摘要:本文将带你了解IOS源码之通过按钮点击异步加载图片的方法,希望本文对大家学IOS有所帮助。
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:
#<d>import</d> <Foundation/Foundation.h> #<d>import</d> "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. // #<d>import</d> "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]; }); } }
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