iOS获取当前显示最顶层的ViewController

- (UIViewController*)currentViewController{
    UIViewController* vc = [UIApplication sharedApplication].keyWindow.rootViewController;
    while (true) {
        if ([vc isKindOfClass:[UINavigationController class]]) {
            vc = [(UINavigationController *)vc visibleViewController];
        } else if ([vc isKindOfClass:[UITabBarController class]]) {
            vc = [(UITabBarController *)vc selectedViewController];
        } else if (vc.presentedViewController) {
            vc = vc.presentedViewController;
        }else {
            break;
        }
    }
    return vc;
}