How does the Twitter iPhone App animate the current tab bar indicator? http://idevrecipes.com/2010/12/17/twitter-app-tab-bar-animation/#comment-96

Landscape support

- (void) addTabBarArrow
{
	UIImage* tabBarArrowImage = [UIImage imageNamed:@"TabBarNipple.png"];
	self.tabBarArrow = [[[UIImageView alloc] initWithImage:tabBarArrowImage] autorelease];	
	CGRect frame = CGRectMake([self horizontalLocationFor:0], -4, [tabBarArrow frame].size.width, [tabBarArrow frame].size.height);
	[tabBarArrow setFrame:frame];
	[[tabBarController tabBar]  addSubview:tabBarArrow];

}

- (CGFloat) horizontalLocationFor:(NSUInteger)tabIndex
{
	UIDeviceOrientation deviceOrientation = [[UIDevice currentDevice] orientation];
	
	if (deviceOrientation == UIDeviceOrientationLandscapeRight || deviceOrientation == UIDeviceOrientationLandscapeLeft) {
		NSLog(@"land");
		// A single tab item's width is the entire width of the tab bar divided by number of items
		CGFloat tabItemWidth = 480 / tabBarController.tabBar.items.count;
		// A half width is tabItemWidth divided by 2 minus half the width of the arrow
		CGFloat halfTabItemWidth = (tabItemWidth / 2.0) - (tabBarArrow.frame.size.width / 2.0);
		
		// The horizontal location is the index times the width plus a half width
		return (tabIndex * tabItemWidth) + halfTabItemWidth;
	}else {
		NSLog(@"Portrait");
		// A single tab item's width is the entire width of the tab bar divided by number of items
		CGFloat tabItemWidth = 320 / tabBarController.tabBar.items.count;
		// A half width is tabItemWidth divided by 2 minus half the width of the arrow
		CGFloat halfTabItemWidth = (tabItemWidth / 2.0) - (tabBarArrow.frame.size.width / 2.0);
		
		// The horizontal location is the index times the width plus a half width
		return (tabIndex * tabItemWidth) + halfTabItemWidth;
		
	}
}

- (void)tabBarController:(UITabBarController *)theTabBarController didSelectViewController:(UIViewController *)viewController
{
	[UIView beginAnimations:nil context:nil];
	[UIView setAnimationDuration:0.2];
	CGRect frame = tabBarArrow.frame;
	frame.origin.x = [self horizontalLocationFor:tabBarController.selectedIndex];
	tabBarArrow.frame = frame;
	[UIView commitAnimations];  
	
}

- (void)application:(UIApplication *)application didChangeStatusBarOrientation:(UIInterfaceOrientation)oldStatusBarOrientation 
{
	NSLog(@"oi");
	[UIView beginAnimations:nil context:nil];
	[UIView setAnimationDuration:0.5];
	CGRect frame = tabBarArrow.frame;
	frame.origin.x = [self horizontalLocationFor:tabBarController.selectedIndex];
	tabBarArrow.frame = frame;
	[UIView commitAnimations];  
}