iOS开发之异步加载图片

来源：互联网发布：如何下载淘宝卖家版编辑：程序博客网时间：2024/05/16 12:20

比较原始的方法：

AsyncImageView.h:

#import <UIKit/UIKit.h>

@interface AsyncImageView : UIView

{

NSURLConnection* connection;

NSMutableData* data;

}

- (void)loadImageFromURL:(NSURL*)url;

@end

AsyncImageView.m:

#import "AsyncImageView.h"

@implementation AsyncImageView

- (id)initWithFrame:(CGRect)frame

{

self = [super initWithFrame:frame];

if(self) {

// Initialization code

}

returnself;

}

- (void)loadImageFromURL:(NSURL*)url {

if(connection!=nil) { [connection release]; }

if(data!=nil) { [data release]; }

NSURLRequest* request = [NSURLRequest requestWithURL:url

cachePolicy:NSURLRequestUseProtocolCachePolicy

timeoutInterval:60.0];

connection = [[NSURLConnection alloc]

initWithRequest:request delegate:self];

}

- (void)connection:(NSURLConnection *)theConnection

didReceiveData:(NSData *)incrementalData {

if(data==nil) {

data =

[[NSMutableData alloc] initWithCapacity:2048];

}

[data appendData:incrementalData];

}

- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection {

[connection release];

connection=nil;

if([[self subviews] count] > 0) {

[[[self subviews] objectAtIndex:0] removeFromSuperview];

}

UIImageView *imageView = [[[UIImageView alloc] initWithImage:[UIImage imageWithData:data]] autorelease];

imageView.contentMode = UIViewContentModeScaleAspectFit;

imageView.autoresizingMask = ( UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight );

[self addSubview:imageView];

imageView.frame = self.bounds;

[imageView setNeedsLayout];

[self setNeedsLayout];

[data release];

data=nil;

}

- (UIImage*) image {

UIImageView* iv = [[self subviews] objectAtIndex:0];

return[iv image];

}

- (void)dealloc {

[connection cancel];

[connection release];

[data release];

[super dealloc];

}

@end

使用：

AsyncImageView *asyncImage = [[AsyncImageView alloc] init];

asyncImage.frame = CGRectMake(100, point_y, 95, 95)

//圆角

[asyncImage.layer setMasksToBounds:YES];

[asyncImage.layer setCornerRadius:15];

[asyncImage loadImageFromURL:[NSURL URLWithString:@"www.istar.name/...."]];

不过发现一个好东东， SDWebImage，这个实在是太方便了
主页：https://github.com/rs/SDWebImage
1.下载下来放到project里面
2. 添加：MapKit.framework
3. #import “UIImageView+WebCache.h”
4. 使用：

UIImageView *asyncImage = [[UIImageView alloc] init];

[asyncImage setImageWithURL:[NSURL URLWithString:@www.istar.name/....]];

使用第三方库

EGOImageLoading是我在项目中用的比较多的一个第三方图片异步加载类，你们可以在git上找到并下载它，链接如下。另外提一下，
广为人知的下拉刷新EGORefreshTableHeaderView也是就是这个人写的。

https://github.com/enormego/EGOImageLoading
(下载后运行demo程序XCode会提示找不到EGOCache.h头文件，可以在这个地方下载https://github.com/enormego/EGOCache)

使用方法可以参照里面的demo程序，很简单，只要把ImageUrl告诉它，剩下的就什么都不用管了，它会帮你异步加载，还会做缓存处理...

?1234 // 设置默认占位图片 myEgoimageView.placeholderImage = [UIImage imageNamed:@"placeholder.png"]; // 告诉它图片的url地址, done myEgoimageView.imageURL = [NSURL URLWithString:@"http://simg.cocoachina.com/201111220746561330.jpg"];

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