inabox/InABox.Avalonia.Platform.iOS/ViewControllerHelper.cs

using UIKit;

public static class ViewControllerHelper
{
    public static UIViewController GetVisibleViewController()
    {
        var rootController = UIApplication.SharedApplication.KeyWindow?.RootViewController;

        if (rootController == null)
            return null;

        return GetTopViewController(rootController);
    }

    private static UIViewController GetTopViewController(UIViewController rootController)
    {
        if (rootController.PresentedViewController != null)
        {
            return GetTopViewController(rootController.PresentedViewController);
        }

        if (rootController is UINavigationController navigationController)
        {
            return GetTopViewController(navigationController.VisibleViewController);
        }

        if (rootController is UITabBarController tabBarController)
        {
            return GetTopViewController(tabBarController.SelectedViewController);
        }

        return rootController;
    }
}