UIView 層上的內陰影效果？

Question

我有以下 CALayer：

CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = CGRectMake(8, 57, 296, 30);
gradient.cornerRadius = 3.0f;
gradient.colors = [NSArray arrayWithObjects:(id)[RGB(130, 0, 140) CGColor], (id)[RGB(108, 0, 120) CGColor], nil];
[self.layer insertSublayer:gradient atIndex:0];

我想為其添加內部陰影效果，但我不太確定如何執行此操作。 我想我需要在 drawRect 中繪制，但是這會在其他 UIView 對象的頂部添加圖層，因為它應該是一些按鈕后面的一個欄，所以我不知道該怎么做？

我可以添加另一層，但同樣，不確定如何實現內部陰影效果（如下所示：

幫助贊賞...

Answer 1

對於想知道如何按照 Costique 的建議使用 Core Graphics 繪制內部陰影的其他人，方法如下：（在 iOS 上根據需要進行調整）

在您的 drawRect: 方法中...

CGRect bounds = [self bounds];
CGContextRef context = UIGraphicsGetCurrentContext();
CGFloat radius = 0.5f * CGRectGetHeight(bounds);


// Create the "visible" path, which will be the shape that gets the inner shadow
// In this case it's just a rounded rect, but could be as complex as your want
CGMutablePathRef visiblePath = CGPathCreateMutable();
CGRect innerRect = CGRectInset(bounds, radius, radius);
CGPathMoveToPoint(visiblePath, NULL, innerRect.origin.x, bounds.origin.y);
CGPathAddLineToPoint(visiblePath, NULL, innerRect.origin.x + innerRect.size.width, bounds.origin.y);
CGPathAddArcToPoint(visiblePath, NULL, bounds.origin.x + bounds.size.width, bounds.origin.y, bounds.origin.x + bounds.size.width, innerRect.origin.y, radius);
CGPathAddLineToPoint(visiblePath, NULL, bounds.origin.x + bounds.size.width, innerRect.origin.y + innerRect.size.height);
CGPathAddArcToPoint(visiblePath, NULL,  bounds.origin.x + bounds.size.width, bounds.origin.y + bounds.size.height, innerRect.origin.x + innerRect.size.width, bounds.origin.y + bounds.size.height, radius);
CGPathAddLineToPoint(visiblePath, NULL, innerRect.origin.x, bounds.origin.y + bounds.size.height);
CGPathAddArcToPoint(visiblePath, NULL,  bounds.origin.x, bounds.origin.y + bounds.size.height, bounds.origin.x, innerRect.origin.y + innerRect.size.height, radius);
CGPathAddLineToPoint(visiblePath, NULL, bounds.origin.x, innerRect.origin.y);
CGPathAddArcToPoint(visiblePath, NULL,  bounds.origin.x, bounds.origin.y, innerRect.origin.x, bounds.origin.y, radius);
CGPathCloseSubpath(visiblePath);

// Fill this path
UIColor *aColor = [UIColor redColor];
[aColor setFill];
CGContextAddPath(context, visiblePath);
CGContextFillPath(context);


// Now create a larger rectangle, which we're going to subtract the visible path from
// and apply a shadow
CGMutablePathRef path = CGPathCreateMutable();
//(when drawing the shadow for a path whichs bounding box is not known pass "CGPathGetPathBoundingBox(visiblePath)" instead of "bounds" in the following line:)
//-42 cuould just be any offset > 0
CGPathAddRect(path, NULL, CGRectInset(bounds, -42, -42));
    
// Add the visible path (so that it gets subtracted for the shadow)
CGPathAddPath(path, NULL, visiblePath);
CGPathCloseSubpath(path);

// Add the visible paths as the clipping path to the context
CGContextAddPath(context, visiblePath); 
CGContextClip(context);         


// Now setup the shadow properties on the context
aColor = [UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:0.5f];
CGContextSaveGState(context);
CGContextSetShadowWithColor(context, CGSizeMake(0.0f, 1.0f), 3.0f, [aColor CGColor]);   

// Now fill the rectangle, so the shadow gets drawn
[aColor setFill];   
CGContextSaveGState(context);   
CGContextAddPath(context, path);
CGContextEOFillPath(context);

// Release the paths
CGPathRelease(path);    
CGPathRelease(visiblePath);

