实现一个简单的UITabBar:

AppDelegate.m

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



UILabel *lab = [[UILabel alloc]initWithFrame:CGRectMake(320/2-140/2, 80, 140, 40)];
lab.text = @"王振";
lab.textAlignment = UITextAlignmentCenter;
lab.backgroundColor = [UIColor blueColor];
[self.window addSubview:lab];

//your code
UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(320/2-140/2,480/2-40/2, 140, 40)];
label.text = @"Hello World";
label.backgroundColor = [UIColor cyanColor];
label.textAlignment = UITextAlignmentCenter;
[self.window addSubview:label];

HomeViewController *view1 = [[HomeViewController alloc]init];
UINavigationController *v1 = [[UINavigationController alloc]initWithRootViewController:view1];

MessageViewController *view2 = [[MessageViewController alloc]init];
UINavigationController *v2 = [[UINavigationController alloc]initWithRootViewController:view2];

SearchViewController *view3 = [[SearchViewController alloc]init];
UINavigationController *v3 = [[UINavigationController alloc]initWithRootViewController:view3];

SettingViewController *view4 = [[SettingViewController alloc]init];
UINavigationController *v4 = [[UINavigationController alloc]initWithRootViewController:view4];


//NSArray *arr = @[view1,view2,view3,view4];

NSArray *viewControllers = [NSArray arrayWithObjects:v1,v2,v3,v4 , nil];

UITabBarController *mainViewController = [[UITabBarController alloc]init];
mainViewController.viewControllers = viewControllers;
//[mainViewController setViewControllers:mainViewController];

//[mainViewController release];
[UIApplication sharedApplication].applicationIconBadgeNumber = 2;

[self.window setRootViewController:mainViewController];


return YES;
}

HomeViewController.m

<

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
self.title = @"首页";
self.tabBarItem.badgeValue = @"New";

}
return self;
}

-(void)loadView
{
UIView *view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
view.backgroundColor = [UIColor whiteColor];
self.view = view;

}

技巧：
给Iphone图标添加数字提示：self.tabBarItem.badgeValue = 8；