
    self.init()
    self.frame = frame
    self.colors = []
    for color in colors {
      self.colors?.append(color.cgColor)
    }
    startPoint = CGPoint(x: 0, y: 0)
    endPoint = CGPoint(x: 0, y: 1)
  }

  func createGradientImage() -> UIImage? {

    var image: UIImage? = nil

    UIGraphicsBeginImageContext(bounds.size)

    if let context = UIGraphicsGetCurrentContext() {
      render(in: context)
      image = UIGraphicsGetImageFromCurrentImageContext()
    }

    UIGraphicsEndImageContext()

    return image
  } 
}

我知道我可以检查方向，然后相应地更改渐变，但是我需要在每个视图控制器上执行此操作，以免破坏使用UIAppearance并能够在一处完成的目的

我发现大多数SO线程都提供了在视图控制器级别（而不是全局级别）上进行顶部栏渐变的解决方案。

编辑：在我的UITabBarController上尝试了@Pan Surakami的答案，但我仍然有白色导航栏：

这是我的Storybaord设置：

和代码：

class MenuTabBarController: UITabBarController {
    var notificationsVM = NotificationsVModel()
    var hasNewAlerts: Bool = false

    override func viewDidLoad() {
      super.viewDidLoad()

      setTabs()

      styleUI()

      notificationsVM.fetchData { (success, newNotifications) in
            if success {
                self.hasNewAlerts = newNotifications.count > 0 ? true : false
                DispatchQueue.main.async {
                    if let tabBarItems = self.tabBar.items {
                        for (_, each) in tabBarItems.enumerated() {
                            if each.tag == 999 { //only update the alerts tabBarItem tag == '999'
                                self.updateAlertBadgeIcon(self.hasNewAlerts, each)
                            }
                        }
                    }
                }
            }
        }
    }

  fileprivate func setTabs() {
    let tab1 = GradientNavigationController(rootViewController: FeedViewController())
    let tab2 = GradientNavigationController(rootViewController: NotificationsTableViewController())
    let tab3 = GradientNavigationController(rootViewController: SearchViewController())
    let tab4 = GradientNavigationController(rootViewController: ComposeDiscussionViewController())
    UITabBarController().setViewControllers([tab1, tab2, tab3, tab4], animated: false)
  }

    func updateAlertBadgeIcon(_ hasAlerts: Bool, _ item: UITabBarItem) {
        if hasAlerts {
            item.image = UIImage(named: "alert-unselected-hasAlerts")?.withRenderingMode(UIImage.RenderingMode.alwaysOriginal)
            item.selectedImage = UIImage(named: "alert-selected-hasAlerts")?.withRenderingMode(UIImage.RenderingMode.alwaysOriginal)
        } else {
            hasNewAlerts = false
            item.image = UIImage(named: "alert-unselected-noAlerts")?.withRenderingMode(UIImage.RenderingMode.alwaysOriginal)
            item.selectedImage = UIImage(named: "alert-selected-noAlerts")?.withRenderingMode(UIImage.RenderingMode.alwaysOriginal)
        }
    }

    // UITabBarDelegate
    override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem) {
        if item.tag == 999 { //alerts tabBarItem tag == '999'
            updateAlertBadgeIcon(hasNewAlerts, item)
        }
      if item.tag == 0 { //Feed Item clicked
        if let feedNav = children[0] as? UINavigationController, let feedVC = feedNav.viewControllers[0] as? FeedViewController {
          feedVC.tableView.reloadData()
        }

      }
    }

    func styleUI() {
        UITabBar.appearance().backgroundImage = UIImage.colorForNavBar(color:.lightGrey4)
        UITabBar.appearance().shadowImage = UIImage.colorForNavBar(color:.clear) 
        tabBar.layer.shadowOffset = CGSize.zero
        tabBar.layer.shadowRadius = 2.0
        tabBar.layer.shadowColor = UIColor.black.cgColor
        tabBar.layer.shadowOpacity = 0.30
        UITabBarItem.appearance().setTitleTextAttributes([NSAttributedString.Key.foregroundColor : UIColor.grey2,
                                                          NSAttributedString.Key.font: UIFont(name: "AvenirNext-DemiBold", size: 12) as Any],
                                                         for: .normal)
        UITabBarItem.appearance().setTitleTextAttributes([NSAttributedString.Key.foregroundColor : UIColor.darkSapphire,
                                                          NSAttributedString.Key.font: UIFont(name: "AvenirNext-DemiBold", size: 12) as Any],
                                                         for: .selected)
    }
}

Answer 1

一种实现方法是子类UINavigationController。

创建一个新的子类。

class GradientNavigationController: UINavigationController {}

覆盖traitCollectionDidChange方法。

class GradientNavigationController: UINavigationController {
    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)

        let status_height = UIApplication.shared.statusBarFrame.size.height
        let gradientLayer = CAGradientLayer(frame: CGRect(x: 0, y: 0, width: 64, height: status_height + 44), colors: [[UIColor.init(hex: "005382"), UIColor.init(hex: "00294B")])
        let layerImage = gradientLayer.createGradientImage()
        self.navigationBar.barTintColor = UIColor(patternImage: layerImage ?? UIImage())
    }
}

使用此子类代替UINavigationController。可以在Storiboard上更改自定义子类，或者在代码中使用它。

编辑：您的UITabBarController由情节提要配置。因此，setTabs()以这种方式使用是没有意义的。它只是创建UITabBarController的另一个副本，然后将其删除。我将其作为嵌入控制器的示例进行了展示。

删除方法setTabs()。
打开每个链接到您的标签的故事板。（我看不到它们是如何配置的，它们位于情节提要引用的后面。）
确保初始控制器为GradientNavigationController。

enter image description here

全局将渐变应用于导航栏并处理方向更改

1 个答案: