根控制器

FifthViewController *five = [[FifthViewController alloc]init];

UINavigationController *nav5 = [[UINavigationController alloc]initWithRootViewController:five];

nav5.tabBarItem = [[UITabBarItem alloc]initWithTitle:@"下载管理" image:[UIImage imageNamed:@"7.png"] tag:5];

UITabBarController *tabBar = [[UITabBarController alloc]init];

//设置tabbar的子控制器

tabBar.viewControllers = [NSArray arrayWithObjects:nav1,nav2,nav3,nav4,nav5, nil];

tabBar.delegate = self;

[self.view addSubview:tabBar.view];