Swift 4 UICollectionView检测滚动结束

Question

我有一个Horizontal UICollectionView在我的应用程序上,我想在用户到达UICollectionView的末尾(或接近结尾)时加载更多数据,同时在左侧拖动.

我正在使用Swift 4.我找到了一些Swift 3解决方案,但它们对我不起作用.

我目前的代码是:

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return self.videoViewModel.images.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CollectionViewCell", for: indexPath) as! CollectionViewCell
    cell.imgImage.image = self.videoViewModel.images[indexPath.row]

    return cell
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    updateVideo(data: self.videoViewModel.relatedVideos[indexPath.row])
}

Answer 1

实现方法scrollViewDidScroll的UIScrollViewDelegate：

var isLoading: Bool = false

 func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let contentOffsetX = scrollView.contentOffset.x
    if contentOffsetX >= (scrollView.contentSize.width - scrollView.bounds.width) - 20 /* Needed offset */ {
        guard !self.isLoading else { return }
        self.isLoading = true
        // load more data
        // than set self.isLoading to false when new data is loaded
    }
}

Answer 2

您可以使用集合视图的cellForItem或willDisplayItem方法.检查是否显示最后一个单元格,然后加载数据.例如:

func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
     if (indexPath.row == dataSource.count - 1 ) { //it's your last cell
       //Load more data & reload your collection view
     }
}