自定义tabbar，点击中间按钮不切换页面，而是让当前的子视图控制器跳转到新页面。（类似新浪微博发布）

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.delegate = self;
    /************************隐藏tabbar上的黑色线条***************************/
    CGRect rect = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]);
    CGContextFillRect(context, rect);
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    [self.tabBar setBackgroundImage:img];
    [self.tabBar setShadowImage:img];
    /************************隐藏tabbar上的黑色线条***************************/

    
    UITabBarItem *item1 = [[UITabBarItem alloc]initWithTitle:@"首页" image:[[UIImage imageNamed:@"tabbar_home"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] tag:0];
    item1.selectedImage = [[UIImage imageNamed:@"tabbar_home_selected"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    UITabBarItem *item2 = [[UITabBarItem alloc]initWithTitle:@"" image:[[UIImage imageNamed:@"tabbar_order"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] tag:0];
    UITabBarItem *item3 = [[UITabBarItem alloc]initWithTitle:@"我的" image:[[UIImage imageNamed:@"tabbar_person"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] tag:0];
    item3.selectedImage = [[UIImage imageNamed:@"tabbar_person_selected"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];

    
    NSArray *controllers = @[@"HomePage",@"Order",@"Person"];
    for (int i = 0; i < 3; i++) {
        Class cls = NSClassFromString([NSString stringWithFormat:@"%@ViewController",controllers[i]]);
        UIViewController *controller = (UIViewController *)[[cls alloc] init];
        UINavigationController *nc = [[UINavigationController alloc] initWithRootViewController:controller];
        nc.tabBarItem = @[item1,item2,item3][i];
        [self addChildViewController:nc];
    }
    
    
    UIImageView *tabbarView = [[UIImageView alloc] initWithFrame:CGRectMake(0, self.tabBar.frame.size.height - 61, SCREEN_WIDTH, 61)];
    tabbarView.image = [UIImage imageNamed:@"tabbar"];
    [self.tabBar addSubview:tabbarView];
    
}

- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController {
    if (viewController == self.viewControllers[1]) {
        //点击中间tabbarItem，不切换，让当前页面跳转
        OrderViewController *order = [[OrderViewController alloc] init];
        order.hidesBottomBarWhenPushed = YES;
        [(UINavigationController *)tabBarController.selectedViewController pushViewController:order animated:YES];
        return NO;
    }
    return YES;
}