答复
建议添加UIView
navigationView = [[UIView alloc]initWithFrame:CGRectMake(X_BUFFER+5,Y_POS_BTN,self.view.frame.size.width-10,HEIGHT_BTN)];
navigationView.backgroundColor = [UIColor whiteColor];
[self.view addSubview:navigationView];
UIBezierPath *shadowPath = [UIBezierPath bezierPathWithRect:self.navigationView.bounds];
self.navigationView.layer.masksToBounds = NO;
self.navigationView.layer.shadowColor = [UIColor blackColor].CGColor;
self.navigationView.layer.shadowOffset = CGSizeMake(5.0f, 5.0f);
self.navigationView.layer.shadowOpacity = 0.8f;
self.navigationView.layer.shadowPath = shadowPath.CGPath;