ios - 以编程方式显示和隐藏 View Controller

Question

长期倾听者，第一次来电..

我正在尝试向我的应用程序添加一个横幅，该横幅将在没有网络连接时显示。我的应用程序使用大约 9 个 View Controller ，因此我认为 UIViewcontroller 的扩展将是明智的起点。我有一些逻辑来检查网络的运行状况，然后根据失败，它驱动NotificationCenter.post在当前显示器上显示viewController。此代码驻留在 UIViewController 扩展中，用于显示屏幕 - 它似乎起作用:

 func showNoNetworkBanner()
    {
        if let theMask = parent?.view.viewWithTag(666) {
            return  // already setted..
        } else {
            let maskView = UIView()
            maskView.tag = 666
            maskView.backgroundColor = UIColor.lightGray

            let vc = self.storyboard?.instantiateViewController(withIdentifier: "vc_NotNetworkWarning") as! vc_NotNetworkWarning
            maskView.addSubview(vc.view)
            parent?.view.addSubview(maskView)

        }
    }

另一方面，当 View Controller 出现时， View Controller 内会运行一些代码来查看运行状况是否正常。如果健康状况良好， View Controller 就会消失。在 View Controller 中，我几乎尝试了所有方法。当我使用这段代码时， View Controller 永远不会消失。

  let vc = parent?.view.viewWithTag(666)
    vc?.removeFromSuperview()

我尝试过的另一个变体是使用 .removeFrom ParentViewController() 并且 ViewController 确实消失了，但是我调用它的代码不起作用，因为 viewWithTag(666) 总是返回 true。

self.removeFromParentViewController()

有人可以帮我吗？有没有更好的方法在任何 View Controller 上显示单个“横幅”？

提前致谢!

Answer 1

晚上好。

根据您的问题，我假设您的网络连接检查正常工作。我将通过以下方式显示横幅:

1. 使用包含以下代码的新 .swift 文件创建横幅:

   class BannerViewLauncher: NSObject  {
   
       var viewController: UIViewController?
   
       lazy var bannerView : UIView = {
           let view = UIView(frame: .zero)
           view.backgroundColor = .lightGray
           return view
       }()
   
       //create more UIelements if you want to design the banner further. don't forget to add them as subviews to the bannerView and give them constraints.
   
       func showNoNetworkBanner() {
   
           if let window = UIApplication.shared.keyWindow {
   
               window.addSubview(bannerView)
   
               //define your desired size here (y position is out of view so it is off view by default, the y position will be changed when you call the showNoNetworkBanner() method.
               bannerView.frame = CGRect(x: 0, y: -100, width: window.frame.width, height: 100)
               //change withDuration if you want it to display slower or faster, just change all of them to the same for it so look good
               UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseInOut, animations: {
   
                   self.bannerView.frame = CGRect(x: 0, y: -100, width: window.frame.width, height: 100)
   
               }, completion: nil)
   
           }
       }
   
       func hideNoNetworkBanner() {
           if let window = UIApplication.shared.keyWindow {
           UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseIn, animations: {
   
                   self.bannerView.frame = CGRect(x: 0, y: -100, width: window.frame.width, height: 100)
   
           }, completion: nil)
           }
       }
   
   }
   

2. 在 ViewController 中，您希望显示 BannerViewLauncher 的这个(一个或多个)子类，并在 NoNetwork 观察者方法触发时调用该方法。

   lazy var bannerViewLauncher : BannerViewLauncher = {
       let launcher = BannerViewLauncher()
       launcher.viewController = self
       return launcher
   }()
   
   //call the following when you want the banner to display
   bannerViewLauncher.showNoNetworkBanner()
   
   //call this when you want to hide the banner
   bannerViewLauncher.hideNoNetworkBanner()
   

希望这能回答您的问题。