在UIAlertController下的最高级UIAlertController

Question

我使用下面的扩展来查找top most ViewController。如果出现警报，则上面的代码将给出UIAlertController。如何在 UIAlertController下获得顶部视图控制器UIAlertController

Answer 1

创建一个如下所示的UIApplication扩展，UIApplication.topViewController()将返回UIAlertController下最顶部的UIViewController

iOS 13+

extension UIApplication {

    class func topViewController(controller: UIViewController? = UIApplication.shared.windows.first?.rootViewController) -> UIViewController? {
        if let navigationController = controller as? UINavigationController {
            return topViewController(controller: navigationController.visibleViewController)
        }
        if let tabController = controller as? UITabBarController {
            if let selected = tabController.selectedViewController {
                return topViewController(controller: selected)
            }
        }
        if let presented = controller?.presentedViewController {
            return topViewController(controller: presented)
        }
        if let alert = controller as? UIAlertController {
            if let navigationController = alert.presentingViewController as? UINavigationController {
                return navigationController.viewControllers.last
            }
            return alert.presentingViewController
        }
        return controller
    }

}

iOS 12-

extension UIApplication {

    class func topViewController(controller: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -> UIViewController? {
        if let navigationController = controller as? UINavigationController {
            return topViewController(controller: navigationController.visibleViewController)
        }
        if let tabController = controller as? UITabBarController {
            if let selected = tabController.selectedViewController {
                return topViewController(controller: selected)
            }
        }
        if let presented = controller?.presentedViewController {
            return topViewController(controller: presented)
        }
        if let alert = controller as? UIAlertController {
            if let navigationController = alert.presentingViewController as? UINavigationController {
                return navigationController.viewControllers.last
            }
            return alert.presentingViewController
        }
        return controller
    }

}

Answer 2

您可以检查下一个viewController是否为UIAlertController，如果是，则返回它的父级。就像这样：

if let presented = base as? UIAlertController {
  return base.presentingViewController
}

在返回前使用的扩展名中添加此内容。

更新的

extension UIApplication {
   class func topViewController(base: UIViewController? =    (UIApplication.sharedApplication().delegate as! AppDelegate).window?.rootViewController) -> UIViewController? {
      if let nav = base as? UINavigationController {
         return topViewController(base: nav.visibleViewController)
      }
      if let tab = base as? UITabBarController {
         if let selected = tab.selectedViewController {
             return topViewController(base: selected)
         }
      }
      if let presented = base?.presentedViewController {
         return topViewController(base: presented)
      }

      if let alert = base as? UIAlertController {
         return alert.presentingViewController
      }

      return base
   }
}

Answer 3

可以使用UIAlertController的presentingViewController属性获取它的父控制器。

extension UIApplication {
  class func topViewController(base: UIViewController? = (UIApplication.sharedApplication().delegate as! AppDelegate).window?.rootViewController) -> UIViewController? {
    if let nav = base as? UINavigationController {
      return topViewController(base: nav.visibleViewController)
    }
    if let tab = base as? UITabBarController {
      if let selected = tab.selectedViewController {
        return topViewController(base: selected)
      }
    }
    if let alert = base as? UIAlertController {
      if let presenting = alert.presentingViewController {
        return topViewController(base: presenting)
      }
    }
    if let presented = base?.presentedViewController {
      return topViewController(base: presented)
    }
    return base
  }
}

在代码中使用这些更改，而不是在XCode上进行测试。