下载内部图像后调整 UICollectionView 单元格的大小 [英] Resize UICollectionView cells after image inside has been downloaded

问题描述

我正在构建一个 UICollectionView，我的自定义单元格将包含两个标签和一个图像.

I'm building a UICollectionView and my custom cells will contain two labels and one image.

每张图片都是异步下载的，所以在下载完成之前我不知道它的大小.下载后，我想调整每个单元格以重新布局其内容和框架以适应刚刚下载的图像的高度.

Each image is downloaded asynchronously so I don't know it's size until the download it's complete. Once is downloaded, I want to adapt each cell to re-layout it's content and frame to fit in height the image just downloaded.

作为 UICollectionViewLayout，我使用的是 CHTCollectionViewWaterfallLayout

要异步下载图像，我使用 SDWebImage，如下所示:

To download the image asynchronously I'm using SDWebImage, like this:

    [cell.imageView setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
                   placeholderImage:[UIImage imageNamed:@"placeholder.png"]
                          completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) 
                                {... some completion code here ...}];

问题:

在下载图像后立即调整每个 UICollectionViewCell 大小的正确方法是什么?

What is the right approach to resize each UICollectionViewCell right after the image is downloaded?

推荐答案

当图像返回时，您应该能够使动画块中的集合视图布局无效.如果不止一张图片一次完成，事情可能会变得有点复杂，但这应该可以:

You should just be able to invalidate your collection view layout in an animation block when the image comes back. Things might get a little complicated if more than one image finishes completion at once, but this should work:

[cell.imageView setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
               placeholderImage:[UIImage imageNamed:@"placeholder.png"]
                      completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType)^{
                          [UIView animateWithDuration:0.3f animations:^{
                              [self.collectionView.collectionViewLayout invalidateLayout];
                          }];
                      }];

然后在适当的委托方法中返回不同的大小.

Then just return a different size in the appropriate delegate method.

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    return /* a different size if the image is done downloading yet */;
}

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