导航栏设置阴影

    /**设置导航栏阴影*/
    //设置阴影颜色
    self.navigationController.navigationBar.layer.shadowColor = [UIColor redColor].CGColor;
    //设置阴影偏移范围
    self.navigationController.navigationBar.layer.shadowOffset = CGSizeMake(0, 5);
    //设置阴影透明度
    self.navigationController.navigationBar.layer.shadowOpacity = 0.2;
    //设置阴影半径
    self.navigationController.navigationBar.layer.shadowRadius = 15;
    //设置阴影路径
    self.navigationController.navigationBar.layer.shadowPath = [UIBezierPath bezierPathWithRect:self.navigationController.navigationBar.bounds].CGPath;