How to Customize UITabBar on iOS 5

Building the new version of the app Blocos de Rua I was challenged to customize the UITabBar so it meets what the designer wants. In iOS 5 this is pretty easy to do but I haven’t figured out the proper way to do it from the beginning, this post is my findings on how to do it properly by correctly using the new iOS 5 APIs to customize appearance.

The final look:

Keep reading to see the code.

The appearance APIs in iOS 5 are great. They reduce lots of custom drawRect: that used to be necessary to customize the default UIKit components. The first time I tried to customized the tab bar I had some problems with images been offset upwards because I was using the wrong methods.First thing I learned, the setFinishedSelectedImage:finishedUnselectedImage: from UITabBarItem is the tab’s icon not a image for the whole tab with background, icon and label.

Customize the UITabBar is a peace of cake when you understand how the APIs should be used, take a look:

From inside out, the UITabBar

First - usually in your app delegate - set the image for the entire tab bar’s background, which represents the “normal” state of all tabs. The dimension is 320 x 49 points.

[[[self tabBarController] tabBar] setBackgroundImage:[UIImage imageNamed:@"background"]];

Then configure the selected state of a tab. This is necessary because in this app I don’t want the default white highlight that represents the selected tab. Pay attention to the image’s width, it must be the same of a single tab. In my case 320/4, 80 points wide.

[[[self tabBarController] tabBar] setSelectionIndicatorImage:[UIImage imageNamed:@"selected"]];

Last but not least, the UITabBarItem

Unlike the default behavior the image shouldn’t change when the tab is selected, this is why I set the same image in both states. For each UIViewController that will be part of the tab bar you need to configure the tab image like this:

- (id)init {
    self = [super initWithNibName:@"MyNibName" bundle:nil];
    if (self) {
        self.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"The Title" image:nil tag:0];
        [[self tabBarItem] setFinishedSelectedImage:[UIImage imageNamed:@"tab_icon"] withFinishedUnselectedImage:[UIImage imageNamed:@"tab_icon"]];
    }
}

The last detail is the title’s color on the unselected tab, they can’t be the default gray color. To change the color we need a dictionary of attributes whit the  UITextAttributeTextColor  key:

// below the setFinishedSelectedImage:withFinishedUnselectedImage:
[[self tabBarItem] setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:
        [UIColor whiteColor], UITextAttributeTextColor,
        nil] forState:UIControlStateNormal];

That’s all folks.

转帖：http://felipecypriano.com/2012/02/27/how-to-customize-uitabbar-on-ios-5/