How to properly customize UITabBar and UITabBarItem on iOS 7 and iOS 8?

Question

I am googling around so much, but nowhere I find a straight and consolidated answer.

I want to customize myUITabBarController such tha

Answer 1

I had the same problem as you. As far as I know there is no difference for the different iOS versions.
I solved it programmatically like this:

1. Turning the bar color black works as following (You already said it) (in AppDelegate):

   UITabBar.appearance().barTintColor = UIColor.blackColor()

2. To set the color of the title for the different states, I used this code (in AppDelegate):

   UITabBarItem.appearance().setTitleTextAttributes([NSForegroundColorAttributeName!: UIColor.redColor()], forState:.Selected)
   UITabBarItem.appearance().setTitleTextAttributes([NSForegroundColorAttributeName!: UIColor.whiteColor()], forState:.Normal)
   

3. (and 4.) You can achieve the different item colors, multicolored icons and different item colors for the different states, by setting the image programmatically and change the rendering mode (imageWithRenderingMode:) to UIImageRenderingMode.AlwaysOriginal, this looks as following (do this in the first view controller class for all your view controllers):

   var recentsItem = self.tabBarController!.tabBar.items![0] as UITabBarItem
   var recentsItemImage = UIImage(named:"recents.png")!.imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)
   var recentsItemImageSelected = UIImage(named: "recentsSelected.png")!.imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)
   recentsItem.image = recentsItemImage
   recentsItem.selectedImage = recentsItemImageSelected
   

I hope this helps, if you have any following questions, feel free to ask me.

Answer 2

Solution provided by smudis is great and because I don't have enough reputation to comment I decided to post the 3rd part of smudis' solution in Objective-C, in case it might help somebody:

To get a reference of the tabBar type the above code into AppDelegate's method application:didFinishLaunchingWithOptions:

UITabBarController *tbc = (UITabBarController*)self.window.rootViewController;
UITabBar *tb = tbc.tabBar;

Then the image adjustment can be done as follows:

for (UITabBarItem *tbi in tb.items) {
    tbi.selectedImage = [tbi.selectedImage imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    tbi.image = [tbi.image imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
}