Question

我正在水平集合视图中显示从服务器收到的动态图像。当我设置集合视图时，我设置了这个：

-(void)setupCollectionView{
[self setupPageControlView];
self.screensCollectionView.delegate=self;
self.screensCollectionView.dataSource=self;
[self.screensCollectionView registerNib:[UINib nibWithNibName:@"FGAppScreensCollectionViewItemCell" bundle:nil] forCellWithReuseIdentifier:@"screenCell"];


UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
[flowLayout setScrollDirection:UICollectionViewScrollDirectionHorizontal];
[flowLayout setMinimumInteritemSpacing:0.0f];
[flowLayout setMinimumLineSpacing:0.0f];
[flowLayout setItemSize:CGSizeMake(165, 255)];
//[self.screensCollectionView setPagingEnabled:YES];
[self.screensCollectionView setCollectionViewLayout:flowLayout];

}

对于cellForRowAtIndexPath我下载图片如下：

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
static NSString *cellIdentifier = @"screenCell";

FGAppScreensCollectionViewItemCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

NSURLRequest *urlRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:[self.imageURLArray objectAtIndex:indexPath.row]]];

UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
[spinner startAnimating];
[spinner setFrame:CGRectMake(50, 100, 20, 20)];
[cell.contentView addSubview:spinner];
[cell.screenImageView setImageWithURLRequest:urlRequest placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
    //STOP THE SPINNER
    for (UIView* view in [cell.contentView subviews]) {
        if ([view isKindOfClass:[UIActivityIndicatorView class]]) {
            [view removeFromSuperview];
        }
    }
    cell.screenImageView.image = image;

} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
    //
}];
[cell.screenImageView setImageWithURL:[NSURL URLWithString:[self.imageURLArray objectAtIndex:indexPath.row]]];
if (self.delegate) {
      UITapGestureRecognizer* g = [[UITapGestureRecognizer alloc] initWithTarget:self.delegate action:@selector(showPopUpImageView:)];
      [cell.screenImageView addGestureRecognizer:g];
}

return cell;

}

但是，集合视图中显示纵向和横向图像。肖像图像显示得很好，但是在集合视图中景观图像看起来很小。 我需要做的是根据图片大小调整单元格大小以便填充正确的宽高比？

我添加了如下所示的方法，但问题是它在开始时一次调用所有单元格，并且一旦我在cellForRowAtIndexPath方法中下载图像就不会被调用：

    - (CGSize)collectionView:(UICollectionView *)collectionView
              layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

{

return CGSizeMake(165, 255);

}

因此，我想知道如何实现这一功能，如果需要更多信息，请告诉我？

Answer 1

在-setImageWithURLRequest:...中，当图像将其缓存到哈希表中，然后使用当前图像路径调用-reloadItemsAtIndexPaths:时，重新加载单元格，从而导致CollectionView重新检查大小细胞应该是。

确保在查找图像时查阅哈希表。如果collectionView项目在屏幕外滚动并重新打开，这也可以节省额外的网络访问。

注意我担心如果您使用UICollectionReusableView子类，您的代码可能会失败，因为在图像加载之前可以重复使用单元格，因此图像将加载到错误的位置。

Answer 2

但是添加UICollectionView的委托方法。

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UIImageView *image = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[arryOfImg objectAtIndex:indexPath.row]]];

    //You may want to create a divider to scale the size by the way..
    return CGSizeMake((image.frame.size.width)/4.0, (image.frame.size.height)/4.0);
}

根据UICollectionView中的图像动态更改单元格大小

2 个答案: