iphone ios layer 教程应用

CALayer(层)是屏幕上的一个矩形区域，在每一个UIView中都包含一个根CALayer，在UIView上的所有视觉效果都是在这个Layer上进行的。

CALayer外形特征主要包括：

1、层的大小尺寸

2、背景色

3、内容（可以填充图片或者使用Core Graphics绘制的内容）

4、矩形是否使用圆角

5、矩形是否有阴影

Layer有很多种，最常用也是最基本的是CALayer，当然还包括其他的子类：

CAScrollerLayer 简化显示层的一部分

CATextLayer 文本层

CAGradientLayer、CAShapeLayer等等

使用层之前，需要在项目中引入QuartzCore.framework框架

实例：

新建XCode项目LayerSample，导入QuartzCore.famework

在LayerSampleViewController.h文件中引入：

#import <QuartzCore/QuartzCore.h>
LayerSampleViewController.m文件，代码：
//
// LayerSampleViewController.m
// LayerSample
//
// Created by jordy on 11-3-28.
// Copyright 2011 vsp. All rights reserved.
//

#import "LayerSampleViewController.h"

@implementation LayerSampleViewController

// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
 UIView *rootView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 1024, 768)];
rootView.backgroundColor = [UIColor whiteColor];
self.view = rootView;
 [rootView release];

 //加载layer

backLayer = [CALayer layer];
backLayer.backgroundColor = [UIColor orangeColor].CGColor;
backLayer.bounds = CGRectMake(10, 10, 1004, 728); //设置layer的区域
backLayer.position = CGPointMake(1024/2, 768/2-10); //设置layer坐标
 [self.view.layer addSublayer:backLayer];

}

// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
 return interfaceOrientation == UIInterfaceOrientationLandscapeLeft;
}

- (void)didReceiveMemoryWarning {
 // Releases the view if it doesn't have a superview.
 [super didReceiveMemoryWarning];

 // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
 // Release any retained subviews of the main view.
 // e.g. self.myOutlet = nil;
}

- (void)dealloc {
 [super dealloc];
}

@end

#import <QuartzCore/QuartzCore.h>
LayerSampleViewController.m文件，代码：
//
//  LayerSampleViewController.m
//  LayerSample
//
//  Created by jordy on 11-3-28.
//  Copyright 2011 vsp. All rights reserved.
//

#import "LayerSampleViewController.h"

@implementation LayerSampleViewController

// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
    UIView *rootView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 1024, 768)];
    rootView.backgroundColor = [UIColor whiteColor];
    self.view = rootView;
    [rootView release];

    //加载layer

    backLayer = [CALayer layer];
    backLayer.backgroundColor = [UIColor orangeColor].CGColor;
    backLayer.bounds = CGRectMake(10, 10, 1004, 728); //设置layer的区域
    backLayer.position = CGPointMake(1024/2, 768/2-10); //设置layer坐标
    [self.view.layer addSublayer:backLayer];

}

// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    return interfaceOrientation == UIInterfaceOrientationLandscapeLeft;
}

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (void)dealloc {
    [super dealloc];
}

@end

运行程序：

为了区分背景UIView，我将UIView的背景色设置为白色，backLayer的背景色设置为橘黄色。

上图是一个矩形区域，如果设置矩形的四个角是椭圆角，可以添加属性：

backLayer.cornerRadius = 20.0; //矩形椭圆角的弧度半径

运行程序后，效果如图：

添加带阴影的子Layer（层）,代码：

 //添加子layer
CALayer *cyanLayer = [CALayer layer];
cyanLayer.backgroundColor = [UIColor cyanColor].CGColor;
cyanLayer.bounds = CGRectMake(0, 0, 300, 300);
cyanLayer.position = CGPointMake(180, 180);
cyanLayer.shadowOffset = CGSizeMake(0, 3); //设置阴影的偏移量
cyanLayer.shadowRadius = 10.0; //设置阴影的半径
cyanLayer.shadowColor = [UIColor blackColor].CGColor; //设置阴影的颜色为黑色
cyanLayer.shadowOpacity = 0.9; //设置阴影的不透明度

[backLayer addSublayer:cyanLayer];

 //添加子layer
CALayer *cyanLayer = [CALayer layer];
cyanLayer.backgroundColor = [UIColor cyanColor].CGColor;
cyanLayer.bounds = CGRectMake(0, 0, 300, 300);
cyanLayer.position = CGPointMake(180, 180);
cyanLayer.shadowOffset = CGSizeMake(0, 3); //设置阴影的偏移量
cyanLayer.shadowRadius = 10.0;  //设置阴影的半径
cyanLayer.shadowColor = [UIColor blackColor].CGColor; //设置阴影的颜色为黑色
cyanLayer.shadowOpacity = 0.9; //设置阴影的不透明度

[backLayer addSublayer:cyanLayer];

运行效果图：

给子Layer添加图片

//添加子image layer
UIImage *image = [UIImage imageNamed:@"feiche.jpg"];
CALayer *imageLayer = [CALayer layer];
imageLayer.frame = CGRectMake(100, 100, image.size.width, image.size.height);
imageLayer.contents = (id) image.CGImage;
imageLayer.shadowOffset = CGSizeMake(0, 3); //设置阴影的偏移量
imageLayer.shadowRadius = 10.0; //设置阴影的半径
imageLayer.shadowColor = [UIColor blackColor].CGColor; //设置阴影的颜色为黑色
imageLayer.shadowOpacity = 0.9; //设置阴影的不透明度

[backLayer addSublayer:imageLayer];

//添加子image layer
UIImage *image = [UIImage imageNamed:@"feiche.jpg"];
CALayer *imageLayer = [CALayer layer];
imageLayer.frame = CGRectMake(100, 100, image.size.width, image.size.height);
imageLayer.contents = (id) image.CGImage;
imageLayer.shadowOffset = CGSizeMake(0, 3); //设置阴影的偏移量
imageLayer.shadowRadius = 10.0;  //设置阴影的半径
imageLayer.shadowColor = [UIColor blackColor].CGColor; //设置阴影的颜色为黑色
imageLayer.shadowOpacity = 0.9; //设置阴影的不透明度

[backLayer addSublayer:imageLayer];

运行效果，

图片加边框，代码：

imageLayer.borderColor = [UIColor grayColor].CGColor;  //边框颜色
imageLayer.borderWidth = 2.0;  //边框宽度

imageLayer.borderColor = [UIColor grayColor].CGColor;  //边框颜色
imageLayer.borderWidth = 2.0;  //边框宽度

运行效果：

设置图片为椭圆角，代码：

imageLayer.cornerRadius = 10.0;  //设置layer圆角半径
imageLayer.masksToBounds = YES;  //隐藏边界

imageLayer.cornerRadius = 10.0;  //设置layer圆角半径
imageLayer.masksToBounds = YES;  //隐藏边界

运行效果：

但是由于设置masksToBounds 属性为true所以Layer的阴影效果也就没有了。

之前我都是将图片另外在做有阴影效果的图片，这样显的比较真实，如果阴影部分只是填充边框即可，可以采用两个Layer来实现阴影效果，代码：

UIImage *image = [UIImage imageNamed:@"feiche.jpg"];
//阴影layer
CALayer *shadowLayer = [CALayer layer];
shadowLayer.frame = CGRectMake(100, 100, image.size.width, image.size.height);
shadowLayer.backgroundColor = [UIColor blueColor].CGColor;
shadowLayer.shadowOffset = CGSizeMake(0, 3);
shadowLayer.cornerRadius = 10.0;
shadowLayer.shadowRadius = 10.0;
shadowLayer.shadowColor = [UIColor blackColor].CGColor; //设置阴影的颜色为黑色
shadowLayer.shadowOpacity = 1.0; //设置阴影的不透明度
[backLayer addSublayer:shadowLayer];

//添加子image layer
CALayer *imageLayer = [CALayer layer];
imageLayer.frame = CGRectMake(100, 100, image.size.width, image.size.height);
imageLayer.contents = (id) image.CGImage;
imageLayer.cornerRadius = 10.0;  //设置layer圆角半径
imageLayer.masksToBounds = YES;  //隐藏边界
imageLayer.borderColor = [UIColor grayColor].CGColor;  //边框颜色
imageLayer.borderWidth = 2.0;
[backLayer addSublayer:imageLayer];

UIImage *image = [UIImage imageNamed:@"feiche.jpg"];
//阴影layer
CALayer *shadowLayer = [CALayer layer];
shadowLayer.frame = CGRectMake(100, 100, image.size.width, image.size.height);
shadowLayer.backgroundColor = [UIColor blueColor].CGColor;
shadowLayer.shadowOffset = CGSizeMake(0, 3);
shadowLayer.cornerRadius = 10.0;
shadowLayer.shadowRadius = 10.0;
shadowLayer.shadowColor = [UIColor blackColor].CGColor; //设置阴影的颜色为黑色
shadowLayer.shadowOpacity = 1.0; //设置阴影的不透明度
[backLayer addSublayer:shadowLayer];

//添加子image layer
CALayer *imageLayer = [CALayer layer];
imageLayer.frame = CGRectMake(100, 100, image.size.width, image.size.height);
imageLayer.contents = (id) image.CGImage;
imageLayer.cornerRadius = 10.0;  //设置layer圆角半径
imageLayer.masksToBounds = YES;  //隐藏边界
imageLayer.borderColor = [UIColor grayColor].CGColor;  //边框颜色
imageLayer.borderWidth = 2.0;
[backLayer addSublayer:imageLayer];

运行后效果：

------转自http://blog.csdn.net/linzhiji/article/details/6748207