所以，基本上有以下步驟：

1. 創建你的路徑
2. 設置你想要的填充顏色，將此路徑添加到上下文中，並填充上下文
3. 現在創建一個更大的矩形來限制可見路徑。 在關閉此路徑之前，添加可見路徑。 然后關閉路徑，以便創建一個從中減去可見路徑的形狀。 您可能想要研究填充方法（偶數/奇數的非零纏繞），具體取決於您創建這些路徑的方式。 從本質上講，要在將它們加在一起時使子路徑“相減”，您需要以相反的方向繪制（或構建它們），一個順時針，另一個逆時針。
4. 然后你需要將你的可見路徑設置為上下文的剪切路徑，這樣你就不會在它之外繪制任何東西到屏幕上。
5. 然后在上下文中設置陰影，包括偏移、模糊和顏色。
6. 然后用其中的孔填充大形狀。 顏色無關緊要，因為如果您做的一切都正確，您將看不到這種顏色，只會看到陰影。

Answer 2

我知道我參加這個聚會遲到了，但這會幫助我在旅行中盡早找到......

為了在信用到期的地方給予信用，這本質上是對 Daniel Thorpe 對 Costique 解決方案的詳細闡述的修改，該解決方案是從更大的區域中減去一個較小的區域。 此版本適用於使用圖層組合而不是覆蓋-drawRect:

CAShapeLayer類可用於實現相同的效果：

CAShapeLayer *shadowLayer = [CAShapeLayer layer];
[shadowLayer setFrame:[self bounds]];

// Standard shadow stuff
[shadowLayer setShadowColor:[[UIColor colorWithWhite:0 alpha:1] CGColor]];
[shadowLayer setShadowOffset:CGSizeMake(0.0f, 0.0f)];
[shadowLayer setShadowOpacity:1.0f];
[shadowLayer setShadowRadius:5];

// Causes the inner region in this example to NOT be filled.
[shadowLayer setFillRule:kCAFillRuleEvenOdd];

// Create the larger rectangle path.
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, CGRectInset(bounds, -42, -42));

// Add the inner path so it's subtracted from the outer path.
// someInnerPath could be a simple bounds rect, or maybe
// a rounded one for some extra fanciness.
CGPathAddPath(path, NULL, someInnerPath);
CGPathCloseSubpath(path);

[shadowLayer setPath:path];
CGPathRelease(path);

[[self layer] addSublayer:shadowLayer];

此時，如果您的父圖層未對其邊界進行遮罩，您將在圖層邊緣周圍看到遮罩層的額外區域。 如果您直接復制示例，這將是 42 像素的黑色。 要擺脫它，您可以簡單地使用另一個具有相同路徑的CAShapeLayer並將其設置為陰影層的蒙版：

CAShapeLayer *maskLayer = [CAShapeLayer layer];
[maskLayer setPath:someInnerPath];
[shadowLayer setMask:maskLayer];

我自己沒有對此進行基准測試，但我懷疑將這種方法與光柵化結合使用比覆蓋-drawRect:性能更高。

Answer 3

通過在邊界外制作一個大矩形路徑，減去一個邊界大小的矩形路徑並用“正常”陰影填充生成的路徑，可以使用 Core Graphics 繪制內部陰影。

但是，由於您需要將其與漸變圖層結合使用，我認為更簡單的解決方案是創建內部陰影的 9 部分透明 PNG 圖像並將其拉伸到合適的大小。 由 9 部分組成的陰影圖像如下所示（其大小為 21x21 像素）：

CALayer *innerShadowLayer = [CALayer layer];
innerShadowLayer.contents = (id)[UIImage imageNamed: @"innershadow.png"].CGImage;
innerShadowLayer.contentsCenter = CGRectMake(10.0f/21.0f, 10.0f/21.0f, 1.0f/21.0f, 1.0f/21.0f);

然后設置innerShadowLayer 的框架，它應該正確拉伸陰影。

Answer 4

在 Swift 中僅使用 CALayer 的簡化版本：

import UIKit

final class FrameView : UIView {
    init() {
        super.init(frame: CGRect.zero)
        backgroundColor = UIColor.white
    }

    @available(*, unavailable)
    required init?(coder decoder: NSCoder) { fatalError("unavailable") }

    override func layoutSubviews() {
        super.layoutSubviews()
        addInnerShadow()
    }

    private func addInnerShadow() {
        let innerShadow = CALayer()
        innerShadow.frame = bounds
        // Shadow path (1pt ring around bounds)
        let path = UIBezierPath(rect: innerShadow.bounds.insetBy(dx: -1, dy: -1))
        let cutout = UIBezierPath(rect: innerShadow.bounds).reversing()
        path.append(cutout)
        innerShadow.shadowPath = path.cgPath
        innerShadow.masksToBounds = true
        // Shadow properties
        innerShadow.shadowColor = UIColor(white: 0, alpha: 1).cgColor // UIColor(red: 0.71, green: 0.77, blue: 0.81, alpha: 1.0).cgColor
        innerShadow.shadowOffset = CGSize.zero
        innerShadow.shadowOpacity = 1
        innerShadow.shadowRadius = 3
        // Add
        layer.addSublayer(innerShadow)
    }
}

請注意，innerShadow 層不應具有不透明的背景顏色，因為這將呈現在陰影的前面。

Answer 5

有點迂回的方式，但它避免了必須使用圖像（閱讀：易於更改顏色、陰影半徑等）並且它只有幾行代碼。

1. 添加一個 UIImageView 作為您想要放置陰影的 UIView 的第一個子視圖。 我使用 IB，但您可以通過編程方式執行相同的操作。

2. 假設對 UIImageView 的引用是“innerShadow”

`

[[innerShadow layer] setMasksToBounds:YES];
[[innerShadow layer] setCornerRadius:12.0f];        
[[innerShadow layer] setBorderColor:[UIColorFromRGB(180, 180, 180) CGColor]];
[[innerShadow layer] setBorderWidth:1.0f];
[[innerShadow layer] setShadowColor:[UIColorFromRGB(0, 0, 0) CGColor]];
[[innerShadow layer] setShadowOffset:CGSizeMake(0, 0)];
[[innerShadow layer] setShadowOpacity:1];
[[innerShadow layer] setShadowRadius:2.0];

警告：你必須有一個邊框，否則陰影不會出現。 [UIColor clearColor] 不起作用。 在這個例子中，我使用了不同的顏色，但你可以弄亂它，讓它與陰影的開始顏色相同。 :)

請參閱下面關於UIColorFromRGB宏的UIColorFromRGB評論。

Answer 6

遲到總比不到好...

這是另一種方法，可能不會比已經發布的方法好，但它很好且簡單-

-(void)drawInnerShadowOnView:(UIView *)view
{
    UIImageView *innerShadowView = [[UIImageView alloc] initWithFrame:view.bounds];

    innerShadowView.contentMode = UIViewContentModeScaleToFill;
    innerShadowView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

    [view addSubview:innerShadowView];

    [innerShadowView.layer setMasksToBounds:YES];

    [innerShadowView.layer setBorderColor:[UIColor lightGrayColor].CGColor];
    [innerShadowView.layer setShadowColor:[UIColor blackColor].CGColor];
    [innerShadowView.layer setBorderWidth:1.0f];

    [innerShadowView.layer setShadowOffset:CGSizeMake(0, 0)];
    [innerShadowView.layer setShadowOpacity:1.0];

    // this is the inner shadow thickness
    [innerShadowView.layer setShadowRadius:1.5];
}

Answer 7

而不是通過 drawRect 繪制內部陰影或將 UIView 添加到視圖。 您可以直接將 CALayer 添加到邊框，例如：如果我想要 UIView V 底部的內陰影效果。

innerShadowOwnerLayer = [[CALayer alloc]init];
innerShadowOwnerLayer.frame = CGRectMake(0, V.frame.size.height+2, V.frame.size.width, 2);
innerShadowOwnerLayer.backgroundColor = [UIColor whiteColor].CGColor;

innerShadowOwnerLayer.shadowColor = [UIColor blackColor].CGColor;
innerShadowOwnerLayer.shadowOffset = CGSizeMake(0, 0);
innerShadowOwnerLayer.shadowRadius = 10.0;
innerShadowOwnerLayer.shadowOpacity = 0.7;

[V.layer addSubLayer:innerShadowOwnerLayer];

這為目標 UIView 添加了底部內陰影

Answer 8

這是 swift 的一個版本，更改startPoint和endPoint以使其在每一側。

        let layer = CAGradientLayer()
        layer.startPoint    = CGPointMake(0.5, 0.0);
        layer.endPoint      = CGPointMake(0.5, 1.0);
        layer.colors        = [UIColor(white: 0.1, alpha: 1.0).CGColor, UIColor(white: 0.1, alpha: 0.5).CGColor, UIColor.clearColor().CGColor]
        layer.locations     = [0.05, 0.2, 1.0 ]
        layer.frame         = CGRectMake(0, 0, self.view.frame.width, 60)
        self.view.layer.insertSublayer(layer, atIndex: 0)

Answer 9

這是您的解決方案，我已從PaintCode導出：

-(void) drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();

    //// Shadow Declarations
    UIColor* shadow = UIColor.whiteColor;
    CGSize shadowOffset = CGSizeMake(0, 0);
    CGFloat shadowBlurRadius = 10;

    //// Rectangle Drawing
    UIBezierPath* rectanglePath = [UIBezierPath bezierPathWithRect: self.bounds];
    [[UIColor blackColor] setFill];
    [rectanglePath fill];

    ////// Rectangle Inner Shadow
    CGContextSaveGState(context);
    UIRectClip(rectanglePath.bounds);
    CGContextSetShadowWithColor(context, CGSizeZero, 0, NULL);

    CGContextSetAlpha(context, CGColorGetAlpha([shadow CGColor]));
    CGContextBeginTransparencyLayer(context, NULL);
    {
        UIColor* opaqueShadow = [shadow colorWithAlphaComponent: 1];
        CGContextSetShadowWithColor(context, shadowOffset, shadowBlurRadius, [opaqueShadow CGColor]);
        CGContextSetBlendMode(context, kCGBlendModeSourceOut);
        CGContextBeginTransparencyLayer(context, NULL);

        [opaqueShadow setFill];
        [rectanglePath fill];

        CGContextEndTransparencyLayer(context);
    }
    CGContextEndTransparencyLayer(context);
    CGContextRestoreGState(context);
}

Answer 10

這是我在 Swift 4.2 中的解決方案。 你想試試嗎？

final class ACInnerShadowLayer : CAShapeLayer {

  var innerShadowColor: CGColor? = UIColor.black.cgColor {
    didSet { setNeedsDisplay() }
  }

  var innerShadowOffset: CGSize = .zero {
    didSet { setNeedsDisplay() }
  }

  var innerShadowRadius: CGFloat = 8 {
    didSet { setNeedsDisplay() }
  }

  var innerShadowOpacity: Float = 1 {
    didSet { setNeedsDisplay() }
  }

  override init() {
    super.init()

    masksToBounds = true
    contentsScale = UIScreen.main.scale

    setNeedsDisplay()
  }

  override init(layer: Any) {
      if let layer = layer as? InnerShadowLayer {
          innerShadowColor = layer.innerShadowColor
          innerShadowOffset = layer.innerShadowOffset
          innerShadowRadius = layer.innerShadowRadius
          innerShadowOpacity = layer.innerShadowOpacity
      }
      super.init(layer: layer)
  }

  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  override func draw(in ctx: CGContext) {
    ctx.setAllowsAntialiasing(true)
    ctx.setShouldAntialias(true)
    ctx.interpolationQuality = .high

    let colorspace = CGColorSpaceCreateDeviceRGB()

    var rect = bounds
    var radius = cornerRadius

    if borderWidth != 0 {
      rect = rect.insetBy(dx: borderWidth, dy: borderWidth)
      radius -= borderWidth
      radius = max(radius, 0)
    }

    let innerShadowPath = UIBezierPath(roundedRect: rect, cornerRadius: radius).cgPath
    ctx.addPath(innerShadowPath)
    ctx.clip()

    let shadowPath = CGMutablePath()
    let shadowRect = rect.insetBy(dx: -rect.size.width, dy: -rect.size.width)
    shadowPath.addRect(shadowRect)
    shadowPath.addPath(innerShadowPath)
    shadowPath.closeSubpath()

    if let innerShadowColor = innerShadowColor, let oldComponents = innerShadowColor.components {
      var newComponets = Array<CGFloat>(repeating: 0, count: 4) // [0, 0, 0, 0] as [CGFloat]
      let numberOfComponents = innerShadowColor.numberOfComponents

      switch numberOfComponents {
      case 2:
        newComponets[0] = oldComponents[0]
        newComponets[1] = oldComponents[0]
        newComponets[2] = oldComponents[0]
        newComponets[3] = oldComponents[1] * CGFloat(innerShadowOpacity)
      case 4:
        newComponets[0] = oldComponents[0]
        newComponets[1] = oldComponents[1]
        newComponets[2] = oldComponents[2]
        newComponets[3] = oldComponents[3] * CGFloat(innerShadowOpacity)
      default:
        break
      }

      if let innerShadowColorWithMultipliedAlpha = CGColor(colorSpace: colorspace, components: newComponets) {
        ctx.setFillColor(innerShadowColorWithMultipliedAlpha)
        ctx.setShadow(offset: innerShadowOffset, blur: innerShadowRadius, color: innerShadowColorWithMultipliedAlpha)
        ctx.addPath(shadowPath)
        ctx.fillPath(using: .evenOdd)
      }
    } 
  }
}

Answer 11

我參加聚會很晚了，但我想回饋社區。一個包含四個 UITextField 實例的 PIN 輸入屏幕，可以在 ViewController 中顯示一個原始字符或 (BOOL)[self isUsingBullets] 或 (BOOL)[self usingAsterisks]。 應用程序適用於 iPhone/iPhone 視網膜/iPad/iPad 視網膜，所以我不必提供四張圖像......

#import <QuartzCore/QuartzCore.h>

- (void)setTextFieldInnerGradient:(UITextField *)textField
{

    [textField setSecureTextEntry:self.isUsingBullets];
    [textField setBackgroundColor:[UIColor blackColor]];
    [textField setTextColor:[UIColor blackColor]];
    [textField setBorderStyle:UITextBorderStyleNone];
    [textField setClipsToBounds:YES];

    [textField.layer setBorderColor:[[UIColor blackColor] CGColor]];
    [textField.layer setBorderWidth:1.0f];

    // make a gradient off-white background
    CAGradientLayer *gradient = [CAGradientLayer layer];
    CGRect gradRect = CGRectInset([textField bounds], 3, 3);    // Reduce Width and Height and center layer
    gradRect.size.height += 2;  // minimise Bottom shadow, rely on clipping to remove these 2 pts.

    gradient.frame = gradRect;
    struct CGColor *topColor = [UIColor colorWithWhite:0.6f alpha:1.0f].CGColor;
    struct CGColor *bottomColor = [UIColor colorWithWhite:0.9f alpha:1.0f].CGColor;
    // We need to use this fancy __bridge object in order to get the array we want.
    gradient.colors = [NSArray arrayWithObjects:(__bridge id)topColor, (__bridge id)bottomColor, nil];
    [gradient setCornerRadius:4.0f];
    [gradient setShadowOffset:CGSizeMake(0, 0)];
    [gradient setShadowColor:[[UIColor whiteColor] CGColor]];
    [gradient setShadowOpacity:1.0f];
    [gradient setShadowRadius:3.0f];

    // Now we need to Blur the edges of this layer "so it blends"
    // This rasterizes the view down to 4x4 pixel chunks then scales it back up using bilinear filtering...
    // it's EXTREMELY fast and looks ok if you are just wanting to blur a background view under a modal view.
    // To undo it, just set the rasterization scale back to 1.0 or turn off rasterization.
    [gradient setRasterizationScale:0.25];
    [gradient setShouldRasterize:YES];

    [textField.layer insertSublayer:gradient atIndex:0];

    if (self.usingAsterisks) {
        [textField setFont:[UIFont systemFontOfSize:80.0]];
    } else {
        [textField setFont:[UIFont systemFontOfSize:40.0]];
    }
    [textField setTextAlignment:UITextAlignmentCenter];
    [textField setEnabled:NO];
}

我希望這可以幫助某人，因為這個論壇幫助了我。

Answer 12

查看Chris Emery撰寫的Quartz 中的Inner Shadows的精彩文章，其中解釋了PaintCode是如何繪制內部陰影的，並提供了一個干凈整潔的代碼片段：

