//从网络下载图片  -(UIImage *) getImageFromURL:(NSString *)fileURL {      NSLog(@"执行图片下载函数");      UIImage * result;        NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];      result = [UIImage imageWithData:data];        return result;  }    //将所下载的图片保存到本地  -(void) saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {      if ([[extension lowercaseString] isEqualToString:@"png"]) {          [UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];      } else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {          [UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];      } else {          //ALog(@"Image Save Failed\\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);          NSLog(@"文件后缀不认识");      }  }    //读取本地保存的图片  -(UIImage *) loadImage:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {      UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension]];        return result;  }    //从网络下载图片，保存，并用 UIImageView 从保存中显示  NSString * documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];      NSLog(@"保存路径:%@",documentsDirectoryPath);      //Get Image From URL      UIImage * imageFromURL = [self getImageFromURL:@"http://file.duteba.com/phone/2009/04/5/ftGxL8kcUL.jpg"];        //Save Image to Directory      [self saveImage:imageFromURL withFileName:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];        //Load Image From Directory      UIImage * imageFromWeb = [self loadImage:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];      [img setImage:imageFromWeb];        //取得目录下所有文件名      NSArray *file = [[[NSFileManager alloc] init] subpathsAtPath:documentsDirectoryPath];      //NSLog(@"%d",[file count]);      NSLog(@"%@",file);  //该片段来自于http://outofmemory.cn