工程需要包含 QuartzCore.Framework。

//
//  UINavigationBar+JTDropShadow.h
//
//  Created by james on 9/20/11.
//  http://ioscodesnippet.tumblr.com
//
 
 
#import
 
@interface UINavigationBar (JTDropShadow)
 
- (void)dropShadowWithOffset:(CGSize)offset
                      radius:(CGFloat)radius
                       color:(UIColor *)color
                     opacity:(CGFloat)opacity;
 
 
@end
 
 
 
 
//
//  UINavigationBar+JTDropShadow.m
//
//  Created by james on 9/20/11.
//  http://ioscodesnippet.tumblr.com
//
 
 
#import "UINavigationBar+JTDropShadow.h"
 
#import
 
 
 
@implementation UINavigationBar (JTDropShadow)
 
- (void)dropShadowWithOffset:(CGSize)offset
                      radius:(CGFloat)radius
                       color:(UIColor *)color
                     opacity:(CGFloat)opacity {
 
    // Creating shadow path for better performance
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, self.bounds);
    self.layer.shadowPath = path;
    CGPathCloseSubpath(path);
    CGPathRelease(path);
 
    self.layer.shadowColor = color.CGColor;
    self.layer.shadowOffset = offset;
    self.layer.shadowRadius = radius;
    self.layer.shadowOpacity = opacity;
 
    // Default clipsToBounds is YES, will clip off the shadow, so we disable it.
    self.clipsToBounds = NO;
 
}
 
@end
 
 
//用法如下
 
- (void)viewDidLoad {
    [super viewDidLoad];
    ...
    [self.navigationController.navigationBar dropShadowWithOffset:CGSizeMake(0, 3)
                                                           radius:1
                                                            color:[UIColor darkGrayColor]
                                                          opacity:1];
    ...
}