把navigationController.navigation

- (void)viewWillAppear:(BOOL)animated{

    [super viewWillAppear:YES];

    [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"head_bar_pink_.png"] forBarMetrics:UIBarMetricsDefault];

    [self.navigationController.navigationBar setShadowImage:[self createImageWithColor:[UIColor clearColor]]];
}

//用颜色值创建图片

- (UIImage *)createImageWithColor:(UIColor *)color{

    CGRect rect = CGRectMake(0.0f,0.0f,1.0f,1.0f);

    UIGraphicsBeginImageContext(rect.size);

    CGContextRef context =UIGraphicsGetCurrentContext();

    CGContextSetFillColorWithColor(context, [color CGColor]);

    CGContextFillRect(context, rect);

    UIImage *theImage =UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return theImage;

}