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

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

其他回答

对于那些没能让这个工作的人(就像我自己一样!),在尝试了所有的答案后,只要确保剪辑子视图没有在属性检查器中启用…

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];

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;

答得很好,但我想再补充一点

如果你遇到一个问题,当你有表格单元格,Deque一个新单元格有一个不匹配的阴影,所以在这种情况下,你需要把你的阴影代码在一个layoutSubviews方法,这样它将在所有条件下表现良好。

-(void)layoutSubviews{
    [super layoutSubviews];

    [self.contentView setNeedsLayout];
    [self.contentView layoutIfNeeded];
    [VPShadow applyShadowView:self];
}

或者在ViewControllers中为特定的视图放置阴影代码在下面的方法中,这样它就能很好地工作

-(void)viewDidLayoutSubviews{
    [super viewDidLayoutSubviews];

    [self.viewShadow layoutIfNeeded];
    [VPShadow applyShadowView:self.viewShadow];
}

我已经修改了我的影子实现为新的开发更普遍的形式,例如:

/*!
 @brief Add shadow to a view.

 @param layer CALayer of the view.

 */
+(void)applyShadowOnView:(CALayer *)layer OffsetX:(CGFloat)x OffsetY:(CGFloat)y blur:(CGFloat)radius opacity:(CGFloat)alpha RoundingCorners:(CGFloat)cornerRadius{
    UIBezierPath *shadowPath = [UIBezierPath bezierPathWithRoundedRect:layer.bounds cornerRadius:cornerRadius];
    layer.masksToBounds = NO;
    layer.shadowColor = [UIColor blackColor].CGColor;
    layer.shadowOffset = CGSizeMake(x,y);// shadow x and y
    layer.shadowOpacity = alpha;
    layer.shadowRadius = radius;// blur effect
    layer.shadowPath = shadowPath.CGPath;
}

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