Can't change the background for UIBarButtonItem - ios

Question

I need to change the default (which was already declared in my AppDelegate) background for UIBarButtonItem in one ViewController.
So, In my AppDelegate I have:
UIImage *navBarItemBackground = [UIImage imageNamed:#"navbar_button_green"];
[[UIBarButtonItem appearance] setBackgroundImage:navBarItemBackground
forState:UIControlStateNormal
style:UIBarButtonItemStyleBordered
barMetrics:UIBarMetricsDefault];
And when I need to restore the default background for the button - I implement in my viewController:
self.navigationItem.rightBarButtonItem = nil;
UIBarButtonItem *rightBarItem = [[UIBarButtonItem alloc] initWithTitle:#"Сохранить" style:UIBarButtonItemStyleBordered target:self action:#selector(clickOnSend:)];
[rightBarItem setBackgroundImage:[UIImage imageNamed:#""] forState:UIControlStateNormal style:UIBarButtonItemStyleBordered barMetrics:UIBarMetricsDefault];
self.navigationItem.rightBarButtonItem = rightBarItem;
But I think that it's not correct to set the empty file as the image. Is there more simple way to implement this behaviour? Thanks!

Answer 1

If you want to change only one or several UIViewController's UIBarButtonItems backgroundImage, you'd better change in the specific UIViewControllers as the latter case you use. while [[UIBarButtonItem appearance] setBackgroundImage:forState:style:barMetrics:]; will change all the UIBarButtonItems background image, which maybe not the better one.

Answer 2

You should change your code to this:
UIBarButtonItem * rightBarItem = [[UIBarButtonItem alloc]
initWithTitle: #"Сохранить"
style: UIBarButtonItemStyleBordered
target: nil action: nil];
UIImage *navBarItemBackground = [[UIImage imageNamed:#"navbar_button_green"]resizableImageWithCapInsets:UIEdgeInsetsMake(0, 13, 0, 6)];
[[UIBarButtonItem appearance] setBackgroundImage:navBarItemBackground
forState:UIControlStateNormal
barMetrics:UIBarMetricsDefault];
[self.navigationItem setBackBarButtonItem: rightBarItem];