调用rootViewController

Question

我对Swift比较新 试图使用peek和pop previewActionItems＆＃34;编辑＆＃34;在编辑模式下打开SpeciesDetailViewController。有一个问题试图让segue呈现SpeciesDetailViewController并收到错误消息"Warning: Attempt to present SpeciesDetailViewController whose view is not in the window hierarchy"。我实施了Jacob Davis＆＃39; found here上的解决方案。

这修复了窗口层次结构错误，但是当调用SpeciesDetailViewController控制器时，导航控制器和tabBarController都不显示。

虽然我认为这是由于被调用为顶级viewController的SpeciesDetailViewController引起的，但我对如何修复它感到茫然。

你能帮我看一下导航控制器和tabBarController吗？

以下是我目前的代码：

主视图控制器

func showDetailsViewController() {

    let topVC = topMostController()
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let vc = storyboard.instantiateViewController(withIdentifier: "SpeciesDetailViewController") as! SpeciesDetailViewController
    topVC.present(vc, animated: true, completion: nil)

}

func topMostController() -> UIViewController {
    var topController: UIViewController = UIApplication.shared.keyWindow!.rootViewController!
    while (topController.presentedViewController != nil) {
        topController = topController.presentedViewController!
    }

    return topController
}

Answer 1

对于UITabBarController和UINavigationController，您需要一个不同的实现。

这是我用来获取topMostViewController的代码：

protocol TopUIViewController {
    func topUIViewController() -> UIViewController?
}

extension UIWindow : TopUIViewController {
    func topUIViewController() -> UIViewController? {
        if let rootViewController = self.rootViewController {
            return self.recursiveTopUIViewController(from: rootViewController)
        }

        return nil
    }

    private func recursiveTopUIViewController(from: UIViewController?) -> UIViewController? {
        if let topVC = from?.topUIViewController() { return recursiveTopUIViewController(from: topVC) ?? from }
        return from
    }
}

extension UIViewController : TopUIViewController {
    @objc open func topUIViewController() -> UIViewController? {
        return self.presentedViewController
    }
}

extension UINavigationController {
    override open func topUIViewController() -> UIViewController? {
        return self.visibleViewController
    }
}

extension UITabBarController {
    override open func topUIViewController() -> UIViewController? {
        return self.selectedViewController ?? presentedViewController
    }
}

现在你可以使用它来从你的应用程序中获取topUIViewController，而不管你有什么UIViewController堆栈，包括UINavigationController，UITabBarViewController。

let topVC = UIApplication.shared.keyWindow!.rootViewController!.topUIViewController()