iOS编程------UITableView中图片的异步下载 / KVO监测Model图片下载

////  AppDelegate.h//  UI17_imageDownLoader////  Created by l on 15/9/23.//  Copyright (c) 2015年 . All rights reserved.//#import <UIKit/UIKit.h>@interface AppDelegate : UIResponder <UIApplicationDelegate>@property (strong, nonatomic) UIWindow *window;@end////  AppDelegate.m//  UI17_imageDownLoader////  Created by l on 15/9/23.//  Copyright (c) 2015年 . All rights reserved.//#import "AppDelegate.h"#import "ImageDownloader.h"@interface AppDelegate ()<ImageDownloaderDelegate>@property (nonatomic, retain) UIImageView *imageView;@end@implementation AppDelegate- (void)dealloc{    [_window release];    [_imageView release];    [super dealloc];}//实现自定义协议方法- (void)imageDownloader:(ImageDownloader *)downloader didFinishLoading:(UIImage *)image{    _imageView.image = image;}- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];    // Override point for customization after application launch.    self.window.backgroundColor = [UIColor whiteColor];    [self.window makeKeyAndVisible];    //一. 异步图片下载类    _imageView = [[UIImageView alloc] initWithFrame:(CGRectMake(80, 100, 250, 300))];    //图片同步下载:  (同步网络请求,会卡线程)//    _imageView.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://picm.photophoto.cn/015/037/003/0370032259.jpg"]]];    //--------------//    //代理方法:    [ImageDownloader imageDownloaderWithURLString:@"http://d.hiphotos.baidu.com/image/pic/item/d0c8a786c9177f3ec4c5de0c72cf3bc79f3d5639.jpg" delegate:self];    //-------------//    //block://    NSString *url = @"http://img.sootuu.com/vector/2006-4/200642011196982.jpg";//////    [ImageDownloader sendAsynchonousURLString:url completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {//        //        //获取到回调的data数据,赋值给imageView.image//        _imageView.image = [UIImage imageWithData:data];//    }];////    //加载_imageView    [self.window addSubview:_imageView];    return YES;}@end////////////////////////////////////////////////////////////////////////  ImageDownloader.h//  UI17_imageDownLoader////  Created by l on 15/9/23.//  Copyright (c) 2015年 . All rights reserved.//此为异步图片下载类,封装了系统的connection , 异步网络请求.//采用delegate 和 block 两种方式.#import <Foundation/Foundation.h>#import <UIKit/UIKit.h>//定义block类型typedef void (^CompletionHandler)(NSURLResponse *response, NSData *data, NSError *error);@class ImageDownloader;//定义协议@protocol ImageDownloaderDelegate <NSObject, NSURLConnectionDelegate, NSURLConnectionDataDelegate>@optional//图片下载完成之后触发- (void)imageDownloader:(ImageDownloader *)downloader didFinishLoading:(UIImage *)image;//图片下载失败的时候触发- (void)imageDownloader:(ImageDownloader *)downloader didFailWithError:(NSError *)error;@end@interface ImageDownloader : NSObject@property (nonatomic, copy) NSString *urlString;//图片网络地址//1.delegate@property (nonatomic, assign) id<ImageDownloaderDelegate> delegate;//自定义初始化方法- (instancetype)initWithURLString:(NSString *)urlString delegate:(id<ImageDownloaderDelegate>) delegate;//便利构造器+ (ImageDownloader *)imageDownloaderWithURLString:(NSString *)urlString delegate:(id<ImageDownloaderDelegate>) delegate;+ (void)sendAsynchonousURLString:(NSString *)urlString completionHandler:(CompletionHandler)handler;@end////  ImageDownloader.m//  UI17_imageDownLoader////  Created by l on 15/9/23.//  Copyright (c) 2015年 . All rights reserved.//#import "ImageDownloader.h"@interface ImageDownloader ()<NSURLConnectionDelegate, NSURLConnectionDataDelegate>@property (nonatomic, retain) NSMutableData *receiveData;@end@implementation ImageDownloader- (void)dealloc{    [_urlString release];    [_receiveData release];    [super dealloc];}//重写初始化方法(自定义初始化方法)- (instancetype)initWithURLString:(NSString *)urlString delegate:(id<ImageDownloaderDelegate>) delegate{    self = [super init];    if (self) {        self.urlString = urlString;        self.delegate = delegate;        //进行网络请求        NSURL *url = [NSURL URLWithString:_urlString];        NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url cachePolicy:0 timeoutInterval:10];        //异步网络请求方式,代理        [NSURLConnection connectionWithRequest:request delegate:self];    }    return self;}//便利构造器+ (ImageDownloader *)imageDownloaderWithURLString:(NSString *)urlString delegate:(id<ImageDownloaderDelegate>) delegate{    return [[[ImageDownloader alloc] initWithURLString:urlString delegate:delegate] autorelease];}- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{    self.receiveData = [NSMutableData data];}- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{    [self.receiveData appendData:data];}- (void)connectionDidFinishLoading:(NSURLConnection *)connection{    //数据接收完成后,把数据通过协议的方法,作为方法参数,传递给delegate    UIImage *image = [UIImage imageWithData:self.receiveData];    if (_delegate != nil && [_delegate respondsToSelector:@selector(imageDownloader:didFinishLoading:)]) {        [_delegate imageDownloader:self didFinishLoading:image];    }}- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{    if (_delegate != nil && [_delegate respondsToSelector:@selector(imageDownloader:didFailWithError:)]) {        [_delegate imageDownloader:self didFailWithError:error];    }}//block+ (void)sendAsynchonousURLString:(NSString *)urlString completionHandler:(CompletionHandler)handler{    NSURL *url = [NSURL URLWithString:urlString];    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {        //把参数通过block的参数传递出去        handler(response, data, connectionError);    }];}@end