Changing Done button with image on Model View

[bishalg]

I have following code to display the model view of SVWevViewController but I cant see the change on SVView DONE button ? why ?

NSString *linkURL = [[[self allItems] objectAtIndex:[self itemNo]] valueForKey:@"link"];

UIImage *buttonImage = [UIImage imageNamed:@"btn_left"];
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
[button setImage:buttonImage forState:UIControlStateNormal];
button.frame = CGRectMake(0, 0, buttonImage.size.width, buttonImage.size.height);
[button addTarget:self action:@selector(backAction) forControlEvents:UIControlEventTouchUpInside];
UIBarButtonItem *customBarItem = [[UIBarButtonItem alloc] initWithCustomView:button];

SVModalWebViewController *webViewController = [[SVModalWebViewController alloc] initWithAddress:linkURL];
webViewController.navigationItem.leftBarButtonItem = customBarItem;

[self presentModalViewController:webViewController animated:YES];