Setting shadowImage On Translucent Navigation Bar - iphone

Question

I am trying to set the shadowImage of the navigaion bar in my app delegate:
[[UINavigationBar appearance]setShadowImage:[UIImage imageNamed:#"navigation-bar-shadow"]];
This does not work by itself. It only works if I set the background image of the navigaion bar as well:
[[UINavigationBar appearance]setBackgroundImage:[UIImage new]forBarPosition:UIBarPositionAny barMetrics:UIBarMetricsDefault];
Here is my problem... the navigation bar is transluncent and I would like to keep it that way (no background images). But it seems that I cant set the shadowImage without setting the background image.
How can I set the shadowImage on translucent navigation bar?
Thanks!

Answer 1

Yes, you cannot set a shadowImage of a navigationBar without setting its backgroundImage :
See UINavigationBar Documentation :
For a custom shadow image to be shown, a custom background image must
also be set with the setBackgroundImage:forBarMetrics: method.
But you can render shadowImage invisible with empty image :
[[UINavigationBar appearance] setShadowImage:[[UIImage alloc ]init]];

Answer 2

The response marked as an answer does not work if you want to keep the translucent effect in the NavigationBar.
A workaround I did was:
1) Create an Image with the color I wanted:
CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [[UIColor blueColor] CGColor]);
CGContextFillRect(context, rect);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
Then I assigned this as the backgroundImage to the UINavigationBar
[[UINavigationBar appearance]setShadowImage:[[UIImage alloc] init]];
[[UINavigationBar appearance]setBackgroundImage:image forBarMetrics:UIBarMetricsDefault];
Note that this makes the navigation bar fully transparent. Then I did the following to mimic the translucent 'blur' effect:
UIView *obfuscateView = [[UIView alloc] initWithFrame:CGRectMake(0,0,64,self.view.frame.width)];
[obfuscateView setBackgroundColor:[UIColor blueColor]];
[obfuscateView setAlpha:0.9f];
[self.view addSubView:obfuscateView];
The main thing here is you need to now add an additional view behind the navigationBar that will mimic the blur effect. This can be achieved with a minimal hit to performance by playing with alpha transparency rather than actually doing the calculations using a blurring view. Also note that this UIView needs to be of the same color.
What this allows you to do though is also play with gradients that have varying alpha to create a fading effect into the nav bar.