ios – 缓存图像和UICollectionView
发布时间:2020-12-15 01:43:41 所属栏目:百科 来源:网络整理
导读:我对Objective-C很新,所以希望这一切都有意义.我从服务器下载了图像,并将它们显示在collectionView cellForItemAtIndexPath:方法的图像视图中.我面临的问题是图像似乎不是缓存.看起来每次重复使用一个单元时,都会重新下载来自服务器的相关图像. 在我的viewD
我对Objective-C很新,所以希望这一切都有意义.我从服务器下载了图像,并将它们显示在collectionView cellForItemAtIndexPath:方法的图像视图中.我面临的问题是图像似乎不是缓存.看起来每次重复使用一个单元时,都会重新下载来自服务器的相关图像.
在我的viewDidLoad方法中,我正在创建一个NSMutableDictionary: imageDictionary = [[NSMutableDictionary alloc]initWithCapacity:50.0]; 从阅读文档和查看类似问题的答案,我认为这一点,加上以下代码就足够了.我已经在这里工作了几天,我知道有些东西我缺少或者我不理解的概念. #pragma mark - UICollectionView Data Source - (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section;{ NSLog(@"Begin retrieving photos"); return [self.photos count]; } -(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{ return 1; } - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath;{ CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MY_CELL" forIndexPath:indexPath]; cell.imageView.image = nil; if (cell.imageView.image == nil) { dispatch_queue_t downloadQueue = dispatch_queue_create("image downloader",NULL); dispatch_async(downloadQueue,^{ NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[self.photos objectAtIndex:indexPath.row] objectForKey:@"fullimage"]]]; UIImage *image = [UIImage imageWithData:data]; [imageDictionary setObject:image forKey:@"Image"]; dispatch_async(dispatch_get_main_queue(),^{ cell.imageView.image = [imageDictionary objectForKey:@"Image"]; [cell setNeedsDisplay]; }); }); } return cell; } 任何帮助将不胜感激.提前致谢. 解决方法
@yuf – 再次感谢方向. NSCache似乎让我得到了我追求的结果.这是正常工作的代码.如果有人有类似的问题,您可以将以下内容与我原来的问题进行比较.
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath;{ CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MY_CELL" forIndexPath:indexPath]; NSString *imageName = [[self.photos objectAtIndex:indexPath.row] objectForKey:@"fullimage"]; UIImage *image = [imageCache objectForKey:imageName]; if(image){ cell.imageView.image = image; } else{ cell.imageView.image = nil; dispatch_queue_t downloadQueue = dispatch_queue_create("image downloader",^{ NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[self.photos objectAtIndex:indexPath.row] objectForKey:@"fullimage"]]]; UIImage *image = [UIImage imageWithData:data]; dispatch_async(dispatch_get_main_queue(),^{ cell.imageView.image = image; }); [imageCache setObject:image forKey:imageName]; }); } return cell; } (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |