我如何在UIView下画一个阴影?

我试图在Cocoa Touch的UIView的底部边缘下画一个阴影。我知道我应该使用CGContextSetShadow()来绘制阴影，但Quartz 2D编程指南有点模糊:

保存图形状态。调用CGContextSetShadow函数，传递适当的值。执行要应用阴影的所有绘图。恢复图形状态

我已经尝试了以下在一个UIView子类:

- (void)drawRect:(CGRect)rect {
    CGContextRef currentContext = UIGraphicsGetCurrentContext();
    CGContextSaveGState(currentContext);
    CGContextSetShadow(currentContext, CGSizeMake(-15, 20), 5);
    CGContextRestoreGState(currentContext);
    [super drawRect: rect];
}

．．但是这对我来说不工作，我有点卡住了(a)下一步要去哪里(b)如果我需要对我的UIView做什么来让这个工作?

当前回答

斯威夫特3

extension UIView {
    func installShadow() {
        layer.cornerRadius = 2
        layer.masksToBounds = false
        layer.shadowColor = UIColor.black.cgColor
        layer.shadowOffset = CGSize(width: 0, height: 1)
        layer.shadowOpacity = 0.45
        layer.shadowPath = UIBezierPath(rect: bounds).cgPath
        layer.shadowRadius = 1.0
    }
}

2016-12-14 23:15:14

其他回答

斯威夫特3

self.paddingView.layer.masksToBounds = false
self.paddingView.layer.shadowOffset = CGSize(width: -15, height: 10)
self.paddingView.layer.shadowRadius = 5
self.paddingView.layer.shadowOpacity = 0.5

2017-08-11 17:38:28

斯威夫特3

extension UIView {
    func installShadow() {
        layer.cornerRadius = 2
        layer.masksToBounds = false
        layer.shadowColor = UIColor.black.cgColor
        layer.shadowOffset = CGSize(width: 0, height: 1)
        layer.shadowOpacity = 0.45
        layer.shadowPath = UIBezierPath(rect: bounds).cgPath
        layer.shadowRadius = 1.0
    }
}

2016-12-14 23:15:14

在Swift 4中使用IBDesignable和IBInspectable绘制阴影

如何使用

Sketch和xcode并排

代码

@IBDesignable class ShadowView: UIView {

    @IBInspectable var shadowColor: UIColor? {
        get {
            if let color = layer.shadowColor {
                return UIColor(cgColor: color)
            }
            return nil
        }
        set {
            if let color = newValue {
                layer.shadowColor = color.cgColor
            } else {
                layer.shadowColor = nil
            }
        }
    }

    @IBInspectable var shadowOpacity: Float {
        get {
            return layer.shadowOpacity
        }
        set {
            layer.shadowOpacity = newValue
        }
    }

    @IBInspectable var shadowOffset: CGPoint {
        get {
            return CGPoint(x: layer.shadowOffset.width, y:layer.shadowOffset.height)
        }
        set {
            layer.shadowOffset = CGSize(width: newValue.x, height: newValue.y)
        }

     }

    @IBInspectable var shadowBlur: CGFloat {
        get {
            return layer.shadowRadius
        }
        set {
            layer.shadowRadius = newValue / 2.0
        }
    }

    @IBInspectable var shadowSpread: CGFloat = 0 {
        didSet {
            if shadowSpread == 0 {
                layer.shadowPath = nil
            } else {
                let dx = -shadowSpread
                let rect = bounds.insetBy(dx: dx, dy: dx)
                layer.shadowPath = UIBezierPath(rect: rect).cgPath
            }
        }
    }
}

输出

2019-11-11 15:58:21

你可以使用我为阴影和角半径创建的效用函数，如下所示:

- (void)addShadowWithRadius:(CGFloat)shadowRadius withShadowOpacity:(CGFloat)shadowOpacity withShadowOffset:(CGSize)shadowOffset withShadowColor:(UIColor *)shadowColor withCornerRadius:(CGFloat)cornerRadius withBorderColor:(UIColor *)borderColor withBorderWidth:(CGFloat)borderWidth forView:(UIView *)view{

    // drop shadow
    [view.layer setShadowRadius:shadowRadius];
    [view.layer setShadowOpacity:shadowOpacity];
    [view.layer setShadowOffset:shadowOffset];
    [view.layer setShadowColor:shadowColor.CGColor];

    // border radius
    [view.layer setCornerRadius:cornerRadius];

    // border
    [view.layer setBorderColor:borderColor.CGColor];
    [view.layer setBorderWidth:borderWidth];
}

希望对你有所帮助!!

2017-09-13 11:09:53

我把它作为我效用的一部分。有了这个，我们不仅可以设置阴影，还可以为任何UIView获得圆角。你也可以设置你喜欢什么颜色的阴影。通常情况下，黑色是首选，但有时，当背景是非白色时，你可能想要其他颜色。这是我用的-

in utils.m
+ (void)roundedLayer:(CALayer *)viewLayer 
              radius:(float)r 
              shadow:(BOOL)s
{
    [viewLayer setMasksToBounds:YES];
    [viewLayer setCornerRadius:r];        
    [viewLayer setBorderColor:[RGB(180, 180, 180) CGColor]];
    [viewLayer setBorderWidth:1.0f];
    if(s)
    {
        [viewLayer setShadowColor:[RGB(0, 0, 0) CGColor]];
        [viewLayer setShadowOffset:CGSizeMake(0, 0)];
        [viewLayer setShadowOpacity:1];
        [viewLayer setShadowRadius:2.0];
    }
    return;
}

要使用这个，我们需要调用它- [utils roundedLayer:yourview。图层半径:5.0f阴影:YES];

2011-10-24 06:00:24

我如何在UIView下画一个阴影?

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