主要用到的、、

<UITabBarControllerDelegate, UITabBarDelegate>

self.delegate = self;

- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController {
    if (viewController == self.viewControllers[1]) {
        //点击第二个tabbarItem，不切换tab，直接跳转
        IODetectionViewController *order = [[IODetectionViewController alloc] init];
        order.hidesBottomBarWhenPushed = YES;
        [(UINavigationController *)tabBarController.selectedViewController pushViewController:order animated:YES];
        return NO;
    }
    return YES;
}