ios通过按钮点击异步加载图片

比较原始的方法：
复制代码代码如下:
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

方法二：
复制代码代码如下:
@interface UIButton （AsyncImage）
//size by point
- （void）setImageFromURL:（NSString *）urlString adjustToSize:（CGSize）size completion:（void （^）（void））completion logo:（UIImage *）logoImage;
@end
@implementation UIButton （AsyncImage）
- （void）setImageFromURL:（NSString *）urlString adjustToSize:（CGSize）size completion:（void （^）（void））completion logo:（UIImage *）logoImage
{
    dispatch_async（dispatch_get_global_queue（DISPATCH_QUEUE_PRIORITY_DEFAULT, 0）, ^{
        UIImage *image = nil;
        NSURL *url = [NSURL URLWithString:urlString];
        NSData *data = [NSData dataWithContentsOfURL:url];
        image = [UIImage imageWithData:data];
        if （image） {
            if （！CGSizeEqualToSize（size, CGSizeZero）） {
                image = [UIImage imageWithCGImage:image.CGImage scale:[self scaleImage:image adjustToSize:size] orientation:image.imageOrientation];
            }
            if （logoImage） {
                image = [self addLogoImage:logoImage toImage:image];
            }
            dispatch_async（dispatch_get_main_queue（）, ^{
                [self setImage:image forState:UIControlStateNormal];
                completion（）;
            }）;
        }
        else {
            NSLog（@"async load error."）;
        }
    }）;
}
// 缩放图片以适应按钮大小
- （CGFloat）scaleImage:（UIImage *）image adjustToSize:（CGSize）size
{
    CGFloat xScale = size.width / image.size.width;
    CGFloat yScale = size.height / image.size.height;
    return 1.0 / MIN（xScale, yScale）;
}
- （UIImage *）addLogoImage:（UIImage *）logo toImage:（UIImage *）img
{
    //get image width and height
    CGFloat scale = [UIScreen mainScreen].scale;
    int w = scale * img.size.width;
    int h = scale * img.size.height;
    int logoWidth = logo.scale * logo.size.width;
    int logoHeight = logo.scale * logo.size.height;
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB（）;
    //create a graphic context with CGBitmapContextCreate
    CGContextRef context = CGBitmapContextCreate（NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst）;
    CGContextDrawImage（context, CGRectMake（0, 0, w, h）, img.CGImage）;
    CGContextDrawImage（context, CGRectMake（w - logoWidth, 0, logoWidth, logoHeight）, [logo CGImage]）;
    CGImageRef imageMasked = CGBitmapContextCreateImage（context）;
    CGContextRelease（context）;
    CGColorSpaceRelease（colorSpace）;
    return [UIImage imageWithCGImage:imageMasked scale:scale orientation:img.imageOrientation];
}
@end

方法三：

#import <Foundation/Foundation.h>#import "StringUtils.h"@interface ImageManager : NSObject{NSMutableDictionary *_imageDict;NSMutableArray *_imageArr;}@property（nonatomic, strong） NSString *httpUrl;@property（nonatomic, strong） NSMutableDictionary *imageDict;@property（nonatomic, assign） dispatch_queue_t networkQueue;+ （ImageManager *） sharedInstance;- （void）asyncImage:（NSString *）imageName imageView:（UIImageView *）imageView;//插队- （void）asyncImageInsert:（NSString *）imageName imageView:（UIImageView *）imageView insert:（BOOL）insert;//不要在下载之前的数据- （void）asyncImageCleanOld:（NSString *）imageName imageView:（UIImageView *）imageView cleanOld:（BOOL）cleanOld;@end

实现文件：

//// ImageManager.m// myb-ios//// Created by warrior gao on 13-6-5.// Copyright （c） 2013年 51myb. All rights reserved.//#import "ImageManager.h"@interface ImageManager（）@end@implementation ImageManager//缓存图片的最大数量static int counter = 0;@synthesize imageDict = _imageDict;//Singleton + （ImageManager *）sharedInstance{static id instance;static dispatch_once_t onceToken;dispatch_once（&onceToken, ^{instance = self.new;}）;return instance;}- （id）init{if（（self = [super init]））{self.networkQueue = dispatch_queue_create（"com.warrior.network.image", nil）;_imageDict = [[NSMutableDictionary alloc] init];_imageArr = [[NSMutableArray alloc] init];}return self;}- （NSString *） fileFullPath:（NSString *）fileName{NSString *cachePath = [NSSearchPathForDirectoriesInDomains（NSCachesDirectory, NSUserDomainMask, YES） objectAtIndex:0];NSString *fileFullPath = [NSString stringWithFormat:@"%@/%@",cachePath,fileName];return fileFullPath;}//不要在下载之前的数据- （void）asyncImageCleanOld:（NSString *）imageName imageView:（UIImageView *）imageView cleanOld:（BOOL）cleanOld{if（cleanOld）{[_imageArr removeAllObjects];}[self asyncImage:imageName imageView:imageView];}//插队，优先- （void）asyncImageInsert:（NSString *）imageName imageView:（UIImageView *）imageView insert:（BOOL）insert{if（[StringUtils isEmpty:imageName]）{return;}NSData *data = [NSData dataWithContentsOfFile:[self fileFullPath:[imageName stringByReplacingOccurrencesOfString:@"/" withString:@"-"]]];if（data == nil）{[_imageDict setValue:imageView forKey:imageName];if（insert）{[_imageArr insertObject:imageName atIndex:0];}else{[_imageArr addObject:imageName];}[self cacheImage];} else {[imageView setImage:[UIImage imageWithData:data]];}}//正常，附加到后面- （void）asyncImage:（NSString *）imageName imageView:（UIImageView *）imageView{[self asyncImageInsert:imageName imageView:imageView insert:NO];}//异步缓存图片到本地，最多有两个线程-（void）cacheImage{for （; counter < 2 && _imageArr.count > 0; counter++）{NSString *imageName = nil;@synchronized（self）{imageName = [[_imageArr objectAtIndex:0] copy];[_imageArr removeObjectAtIndex:0];}if（imageName == nil） continue;dispatch_async（self.networkQueue, ^{NSLog（@"Starting: %@", imageName）;UIImage *avatarImage = nil;NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"%@%@",self.httpUrl, imageName]];NSData *responseData = [NSData dataWithContentsOfURL:url];if（responseData.length > 0）{[responseData writeToFile:[self fileFullPath:[imageName stringByReplacingOccurrencesOfString:@"/" withString:@"-"]] atomically:NO];avatarImage = [UIImage imageWithData:responseData];NSLog（@"Finishing: %@", imageName）;if （avatarImage） {dispatch_async（dispatch_get_main_queue（）, ^{UIImageView *imageView = [_imageDict objectForKey:imageName];if（imageView ！= nil && avatarImage ！= nil）{[imageView setImage:avatarImage];}[_imageDict removeObjectForKey:imageName];[imageName release];}）;}}counter--;[self cacheImage];}）;}}@end

以上所述就是本文的全部内容了，希望大家能够喜欢。