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

self.layer.masksToBounds = NO;
self.layer.cornerRadius = 8; // if you like rounded corners
self.layer.shadowOffset = CGSizeMake(-15, 20);
self.layer.shadowRadius = 5;
self.layer.shadowOpacity = 0.5;

这将降低应用程序的速度。添加下面的行可以提高性能，只要你的视图是可见的矩形:

self.layer.shadowPath = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;

2011-03-25 03:03:38

其他回答

如果你想使用StoryBoard并且不想一直输入运行时属性，你可以很容易地为视图创建一个扩展，并使它们在StoryBoard中可用。

步骤1。创建扩展

extension UIView {

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

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

@IBInspectable var shadowOffset: CGSize {
    get {
        return layer.shadowOffset
    }
    set {
        layer.shadowOffset = newValue
    }
}

@IBInspectable var maskToBound: Bool {
    get {
        return layer.masksToBounds
    }
    set {
        layer.masksToBounds = newValue
    }
}
}

步骤2。您现在可以在故事板中使用这些属性

2018-08-22 08:17:15

self.layer.masksToBounds = NO;
self.layer.cornerRadius = 8; // if you like rounded corners
self.layer.shadowOffset = CGSizeMake(-15, 20);
self.layer.shadowRadius = 5;
self.layer.shadowOpacity = 0.5;

这将降低应用程序的速度。添加下面的行可以提高性能，只要你的视图是可见的矩形:

self.layer.shadowPath = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;

2011-03-25 03:03:38

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

你可以使用这个扩展来添加阴影

extension UIView {

    func addShadow(offset: CGSize, color: UIColor, radius: CGFloat, opacity: Float)
    {
        layer.masksToBounds = false
        layer.shadowOffset = offset
        layer.shadowColor = color.cgColor
        layer.shadowRadius = radius
        layer.shadowOpacity = opacity

        let backgroundCGColor = backgroundColor?.cgColor
        backgroundColor = nil
        layer.backgroundColor =  backgroundCGColor
    }
}

你可以称之为

your_Custom_View.addShadow(offset: CGSize(width: 0, height: 1), color: UIColor.black, radius: 2.0, opacity: 1.0)

2019-10-13 10:45:44

你可以试试这个....你可以调整数值。阴影半径决定了模糊的数量。shadowOffset指定阴影的位置。

斯威夫特2.0

let radius: CGFloat = demoView.frame.width / 2.0 //change it to .height if you need spread for height
let shadowPath = UIBezierPath(rect: CGRect(x: 0, y: 0, width: 2.1 * radius, height: demoView.frame.height))
//Change 2.1 to amount of spread you need and for height replace the code for height

demoView.layer.cornerRadius = 2
demoView.layer.shadowColor = UIColor.blackColor().CGColor
demoView.layer.shadowOffset = CGSize(width: 0.5, height: 0.4)  //Here you control x and y
demoView.layer.shadowOpacity = 0.5
demoView.layer.shadowRadius = 5.0 //Here your control your blur
demoView.layer.masksToBounds =  false
demoView.layer.shadowPath = shadowPath.CGPath

斯威夫特3.0

let radius: CGFloat = demoView.frame.width / 2.0 //change it to .height if you need spread for height 
let shadowPath = UIBezierPath(rect: CGRect(x: 0, y: 0, width: 2.1 * radius, height: demoView.frame.height)) 
//Change 2.1 to amount of spread you need and for height replace the code for height

demoView.layer.cornerRadius = 2
demoView.layer.shadowColor = UIColor.black.cgColor
demoView.layer.shadowOffset = CGSize(width: 0.5, height: 0.4)  //Here you control x and y
demoView.layer.shadowOpacity = 0.5
demoView.layer.shadowRadius = 5.0 //Here your control your blur
demoView.layer.masksToBounds =  false
demoView.layer.shadowPath = shadowPath.cgPath

关于传播的例子

创建一个基本的阴影

    demoView.layer.cornerRadius = 2
    demoView.layer.shadowColor = UIColor.blackColor().CGColor
    demoView.layer.shadowOffset = CGSizeMake(0.5, 4.0); //Here your control your spread
    demoView.layer.shadowOpacity = 0.5 
    demoView.layer.shadowRadius = 5.0 //Here your control your blur

Swift 2.0中的基本Shadow示例

2016-10-20 08:24:59

我如何在UIView下画一个阴影?

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