Shadow UIview和clipsToBounds

Question

我想将阴影设置为我的容器UIView。我使用下面的代码来实现：

- (id)initWithCoder:(NSCoder*)aDecoder
{
    self = [super initWithCoder:aDecoder];
    if (self) {

        //-> drop shadow
        [self.layer setShadowColor:[UIColor blackColor].CGColor];
        [self.layer setShadowOpacity:0.6];
        [self.layer setShadowRadius:2.0];
        [self.layer setShadowOffset:CGSizeMake(2.0, 2.0)];
    }

    return self;
}

这样做效果很好。但是，当我在这个容器UIView上使用_containerView.clipsToBounds = YES;时，我看不到我的影子。为什么？

Answer 1

clipsToBounds还会剪辑您的阴影。为了防止这一点，你可以添加_containerView.layer.masksToBounds = NO，它禁止裁剪子层(参见更多here)。

Answer 2

如果您因为不希望子视图超出视图的边界而不得不使用clipsToBounds = true，但同时又需要在视图上添加阴影，我建议在视图后面添加一个额外的视图，并在额外的视图上设置阴影属性。

//run this in viewDidLoad() or your initialisation code
private func setupShadowContainer() {
    let containerShadow = UIView()
    parentView.addSubview(containerShadow)
    containerShadow.dropShadow()
    //using SnapKit here, you can use NSLayoutConstraint in a similar way to constraint the containerShadow behind your View
    containerShadow.snp.makeConstraints { (make) in
        make.edges.equalTo(yourView.snp.edges)
    }
}

//dropShadow method
extension UIView {
    func dropShadow() {
        self.translatesAutoresizingMaskIntoConstraints = false
        self.layer.shadowRadius = 3
        self.layer.shadowColor = UIColor.black.cgColor
        self.layer.shadowOffset = CGSize(width: 1.0, height: 1.0)
        self.layer.shadowOpacity = 0.5
        self.layer.masksToBounds = false
    }
}

Answer 3

下面是UIView扩展。

extension UIView {
    func addShadowAndRoundCorner(cornerRadius : CGFloat) {
        self.layer.shadowOffset = .zero
        self.layer.shadowOpacity = 0.5
        self.layer.shadowRadius = 3
        self.layer.shadowColor = UIColor.black.cgColor
        self.layer.masksToBounds = false
        self.layer.cornerRadius = cornerRadius
    }
}

在创建view后调用此函数，如下所示：

let roundView = UIView()
roundView.frame = CGRect.init(x: 0, y: 0, width: 100, height: 100)
roundView.addShadowAndRoundCorner(cornerRadius: 100/2)