iOS开发中通过点击按钮异步加载图片

AsyncImageView.h:
　　#import

　　@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：

　　?

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#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：

　　?

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// // 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