view的周围阴影设置

 UIView *shadowView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, self.xs_width, self.xs_height)];
    shadowView.backgroundColor = [UIColor whiteColor];
    shadowView.layer.cornerRadius = 7.f;
    shadowView.layer.shadowOffset = CGSizeMake(0, 1.5);
    shadowView.layer.shadowRadius = 5.0f;
    shadowView.layer.shadowOpacity = 1;
    shadowView.layer.shadowColor = [UIColor colorWithHex:0xdddddd].CGColor;
    
    [self addSubview:shadowView];
    [shadowView mas_updateConstraints:^(MASConstraintMaker *make) {
        make.edges.equalTo(self);
    }];