Question

我在一个阵列中存储了大约100 UIImage个。我知道有一个内存使用问题最终导致应用程序崩溃，特别是在旧设备（iPhone 4s）上。在用户体验方面，UIImages上存储了所有DocumentsDirectory - 不是一个选项（需要太长时间）。所以我在考虑“合并”这两种方法。等到我收到内存使用警告，停止将图像保存到我的阵列，然后开始存储在磁盘上。我找不到处理Memory leak/warning/usage call

的正确方法

 override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        print("memory warning")
    }

当我在真实设备上测试时，它只是崩溃 - 没有调用方法。有什么建议吗？

Answer 1

尝试使用图像缓存库。最受欢迎的比较是： https://bpoplauschi.wordpress.com/2014/03/21/ios-image-caching-sdwebimage-vs-fastimage/

我的经验：SDWebImage最适合通常来自互联网的URL源图像，而Haneke适用于基于ID的图像，例如视频生成的缩略图。两者都可以在CocoaPods中找到。

SDWebImage使用CoreData SQLite DB进行URL缓存。它没有“手工制作”图像的方法，但在从REST下载互联网图像的REST应用程序中广泛流行。我刚刚在AppStore MyHairDressers应用程序中发布它。 FastCache使用文件进行URL缓存。但它也喜欢SDWebImage不适合缓存“手工制作”图像。两者都非常适合通过URL下载的图像。 Haneke不仅可以通过URL按自定义ID存储图像。但是像FastCache一样需要一些配置。以下是一些配置的代码：

``

HNKCacheFormat *cacheFormatThumbnail = [[HNKCache sharedCache] formats][CACHE_FORMAT_THUMBNAIL];
        if (cacheFormatThumbnail == nil)
        {
            cacheFormatThumbnail = [[HNKCacheFormat alloc] initWithName:CACHE_FORMAT_THUMBNAIL];
            cacheFormatThumbnail.size = CGSizeMake(100.0f, 56.0f);
            cacheFormatThumbnail.scaleMode = HNKScaleModeAspectFit;
            cacheFormatThumbnail.compressionQuality = 0.5f;
            cacheFormatThumbnail.diskCapacity = 10 * 1024 * 1024; // 10MB
            cacheFormatThumbnail.preloadPolicy = HNKPreloadPolicyLastSession;
            [[HNKCache sharedCache] registerFormat:cacheFormatThumbnail];
        }
        HNKCacheFormat *cacheFormatPhoto = [[HNKCache sharedCache] formats][CACHE_FORMAT_PHOTO];
        if (cacheFormatPhoto == nil)
        {
            cacheFormatPhoto = [[HNKCacheFormat alloc] initWithName:CACHE_FORMAT_PHOTO];
            CGFloat scale = [[UIScreen mainScreen] scale];
            cacheFormatPhoto.size = CGSizeMake(1280.0f * scale, 720.0f * scale);
            cacheFormatPhoto.scaleMode = HNKScaleModeAspectFit;
            cacheFormatPhoto.compressionQuality = 0.5f;
            cacheFormatPhoto.diskCapacity = 50 * 1024 * 1024; // 50MB
            cacheFormatPhoto.preloadPolicy = HNKPreloadPolicyNone;
            [[HNKCache sharedCache] registerFormat:cacheFormatPhoto];
        }

``

以下是创建缓存图像的示例（TableViewCell包含带缩略图的CollectionView）：

``

- (UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    VideoCell *cell = (VideoCell *)[super tableView:tableView cellForRowAtIndexPath:indexPath];
    VideoAsset *asset = (VideoAsset *)[self.fetchedResultsController objectAtIndexPath:indexPath];
    if ([asset thumbnails] == 0)
    {
        MBProgressHUD *hud = [[MBProgressHUD alloc] initWithView:[cell thumbnails]];
        hud.removeFromSuperViewOnHide = YES;
        [[cell thumbnails] addSubview:hud];
        hud.labelText = NSLocalizedString(@"H11",nil);
        [hud show:YES];
        CGFloat scale = [[UIScreen mainScreen] scale];
        CGSize size = CGSizeMake(100.0f * scale, 56.0f *scale);
        __weak typeof(cell) weakCell = cell;
        [asset generateThumbnails:self->thumbnailsCount offset:self->thumbnailsOffset size:size completion:^(NSArray *thumbnails) {
            dispatch_async(dispatch_get_main_queue(), ^{
                [hud hide:YES];
            });
            if ((thumbnails != nil) && ([thumbnails count] > 0))
            {
                HNKCache *cache = [HNKCache sharedCache];
                NSUInteger n = 0;
                NSUInteger keyHash = [[[asset assetURL] absoluteString] hash];
                for (UIImage *image in thumbnails)
                {
                    [cache setImage:image forKey:[NSString stringWithFormat:@"%lu@%i",(unsigned long)keyHash,(int)(n++)] formatName:CACHE_FORMAT_THUMBNAIL];
                    dispatch_async(dispatch_get_main_queue(), ^{
                        if (weakCell != nil)
                        {
                            __strong typeof(cell) strongCell = weakCell;
                            [[strongCell thumbnails] reloadData];
                        }
                    });
formatName:CACHE_FORMAT_PHOTO];
                }
            }
        }];
    }
    return (UITableViewCell *)cell;
}

``

并使用（表视图单元格中集合的集合视图单元格）：

``

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    ThumbnailCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];
    NSString *key = [NSString stringWithFormat:@"%lu@%i",(unsigned long)[[[(VideoAsset *)self->_selectedObject assetURL] absoluteString] hash],(int)[indexPath item]];
    [cell setKey:key];
    [cell setTag:[indexPath item]];
    __weak typeof(cell) weakCell = cell;
    [[HNKCache sharedCache] fetchImageForKey:key formatName:CACHE_FORMAT_THUMBNAIL success:^(UIImage *image) {
        [[weakCell image] setImage:image];
    } failure:^(NSError *error) {
        if ([[error domain] isEqualToString:HNKErrorDomain] && ([error code] == HNKErrorImageNotFound))
        {
            [[weakCell image] setImage:[UIImage imageNamed:@"movieplaceholder"]];
        }
        else [error reportError];
    }];
    return cell;
}

``

使用大量UIImage时的内存问题

1 个答案: