Custom button in tabbar problem - iphone

Question

I've a TabBarController Application.
This code in didFinishingLaunching method:
UIImage *buttonImage = [UIImage imageNamed:#"post-button2.png"];
UIButton* button = [UIButton buttonWithType:UIButtonTypeCustom];
NSLog(#"Button size: %f, %f", buttonImage.size.width, buttonImage.size.height);
button.frame = CGRectMake(0.0, 0.0, buttonImage.size.width, buttonImage.size.height);
[button setBackgroundImage:buttonImage forState:UIControlStateNormal];
CGFloat heightDifference = buttonImage.size.height - self.tabBarController.tabBar.frame.size.height;
NSLog(#"self.tabBarController.tabBar.frame.size.height: %f", self.tabBarController.tabBar.frame.size.height);
NSLog(#"heightDifference: %f", heightDifference);
NSLog(#"%Tabbar: %f, %f", tabBarController.tabBar.center.x, tabBarController.tabBar.center.y);
if (heightDifference < 0)
button.center = tabBarController.tabBar.center;
else {
CGPoint center = self.tabBarController.tabBar.center;
center.y = center.y - heightDifference/2.0;
button.center = tabBarController.tabBar.center;
}
NSLog(#"%Button: %f, %f", button.center.y, button.center.x);
[tabBarController.view addSubview:button];
[self.window addSubview:tabBarController.view];
[self.window makeKeyAndVisible];
The output is:
Where is the problem? I can solve with hardcoded code:
CGPoint center = tabBarController.tabBar.center;
center.x = 160.00;
center.y = 455.50;
button.center = center;
But I'm not sure that is correct.
Ty.

Answer 1

To set the image of a tab you need to set the tabBarItem of the viewcontroller associated with the tab.
See UITabBarItem ref for how to create one with custom image.
So you create a UITabBarItem object with the custom image and then make it the tabBarItem property of the viewcontroller for the tab.
The UITabBarController will then manage putting the image in the right place.