先登录 在跳转到tabBar

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

    
    // 第二步：创建UITabBarController对象
    self.mainTab = [[UITabBarController alloc] init];
    
    // 第三步：设置window的根视图控制器
    self.window.rootViewController = self.mainTab;
    UINavigationController *loginVC = [[UINavigationController alloc] initWithRootViewController:[[LoginViewController alloc] init]];
    loginVC.navigationBarHidden = YES;
    [self.mainTab presentViewController:loginVC animated:NO completion:nil];

    // 控制器
    UINavigationController *homeNVC = [[UINavigationController alloc] initWithRootViewController:[[HomeViewController alloc] init]];
    // 设置图片
    homeNVC.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"首页" image:[[UIImage imageNamed:@"tb_08"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"tb_09"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];
    
    UINavigationController *classNVC = [[UINavigationController alloc] initWithRootViewController:[[ClassifyViewController alloc] init]];
    // 设置图片
    classNVC.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"分类" image:[[UIImage imageNamed:@"tb_05"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"tb_03"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];
    
    UINavigationController *shoppingNVC = [[UINavigationController alloc] initWithRootViewController:[[ShoppingCarViewController alloc] init]];
    // 设置图片
    shoppingNVC.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"购物车" image:[[UIImage imageNamed:@"tb_06"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"tb_01"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];
    
    UINavigationController *userNVC = [[UINavigationController alloc] initWithRootViewController:[[UserViewController alloc] init]];
    // 设置图片
    userNVC.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"个人中心" image:[[UIImage imageNamed:@"tb_07"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] selectedImage:[[UIImage imageNamed:@"tb_02"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];
    
    // 将导航控制器对象添加到数组中
    self.mainTab.viewControllers = @[homeNVC,classNVC,shoppingNVC,userNVC];
    
    return YES;
}