How do I change background color of UITabItem when item is selected

Question

I would like a different background color when the user selects a tab bar item than when it is unselected.

Answer 1

UPDATE: As of iOS 7.1 this technique no longer works (if the user taps the same tab twice in succession, the background colour is cleared).

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UITabBarItem is a subclass of UIBarItem, everything is more painful because UIBarItem doesn't subclass UIView; however, UITabBarItem contains one. What follows manipulates that view, and therefore might be rejected if submitted to the AppStore.

1) Subclass UITabBarItem

Create a subclass of UITabBarItem and add a new selected property to its header, like so:

@interface ALDTabBarItem : UITabBarItem
@property (nonatomic, assign, getter = isSelected) BOOL selected;
@end

UITabBarItems have a view property, but it isn't exposed. We can extend the class to access it, and then create a custom setter on the selected property to change the background colour, like so:

#import "ALDTabBarItem.h"

@interface ALDTabBarItem (ALD)
@property (nonatomic, strong) UIView *view;
@end

@implementation ALDTabBarItem

- (void)setSelected:(BOOL)selected
{
    if(selected)
        self.view.backgroundColor = [UIColor redColor];
    else
        self.view.backgroundColor = [UIColor clearColor];
} 

@end

2) Update your UITabBarController delegate

Add the following code to the delegate of your UITabBarController, which sets the selected states of the UITabBar:

- (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item
{
    for(ALDTabBarItem *myItem in tabBar.items)
        myItem.selected = (myItem == item);
}