- (void)drawInnerShadowInContext:(CGContextRef)context
                        withPath:(CGPathRef)path
                     shadowColor:(CGColorRef)shadowColor
                          offset:(CGSize)offset
                      blurRadius:(CGFloat)blurRadius 
{
    CGContextSaveGState(context);

    CGContextAddPath(context, path);
    CGContextClip(context);

    CGColorRef opaqueShadowColor = CGColorCreateCopyWithAlpha(shadowColor, 1.0);

    CGContextSetAlpha(context, CGColorGetAlpha(shadowColor));
    CGContextBeginTransparencyLayer(context, NULL);
        CGContextSetShadowWithColor(context, offset, blurRadius, opaqueShadowColor);
        CGContextSetBlendMode(context, kCGBlendModeSourceOut);
        CGContextSetFillColorWithColor(context, opaqueShadowColor);
        CGContextAddPath(context, path);
        CGContextFillPath(context);
    CGContextEndTransparencyLayer(context);

    CGContextRestoreGState(context);

    CGColorRelease(opaqueShadowColor);
}

Answer 13

在 Swift 中使用 CALayer 的可擴展解決方案

使用所描述的InnerShadowLayer您還可以僅為特定邊緣啟用內部陰影，不包括其他邊緣。 （例如，您只能在視圖的左側和頂部邊緣啟用內部陰影）

然后，您可以使用以下方法將InnerShadowLayer添加到您的視圖中：

init(...) {

    // ... your initialization code ...

    super.init(frame: .zero)
    layer.addSublayer(shadowLayer)
}

public override func layoutSubviews() {
    super.layoutSubviews()
    shadowLayer.frame = bounds
}

InnerShadowLayer實現

/// Shadow is a struct defining the different kinds of shadows
public struct Shadow {
    let x: CGFloat
    let y: CGFloat
    let blur: CGFloat
    let opacity: CGFloat
    let color: UIColor
}

/// A layer that applies an inner shadow to the specified edges of either its path or its bounds
public class InnerShadowLayer: CALayer {
    private let shadow: Shadow
    private let edge: UIRectEdge

    public init(shadow: Shadow, edge: UIRectEdge) {
        self.shadow = shadow
        self.edge = edge
        super.init()
        setupShadow()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    public override func layoutSublayers() {
        updateShadow()
    }

    private func setupShadow() {
        shadowColor = shadow.color.cgColor
        shadowOpacity = Float(shadow.opacity)
        shadowRadius = shadow.blur / 2.0
        masksToBounds = true
    }

    private func updateShadow() {
        shadowOffset = {
            let topWidth: CGFloat = 0
            let leftWidth = edge.contains(.left) ? shadow.y / 2 : 0
            let bottomWidth: CGFloat = 0
            let rightWidth = edge.contains(.right) ? -shadow.y / 2 : 0

            let topHeight = edge.contains(.top) ? shadow.y / 2 : 0
            let leftHeight: CGFloat = 0
            let bottomHeight = edge.contains(.bottom) ? -shadow.y / 2 : 0
            let rightHeight: CGFloat = 0

            return CGSize(width: [topWidth, leftWidth, bottomWidth, rightWidth].reduce(0, +),
                          height: [topHeight, leftHeight, bottomHeight, rightHeight].reduce(0, +))
        }()

        let insets = UIEdgeInsets(top: edge.contains(.top) ? -bounds.height : 0,
                                  left: edge.contains(.left) ? -bounds.width : 0,
                                  bottom: edge.contains(.bottom) ? -bounds.height : 0,
                                  right: edge.contains(.right) ? -bounds.width : 0)
        let path = UIBezierPath(rect: bounds.inset(by: insets))
        let cutout = UIBezierPath(rect: bounds).reversing()
        path.append(cutout)
        shadowPath = path.cgPath
    }
}

