How to make an animation of "cancel" button when touch the UITextField - ios

Question

I am now creating an App that has a browser like Safari:
There is a UITextField(left side) and UISearchBar(right side) inserted into the UINavigationBar on the top of the view.
I am wondering if there is a way to add an animation on a "Cancel" button at the time it appears when user touches the UITextField.
The animation is just like it is on the Safari: when User touches the UITextField, the "Cancel" button comes from right outside of the window while the UISearchBar is fading.
Note that I am initializing the "Cancel" button by UIBarbuttonItem(UIBarButtonSystemItemCancel).
Any help would be appreciated.
Update:
Finally I found the anwser by myself. It seems that you cannot assign a specific position where UIBarButtonItem shows up or hide. So one possible way to solve this problem is to customize a UIButton just looks like the UIBarButtonItem, here is the code:
-(void)viewDidLoad {
......
CGSize backgroundStretchPoints = {4, 2};
UIImage *image = [[UIImage imageNamed:#"UINavigationBarDefaultButton.png"] stretchableImageWithLeftCapWidth:backgroundStretchPoints.width
topCapHeight:backgroundStretchPoints.height];
button = [UIButton buttonWithType:UIButtonTypeCustom];
button.frame = CGRectMake(330, 23, 80, 30); // initialize the button outside the window
[button setBackgroundImage:image forState:UIControlStateNormal];
[button setTitle:#"Cancel" forState:UIControlStateNormal];
button.titleLabel.font = [UIFont fontWithName:#"Helvetica-Bold" size:12];
[button addTarget:self action:#selector(cancelButtonPressed) forControlEvents:UIControlEventTouchUpInside];
[navigationBar addSubview: button];
.......
}
and when you click the UITextField(i.e.), the cancel button will slide into the window:
-(void)textFieldDidBeginEditing:(UITextField *)textField {
[UIView animateWithDuration:0.25 animations:^{
button.frame = CGRectMake(232, 23, 80, 30); // here is the position button will slide into window with animation
}];
}