UINavigationBar去渐变
@implementation UINavigationBar (CustomBackground)

- (UIImage *)barBackground
{
return [UIImage imageNamed:@"login_nav_bg.png"];
}

- (void)didMoveToSuperview
{
//iOS5 only
if ([self respondsToSelector:@selector(setBackgroundImage:forBarMetrics:)])
{
[self setBackgroundImage:[self barBackground] forBarMetrics:UIBarMetricsDefault];
}
}

//this doesn't work on iOS5 but is needed for iOS4 and earlier
- (void)drawRect:(CGRect)rect
{
//draw image
[[self barBackground] drawInRect:rect];
}

@end