Answer 14

這段代碼對我有用

class InnerDropShadowView: UIView {
    override func draw(_ rect: CGRect) {
        //Drawing code
        let context = UIGraphicsGetCurrentContext()
        //// Shadow Declarations
        let shadow: UIColor? = UIColor.init(hexString: "a3a3a3", alpha: 1.0) //UIColor.black.withAlphaComponent(0.6) //UIColor.init(hexString: "d7d7da", alpha: 1.0)
        let shadowOffset = CGSize(width: 0, height: 0)
        let shadowBlurRadius: CGFloat = 7.5
        //// Rectangle Drawing
        let rectanglePath = UIBezierPath(rect: bounds)
        UIColor.groupTableViewBackground.setFill()
        rectanglePath.fill()
        ////// Rectangle Inner Shadow
        context?.saveGState()
        UIRectClip(rectanglePath.bounds)
        context?.setShadow(offset: CGSize.zero, blur: 0, color: nil)
        context?.setAlpha((shadow?.cgColor.alpha)!)
        context?.beginTransparencyLayer(auxiliaryInfo: nil)
        do {
            let opaqueShadow: UIColor? = shadow?.withAlphaComponent(1)
            context?.setShadow(offset: shadowOffset, blur: shadowBlurRadius, color: opaqueShadow?.cgColor)
            context!.setBlendMode(.sourceOut)
            context?.beginTransparencyLayer(auxiliaryInfo: nil)
            opaqueShadow?.setFill()
            rectanglePath.fill()
            context!.endTransparencyLayer()
        }
        context!.endTransparencyLayer()
        context?.restoreGState()
    }
}

Answer 15

有一些代碼在這里可以為你做這個。 如果您將視圖中的圖層（通過覆蓋+ (Class)layerClass ）更改為 JTAInnerShadowLayer，那么您可以在 init 方法中設置縮進圖層上的內部陰影，它會為您完成這項工作。 如果您還想繪制原始內容，請確保在縮進層上調用setDrawOriginalImage:yes 。 有一個關於如何工作的一個博客帖子在這里。

Answer 16

使用漸變層：

UIView * mapCover = [UIView new];
mapCover.frame = map.frame;
[view addSubview:mapCover];

CAGradientLayer * vertical = [CAGradientLayer layer];
vertical.frame = mapCover.bounds;
vertical.colors = [NSArray arrayWithObjects:(id)[UIColor whiteColor].CGColor,
                        (id)[[UIColor whiteColor] colorWithAlphaComponent:0.0f].CGColor,
                        (id)[[UIColor whiteColor] colorWithAlphaComponent:0.0f].CGColor,
                        (id)[UIColor whiteColor].CGColor, nil];
vertical.locations = @[@0.01,@0.1,@0.9,@0.99];
[mapCover.layer insertSublayer:vertical atIndex:0];

CAGradientLayer * horizontal = [CAGradientLayer layer];
horizontal.frame = mapCover.bounds;
horizontal.colors = [NSArray arrayWithObjects:(id)[UIColor whiteColor].CGColor,
                     (id)[[UIColor whiteColor] colorWithAlphaComponent:0.0f].CGColor,
                     (id)[[UIColor whiteColor] colorWithAlphaComponent:0.0f].CGColor,
                     (id)[UIColor whiteColor].CGColor, nil];
horizontal.locations = @[@0.01,@0.1,@0.9,@0.99];
horizontal.startPoint = CGPointMake(0.0, 0.5);
horizontal.endPoint = CGPointMake(1.0, 0.5);
[mapCover.layer insertSublayer:horizontal atIndex:0];

Answer 17

有一個簡單的解決方案 - 只需繪制正常陰影並旋轉，就像這樣

@objc func shadowView() -> UIView {
        let shadowView = UIView(frame: .zero)
        shadowView.backgroundColor = .white
        shadowView.layer.shadowColor = UIColor.grey.cgColor
        shadowView.layer.shadowOffset = CGSize(width: 0, height: 2)
        shadowView.layer.shadowOpacity = 1.0
        shadowView.layer.shadowRadius = 4
        shadowView.layer.compositingFilter = "multiplyBlendMode"
        return shadowView
    }

func idtm_addBottomShadow() {
        let shadow = shadowView()
        shadow.transform = transform.rotated(by: 180 * CGFloat(Double.pi))
        shadow.transform = transform.rotated(by: -1 * CGFloat(Double.pi))
        shadow.translatesAutoresizingMaskIntoConstraints = false
        addSubview(shadow)
        NSLayoutConstraint.activate([
            shadow.leadingAnchor.constraint(equalTo: leadingAnchor),
            shadow.trailingAnchor.constraint(equalTo: trailingAnchor),
            shadow.bottomAnchor.constraint(equalTo: bottomAnchor),
            shadow.heightAnchor.constraint(equalToConstant: 1),
            ])
    }