imageDownloader

.h

#import <UIKit/UIKit.h>

@protocol imageDownloadDelegate <NSObject>

@optional

-(void)imageDownloadWithImage:(UIImage *)image;

@end

// 声明一个block 参数类型是UIImage 返回值是void 别名Result

typedef void(^Result)(UIImage *img);

@interface ImageDownload : NSObject

#pragma mark - 声明方法  被调用后直接下载

+(void)imageDownloadWithUrlStr:(NSString *)urlStr

                      delegate:(id<imageDownloadDelegate>)delegate;

#pragma mark - 声明方法 使用block的方式

+(void)imageDownloadWithUrlStr:(NSString *)urlStr

                        result:(Result)result;

@end

 

.m

#import "ImageDownload.h"

@implementation ImageDownload

#pragma mark - 实现方法 代理

+(void)imageDownloadWithUrlStr:(NSString *)urlStr

                      delegate:(id<imageDownloadDelegate>)delegate

{

    NSURL *url = [NSURL URLWithString:urlStr];

    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue new]autorelease] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

        UIImage *image = [UIImage imageWithData:data];

        dispatch_sync(dispatch_get_main_queue(),^{

            if (delegate!=nil && [delegate respondsToSelector:@selector(imageDownloadWithImage:)]) {

                [delegate imageDownloadWithImage:image];

            }

        });

    }];

}

#pragma mark - 实现方法  block 方式

+(void)imageDownloadWithUrlStr:(NSString *)urlStr

                        result:(Result)result

{

    NSURL *url = [NSURL URLWithString:urlStr];

    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue new]autorelease] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

        UIImage *image = [UIImage imageWithData:data];

        

        // 回到主线程使用block

        dispatch_sync(dispatch_get_main_queue(), ^{

           // block 调用

            result(image);

        });

    }];

}

再去 ViewController 

- (IBAction)buttonAction:(UIButton *)sender

{

    /*

   //http://img4.duitang.com/uploads/item/201208/10/20120810091225_hvA2r.thumb.700_0.jpeg

    //1 NSURL

    NSURL *url = [NSURL URLWithString:@"http://img4.duitang.com/uploads/item/201208/10/20120810091225_hvA2r.thumb.700_0.jpeg"];

    

    //2 NSURLREQUEST

    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    

    //3 NSURLConnection

    

    __block ViewController *weakSelf = self;

    [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue new]autorelease] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

        //4 获取data数据  转为UIImage类型

        UIImage *image = [UIImage imageWithData:data];

        //5 回到主界面 刷新数据

        dispatch_sync(dispatch_get_main_queue(),^{

            weakSelf.imageView.image = image;

        });

    }];

     */

    // 直接发送消息 设置代理

    // [ImageDownload imageDownloadWithUrlStr:@"http://img4.duitang.com/uploads/item/201208/10/20120810091225_hvA2r.thumb.700_0.jpeg" delegate:self];

    

    // 使用block

    __block ViewController *weakSelf = self;

    [ImageDownload imageDownloadWithUrlStr:@"http://img4.duitang.com/uploads/item/201208/10/20120810091225_hvA2r.thumb.700_0.jpeg" result:^(UIImage *img)

     {

         // 将block中参数显示到UIImageView上

         weakSelf.imageView.image = img;

     }];

}

@end