Custom back button disappears after setting navigation bar background image - iphone

Question

I'm using the following categories code to change
the background image of the navigation bar
#import <Foundation/Foundation.h>
#interface UINavigationBar (CustomImage)
- (void) setBackgroundImage:(UIImage*)image;
- (void) clearBackgroundImage;
#end
#import "UINavigationBar+CustomImage.h"
#implementation UINavigationBar (CustomImage)
- (void) setBackgroundImage:(UIImage*)image {
if (image == NULL) return;
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
imageView.frame = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
[self insertSubview:imageView atIndex:0];
[imageView release];
}
- (void) clearBackgroundImage {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSArray *mySubviews = [self subviews];
for (int i = [mySubviews count] - 1; i >= 0; i--)
{
if ([[mySubviews objectAtIndex:i] isMemberOfClass:[UIImageView class]])
{
[[mySubviews objectAtIndex:i] removeFromSuperview];
return;
}
}
[pool release];
}
#end
And i'm using the following code to generate the custom back button
in my view
UIButton *btnBack = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
[btnBack addTarget:self action:#selector(goBack) forControlEvents:UIControlEventTouchUpInside];
[btnBack setImage:[UIImage imageNamed:#"back.png"] forState:UIControlStateNormal];
UIBarButtonItem *barBtnBack = [[UIBarButtonItem alloc] initWithCustomView:btnBack];
self.navigationItem.leftBarButtonItem = barBtnBack;
[btnBack release];
[barBtnBack release];
But the button most of the time is hidden under the bg image
and some times it randomly appears.
Why is this happening? I'm not sure what's the problem the image is inserted at index 0
so as I understand it is supposed to be behind all the time.
Please help.

Answer 1

Try the following code to change background of the navigation bar in the class where you are loading the navigation bar.
#interface UINavigationBar (MyCustomNavBar)
#end
#implementation UINavigationBar (MyCustomNavBar)
- (void) drawRect:(CGRect)rect
{
UIImage *barImage = [UIImage imageNamed:#"image.png" ];
[barImage drawInRect:rect];
}
#end

Answer 2

Using the method Praveen S suggested you could have a global variable for the next background image name and set it in your viewDidLoad method, then in your draw rect method use the imageName stored in the variable rather than hardcoding it in the draw rect.

Answer 3

You should try creating the button after adding the image.