不论中间采用了 push->push->present还是present->push->present都可以准确的获取到正在显示的控制器。
//获取当前所展示的控制器

- (UIViewController *)theTopviewControler{
    //获取根控制器
    UIViewController *rootVC = [[UIApplication sharedApplication].delegate window].rootViewController;
    
    UIViewController *parent = rootVC;
    //遍历 如果是presentViewController
    while ((parent = rootVC.presentedViewController) != nil ) {
        rootVC = parent;
    }
   
    while ([rootVC isKindOfClass:[UINavigationController class]]) {
        rootVC = [(UINavigationController *)rootVC topViewController];
    }
    return rootVC;
}