Twitter-esque UITabBarController?

Question

I'd like to make an app that uses a UITabBarController that is similar to the one in the Twitter app for iPhone and iPod touch. (Blue light for unread and sliding arrow for switching between content views).

Is there an easy way to do this? Any open source code?

Edit:

I've added a bounty. I'm looking for an answer that works across devices and on iOS 4 and iOS 5.

EDIT:

I've messed with my original code and I found a simple solution. I've added the following check, for iOS 5 in my animation code:

//  iOS 5 changes the subview hierarchy 
//  so we need to check for it here

BOOL isUsingVersionFive = NO;
NSString *reqSysVer = @"5.0";
NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
if ([currSysVer compare:reqSysVer options:NSNumericSearch] != NSOrderedAscending){
    //On iOS 5, otherwise use old index
    isUsingVersionFive = YES;
}

Then, instead of this:

CGFloat tabMiddle = CGRectGetMidX([[[[self tabBar] subviews] objectAtIndex:index] frame]);

... I use this:

CGFloat tabMiddle = CGRectGetMidX([[[[self tabBar] subviews] objectAtIndex:index + (isUsingVersionFive ? 1 : 0)] frame]);

Still holding out on the bounty though, in case I get a chance to find something that works in the answers.

Answer 1

I would create a subclass of the standard UITabBarController and add a couple of subviews for the blue light and the sliding arrow. Shouldn't be too hard to accomplish.

Edit: Here's an idea of some of the stuff that should go in your subclass. I don't even know if this code will compile.

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {
        super.delegate = self;
    }
    return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];

    //Create blueLight
    UIImage* img = [UIImage imageNamed:@"blue_light.png"]
    self.blueLight = [[UIImageView alloc] initWithImage:img];
    self.blueLight.center = CGPointMake(320, 460); //I'm using arbitrary numbers here, position it correctly
    [self.view addSubview:self.blueLight];
    [self.blueLight release];

    //Create arrow, similar code.
}

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController{
    //Put code here that moves (animates?) the blue light and the arrow


    //Tell your delegate, what just happened.
    if([myDelegate respondsToSelector:@selector(tabBarController:didSelectViewController:)]){
        [myDelegate tabBarController:self didSelectViewController:viewController]
    }
}

Answer 2

Here is how you create the arrow

http://isagoksu.com/2009/development/iphone/fancy-uitabbar-like-tweetie/

And follow Rafael's answer to get the blue light.