如何在UIView下绘制阴影?
-
03-07-2019 - |
题
我正试图在Cocoa Touch的 UIView
的底边画一个阴影。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:
- 保存图形状态。
- 调用函数
CGContextSetShadow
,传递适当的值。 - 执行要应用阴影的所有绘图。
- 恢复图形状态 醇>
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,我有点不知道(a)下一步去哪里和(b)如果我需要对 UIView
做任何事情让这个工作?
解决方案
在当前代码中,保存当前上下文的 GState
,将其配置为绘制阴影..并将其恢复为将其配置为绘制阴影之前的状态。然后,最后,您调用超类的 drawRect
的实现:。
任何应受阴影设置影响的绘图都需要在
之后发生CGContextSetShadow(currentContext, CGSizeMake(-15, 20), 5);
但之前
CGContextRestoreGState(currentContext);
因此,如果您希望超类的 drawRect:
被包裹在阴影中,那么如果您重新排列代码会怎么样?
- (void)drawRect:(CGRect)rect {
CGContextRef currentContext = UIGraphicsGetCurrentContext();
CGContextSaveGState(currentContext);
CGContextSetShadow(currentContext, CGSizeMake(-15, 20), 5);
[super drawRect: rect];
CGContextRestoreGState(currentContext);
}
其他提示
更简单的方法是在初始化时设置视图的某些图层属性:
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;
这会降低应用程序的速度。 只要您的视图明显是矩形,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。
例如:
你可以尝试这个......你可以玩这些值。
shadowRadius
决定了模糊量。 shadowOffset
指示阴影的去向。
Swift 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
Swift 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
的简单清洁解决方案在项目中添加名为UIView.swift的文件(或者只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中的每个视图提供&gt;属性检查器:
您现在可以轻松设置阴影。
注意:结果
- 只有在运行时,阴影才会出现在IB中。
- 正如Mazen Kasser所说
对于未能使其工作的人[...]确保未启用剪辑子视图(
clipsToBounds
)
我将它用作我的工具的一部分。有了这个,我们不仅可以设置阴影,还可以为任何 UIView
获得一个圆角。您也可以设置您喜欢的颜色阴影。通常黑色是首选,但有时,当背景为非白色时,您可能需要其他东西。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];
Swift 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
}
}
如果您想使用StoryBoard并且不想继续输入运行时属性,您可以轻松地创建视图扩展并使其在故事板中可用。
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
}
}
}
对于那些在尝试所有答案后未能使其工作的人(正如我自己!),只需确保在属性检查器中未启用剪辑子视图 ...
Swift 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
您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];
}
希望它能帮到你!!!
所有答案都很好,但我想再增加一点
如果在有表格单元格时遇到问题,则Deque新单元格中的阴影不匹配,因此在这种情况下,您需要将影子代码放在layoutSubviews方法中,以便它在所有条件下都能很好地运行。
-(void)layoutSubviews{
[super layoutSubviews];
[self.contentView setNeedsLayout];
[self.contentView layoutIfNeeded];
[VPShadow applyShadowView:self];
}
或在ViewControllers中为特定视图放置以下方法中的阴影代码,以便它可以正常工作
-(void)viewDidLayoutSubviews{
[super viewDidLayoutSubviews];
[self.viewShadow layoutIfNeeded];
[VPShadow applyShadowView:self.viewShadow];
}
我为新的开发者修改了我的阴影实现,以获得更通用的形式:
/*!
@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同事,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 CGContext
的实例,您可以在其上直接调用相应的方法。