[英]How do I draw a shadow under a UIView?
我正在尝试在 Cocoa Touch 中的UIView
的底部边缘下绘制阴影。 我知道我应该使用CGContextSetShadow()
来绘制阴影,但是 Quartz 2D 编程指南有点模糊:
CGContextSetShadow
,传递适当的值。我在UIView
子类中尝试了以下内容:
- (void)drawRect:(CGRect)rect {
CGContextRef currentContext = UIGraphicsGetCurrentContext();
CGContextSaveGState(currentContext);
CGContextSetShadow(currentContext, CGSizeMake(-15, 20), 5);
CGContextRestoreGState(currentContext);
[super drawRect: rect];
}
..但这对我不起作用,我对 (a) 下一步要去哪里以及 (b) 是否需要对UIView
做任何事情才能使这项工作发挥作用?
一个更简单的方法是在初始化时设置视图的一些层属性:
self.layer.masksToBounds = NO;
self.layer.shadowOffset = CGSizeMake(-15, 20);
self.layer.shadowRadius = 5;
self.layer.shadowOpacity = 0.5;
您需要导入 QuartzCore。
#import <QuartzCore/QuartzCore.h>
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;
这会减慢应用程序的速度。 只要您的视图是可见的矩形,添加以下行可以提高性能:
self.layer.shadowPath = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;
相同的解决方案,但只是提醒您:您可以直接在故事板中定义阴影。
前任:
在您当前的代码中,您保存当前上下文的GState
,将其配置为绘制阴影 .. 并将其恢复到配置为绘制阴影之前的状态。 然后,最后,您调用超类的drawRect
: 实现。
任何应该受阴影设置影响的绘图都需要
CGContextSetShadow(currentContext, CGSizeMake(-15, 20), 5);
但
CGContextRestoreGState(currentContext);
因此,如果您希望超类的drawRect:
被“包裹”在阴影中,那么如果您像这样重新排列代码呢?
- (void)drawRect:(CGRect)rect {
CGContextRef currentContext = UIGraphicsGetCurrentContext();
CGContextSaveGState(currentContext);
CGContextSetShadow(currentContext, CGSizeMake(-15, 20), 5);
[super drawRect: rect];
CGContextRestoreGState(currentContext);
}
你可以试试这个....你可以玩这些值。 shadowRadius
决定了模糊量。 shadowOffset
决定了阴影的shadowOffset
。
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
传播示例
创建基本阴影
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 中的基本阴影示例
使用 Interface Builder 的简单干净的解决方案
在您的项目中添加一个名为 UIView.swift 的文件(或将其粘贴到任何文件中):
import UIKit
@IBDesignable extension UIView {
/* The color of the shadow. Defaults to opaque black. Colors created
* from patterns are currently NOT supported. Animatable. */
@IBInspectable var shadowColor: UIColor? {
set {
layer.shadowColor = newValue!.CGColor
}
get {
if let color = layer.shadowColor {
return UIColor(CGColor:color)
}
else {
return nil
}
}
}
/* The opacity of the shadow. Defaults to 0. Specifying a value outside the
* [0,1] range will give undefined results. Animatable. */
@IBInspectable var shadowOpacity: Float {
set {
layer.shadowOpacity = newValue
}
get {
return layer.shadowOpacity
}
}
/* The shadow offset. Defaults to (0, -3). Animatable. */
@IBInspectable var shadowOffset: CGPoint {
set {
layer.shadowOffset = CGSize(width: newValue.x, height: newValue.y)
}
get {
return CGPoint(x: layer.shadowOffset.width, y:layer.shadowOffset.height)
}
}
/* The blur radius used to create the shadow. Defaults to 3. Animatable. */
@IBInspectable var shadowRadius: CGFloat {
set {
layer.shadowRadius = newValue
}
get {
return layer.shadowRadius
}
}
}
然后这将在 Interface Builder 中为 Utilities Panel > Attributes Inspector 中的每个视图提供:
您现在可以轻松设置阴影。
笔记:
- 阴影不会出现在 IB 中,只会在运行时出现。
- 正如 Mazen Kasser 所说
对于那些未能使其工作的人 [...] 确保未启用 Clip Subviews (
clipsToBounds
)
我使用它作为我的实用程序的一部分。 有了这个,我们不仅可以设置阴影,还可以为任何UIView
设置圆角。 您也可以设置您喜欢的颜色阴影。 通常首选黑色,但有时,当背景为非白色时,您可能需要其他颜色。 这是我使用的 -
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;
}
要使用它,我们需要调用它 - [utils roundedLayer:yourview.layer radius:5.0f shadow:YES];
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
}
}
如果您想使用 StoryBoard 并且不想继续输入运行时属性,您可以轻松创建视图的扩展并使它们在故事板中可用。
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
}
}
}
对于在尝试了所有答案后未能使其正常工作的人(作为我自己!),只需确保在属性检查器中未启用剪辑子视图...
在 Swift 4 中使用 IBDesignable 和 IBInspectable 绘制阴影
如何使用它
草图和 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
您可以使用我为阴影和角半径创建的实用函数,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];
}
希望能帮到你!!!
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
一切都很好,但我想再补充一点
如果您在拥有表格单元格时遇到问题,Deque 一个新单元格会导致 shadow 不匹配,因此在这种情况下,您需要将 shadow 代码放置在 layoutSubviews 方法中,以便它在所有条件下都能正常运行。
-(void)layoutSubviews{
[super layoutSubviews];
[self.contentView setNeedsLayout];
[self.contentView layoutIfNeeded];
[VPShadow applyShadowView:self];
}
或在特定视图的 ViewControllers 中,将阴影代码放置在以下方法中,使其运行良好
-(void)viewDidLayoutSubviews{
[super viewDidLayoutSubviews];
[self.viewShadow layoutIfNeeded];
[VPShadow applyShadowView:self.viewShadow];
}
我已经为新开发人员修改了我的影子实现,以获得更通用的形式,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;
}
对于 Xamarians 同行,答案的 Xamarin.iOS/C# 版本如下所示:
public override void DrawRect(CGRect area, UIViewPrintFormatter formatter)
{
CGContext currentContext = UIGraphics.GetCurrentContext();
currentContext.SaveState();
currentContext.SetShadow(new CGSize(-15, 20), 5);
base.DrawRect(area, formatter);
currentContext.RestoreState();
}
主要区别在于您获得了一个CGContext
实例,您可以在该实例上直接调用适当的方法。
您可以使用此Extension
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
}
}
你可以这样称呼它
your_Custom_View.addShadow(offset: CGSize(width: 0, height: 1), color: UIColor.black, radius: 2.0, opacity: 1.0)
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