仅从 UIView 的 3 个侧面绘制阴影

Question

我已经成功地在我的UIView 周围画了一个阴影，如下所示：

block1.layer.masksToBounds = NO;
block1.layer.shadowOffset = CGSizeMake(0, 0);
block1.layer.shadowRadius = 1;
block1.layer.shadowOpacity = 0.7;

现在发生的事情是我有一个矩形UIView，我想在它的三个边上绘制阴影，留下它的 底部 边没有阴影.

我知道我必须通过创建一个新的UIBezierPath 来指定block1.layer.shadowPath，但我不知道该怎么做。

显然，设置 layer.shadowOffset 对我来说不起作用。

提前致谢！

Answer 1

我知道你说设置 layer.shadowOffset 对你不起作用，但你可以输入负值，所以设置它 layer.shadowOffset = CGSizeMake(0.0, -2.0) 会接近你正在寻找的效果，但我当然希望你希望它在三个方面是均匀的。

所以我们在这里使用layer.shadowPath！

UIView *block1 = [[UIView alloc] initWithFrame:CGRectMake(32.0, 32.0, 128.0, 128.0)];
[block1 setBackgroundColor:[UIColor orangeColor]];
[self.view addSubview:block1];

block1.layer.masksToBounds = NO;
block1.layer.shadowOffset = CGSizeMake(0, 0);
block1.layer.shadowRadius = 1;
block1.layer.shadowOpacity = 0.7;

UIBezierPath *path = [UIBezierPath bezierPath];

// Start at the Top Left Corner
[path moveToPoint:CGPointMake(0.0, 0.0)];

// Move to the Top Right Corner
[path addLineToPoint:CGPointMake(CGRectGetWidth(block1.frame), 0.0)];

// Move to the Bottom Right Corner
[path addLineToPoint:CGPointMake(CGRectGetWidth(block1.frame), CGRectGetHeight(block1.frame))];

// This is the extra point in the middle :) Its the secret sauce.
[path addLineToPoint:CGPointMake(CGRectGetWidth(block1.frame) / 2.0, CGRectGetHeight(block1.frame) / 2.0)];

// Move to the Bottom Left Corner
[path addLineToPoint:CGPointMake(0.0, CGRectGetHeight(block1.frame))];

// Move to the Close the Path
[path closePath];

block1.layer.shadowPath = path.CGPath;

为了让您了解发生了什么，这是您刚刚绘制的实际阴影路径:)

可以将多余的中间点移动到其他行之前或之后，以选择省略哪一侧。

Answer 2

更新 Ryan Poolos 对 Swift 3.0 的回答

感谢 Ryan Poolos

class sampleViewController: UIViewController {
    var block1: UIView! = nil

    override func viewDidLoad() {

        super.viewDidLoad()
        block1 = UIView(frame: CGRect(x: 32.0, y: 32.0, width: 128.0, height: 128.0))
        block1.backgroundColor = UIColor.orange
        self.view.addSubview(block1)

        block1.layer.masksToBounds = false
        block1.layer.shadowOffset = CGSize(width: 0.0, height: 0.0)
        block1.layer.shadowRadius = 1.0
        block1.layer.shadowOpacity = 0.7

        let path = UIBezierPath()

        // Start at the Top Left Corner
        path.move(to: CGPoint(x: 0.0, y: 0.0))

        // Move to the Top Right Corner
        path.addLine(to: CGPoint(x: block1.frame.size.width, y: 0.0))

        // Move to the Bottom Right Corner
        path.addLine(to: CGPoint(x: block1.frame.size.width, y: block1.frame.size.height))

        // This is the extra point in the middle :) Its the secret sauce.
        path.addLine(to: CGPoint(x: block1.frame.size.width/2.0, y: block1.frame.size.height/2.0))

        // Move to the Bottom Left Corner
        path.addLine(to: CGPoint(x: 0.0, y: block1.frame.size.height))

        path.close()

        block1.layer.shadowPath = path.cgPath
    }
}

结果：

Answer 3

感谢Ashok R 的快速代码，对其他答案有所改进。

由于我们在视图的背景中创建了一个三角形视图，所有边都有阴影，因此不需要在边上添加一个白色三角形阴影。

如果视图的宽度相对大于高度，它会中断。

解决方法是将不需要阴影的线的路径稍微移向视图的那一侧，而不是完全创建三角形视图路径。

我为此创建了一个扩展 -

extension UIView {
    func addshadow(top: Bool,
                   left: Bool,
                   bottom: Bool,
                   right: Bool,
                   shadowRadius: CGFloat = 2.0) {

        self.layer.masksToBounds = false
        self.layer.shadowOffset = CGSize(width: 0.0, height: 0.0)
        self.layer.shadowRadius = shadowRadius
        self.layer.shadowOpacity = 1.0

        let path = UIBezierPath()
        var x: CGFloat = 0
        var y: CGFloat = 0
        var viewWidth = self.frame.width
        var viewHeight = self.frame.height

        // here x, y, viewWidth, and viewHeight can be changed in
        // order to play around with the shadow paths.
        if (!top) {
            y+=(shadowRadius+1)
        }
        if (!bottom) {
            viewHeight-=(shadowRadius+1)
        }
        if (!left) {
            x+=(shadowRadius+1)
        }
        if (!right) {
            viewWidth-=(shadowRadius+1)
        }
        // selecting top most point
        path.move(to: CGPoint(x: x, y: y))
        // Move to the Bottom Left Corner, this will cover left edges
        /*
         |☐
         */
        path.addLine(to: CGPoint(x: x, y: viewHeight))
        // Move to the Bottom Right Corner, this will cover bottom edge
        /*
         ☐
         -
         */
        path.addLine(to: CGPoint(x: viewWidth, y: viewHeight))
        // Move to the Top Right Corner, this will cover right edge
        /*
         ☐|
         */
        path.addLine(to: CGPoint(x: viewWidth, y: y))
        // Move back to the initial point, this will cover the top edge
        /*
         _
         ☐
         */        
        path.close()
        self.layer.shadowPath = path.cgPath
    }

并为您希望阴影出现的任何一侧设置布尔值 true

myView.addshadow(top: false, left: true, bottom: true, right: true, shadowRadius: 2.0)

//阴影半径在上面是可选的，默认设置为2.0

或 myView.addshadow(top: true, left: true, bottom: true, right: true, shadowRadius: 2.0)

或 myView.addshadow(top: false, left: false, bottom: true, right: true, shadowRadius: 2.0)

Answer 4

试试这个

extension CALayer {
func applySketchShadow(color: UIColor, alpha: CGFloat, x: CGFloat, y: CGFloat, blur: CGFloat, spread: CGFloat)
{
    shadowColor = color.cgColor
    shadowOpacity = alpha
    shadowOffset = CGSize(width: x, height: y)
    shadowRadius = blur / 2.0
    if spread == 0 {
        shadowPath = nil
    } else {
        let dx = -spread
        let rect = bounds.insetBy(dx: dx, dy: dx)
        shadowPath = UIBezierPath(rect: rect).cgPath
    }
}