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- (IBAction)onClick:(id)sender {    NSMutableDictionary *imageDic = [[NSMutableDictionary alloc] init];    //获取本地沙箱的缓存路径    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);    NSString *cachesDirectory = paths[0];    NSString *downloadPath = [cachesDirectory stringByAppendingPathComponent:@"test1.jpg"];        //先从本地获取缓存图片    UIImage *image = [UIImage imageWithContentsOfFile:downloadPath];        //如果从本地缓存中获取为空，那么再从应用资源中获取一次    if (image == nil) {        image = [UIImage imageNamed:@"test1.jpg"];    }        if (nil != image) {        [imageDic setObject:image forKey:@"image"];        NSLog(@"缓存有图片！");        _imageView1.image = image;    }        //如果本地缓存图片为空，则远程请求，并缓存到本地    if(image == nil) {                NSString *path = [[NSString alloc] initWithFormat:@"/service/download.php?email=%@&FileName=test1.jpg",@"gs.654586026@qq.com"];        path = [path stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];            MKNetworkEngine *engine = [[MKNetworkEngine alloc] initWithHostName:@"51work6.com" customHeaderFields:nil];            MKNetworkOperation *downloadOperation = [engine operationWithPath:path params:nil httpMethod:@"POST"];        [downloadOperation addDownloadStream:[NSOutputStream outputStreamToFileAtPath:downloadPath append:TRUE]];            [downloadOperation onDownloadProgressChanged:^(double progress) {        NSLog(@"download progress: %.2f%%", progress*100.0);        _progressView.progress = progress;        }];            [downloadOperation addCompletionHandler:^(MKNetworkOperation *operation) {                NSLog(@"download file finished!");        UIImage *image = [UIImage imageWithContentsOfFile:downloadPath];        _imageView1.image = image;                    } errorHandler:^(MKNetworkOperation *errorOp, NSError* err) {            NSLog(@"MKNetwork请求错误 : %@", [err localizedDescription]);        }];    [engine enqueueOperation:downloadOperation];    }}