我将如何停止重复在我的表视图中加载图像？

这是我的代码显示从服务器的图像。 加载图像后，向下滚动然后再向后滚动，图像消失，再次加载之前还有另一个延迟时间。

dispatch_async(kBgQueue, ^{ NSString *profileImageStr = [[displayItems objectAtIndex:indexPath.row] objectForKey:@"image_url"]; NSURL* profileImgURL = [NSURL URLWithString:profileImageStr]; NSData *profileImgData = [NSData dataWithContentsOfURL:profileImgURL]; NSString *postPhotoStr = [[displayItems objectAtIndex:indexPath.row] objectForKey:@"image_url"]; NSURL *postImgURL = [NSURL URLWithString:postPhotoStr]; NSData *postImageData = [NSData dataWithContentsOfURL:postImgURL]; dispatch_async(dispatch_get_main_queue(), ^{ if (postImageData && profileImgData != nil) { cell.thumbnailImg.image = [UIImage imageWithData:profileImgData]; cell.bgImgView.image = [UIImage imageWithData:postImageData]; }else { cell.thumbnailImg.image = [UIImage imageNamed:@"noimage.jpg"]; cell.bgImgView.image = [UIImage imageNamed:@"noimage.jpg"]; } }); } ); return cell; 

Answer 1

我认为你需要实现图像caching。 将图像存储在NSCache 。

 //instance NSCache *imageCache; - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { NSString *simpleTableIdentifier=nil; if([objRepresentative.team count]>0) { simpleTableIdentifier=[NSString stringWithFormat:@"%@",[objRepresentative.employeeID objectAtIndex:indexPath.row]]; } else simpleTableIdentifier = @"ContactTableCell"; ContactTableCell *cell = (ContactTableCell *)[tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier]; if (cell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"ContactTableCell" owner:self options:nil]; cell = [nib objectAtIndex:0]; NSString *photoString=[NSString stringWithFormat:@"http://www.foo.com/%@",[searchPhoto objectAtIndex:indexPath.row]]; UIImage *image = [imageCache objectForKey:photoString]; if (image) { cell.ProfilePicture.image=image; } else { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ NSURL *url = [NSURL URLWithString:[photoString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]; UIImage *image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:url]]; if(image) { dispatch_async(dispatch_get_main_queue(), ^{ UIImage *small = [self imageWithImage:image scaledToSize:CGSizeMake(100, 100)]; cell.ProfilePicture.image=small; }); [imageCache setObject:image forKey:photoString]; } else cell.ProfilePicture.image=[UIImage imageNamed:@"noPicture.png"]; }); } } return cell; }