检查单元格是否完全显示在集合视图中 [英] Check if cell completely displayed in collectionview

问题描述

我有一个集合视图，其中单元格的大小与集合视图完全相同，因此每个单元格都应占据整个屏幕.我已经实现了一个功能，当它在滚动中拖动或减速时，单元格会被捕捉到完整的视图.这就是用户体验的工作方式.

I have a collection view where the cell is of the size exactly to the collectionView, so each cell should occupy the whole screen. I have implemented a functionality where the cell is snapped to the complete view whenever it's dragged or decelerated through the scroll. This is how the UX works.

https://drive.google.com/open?id=1v8-WxCQUzfu8V_k9zM1UCWsf_-Zz4dpr

我想要的:

正如您从剪辑中看到的，单元格对齐整个屏幕.现在，我想在它捕捉后执行一个方法.在部分显示之前或之前不显示.

As you can see from the clip, the cell snaps to the whole screen. Now, I want to execute a method after it snaps. Not before or not when it's partially displayed.

以下是我为捕捉效果编写的代码:

Following is the code I have written for snapping effect :

func scrollToMostVisibleCell(){
    let visibleRect = CGRect(origin: collectionView.contentOffset, size: collectionView.bounds.size)
    let visiblePoint = CGPoint(x: visibleRect.midX, y: visibleRect.midY)
    let visibleIndexPath = collectionView.indexPathForItem(at: visiblePoint)!
    collectionView.scrollToItem(at: visibleIndexPath as IndexPath, at: .top, animated: true)
    print("cell is ---> ", visibleIndexPath.row)
}



func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    scrollToMostVisibleCell()
}

func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    scrollToMostVisibleCell()
    if !decelerate {
        scrollToMostVisibleCell()
    }
}

如果我使用 willDisplayCell 方法，那么只要单元格在视图中，它就会立即返回我，即使它只是在 collectionView 中偷看.

If I use willDisplayCell method, then it' just going to return me as soon as the cell is in the view, even if it's just peeping in the collectionView.

有没有办法检查单元格是否完全在视图中，然后我可以执行某个功能?

我已经为这个问题在互联网上报废了，但找不到满意的答案.

I have scrapped the internet over this question, but ain't able to find a satisfactory answer.

推荐答案

使用 followedCollectionView.indexPathsForVisibleItems() 获取可见单元格 visibleIndexPaths 并检查您的 indexPath<在对单元格执行任何操作之前，/code> 是否包含在 visibleIndexPaths 中.参考:@anhtu 检查 indexPath 处的单元格是否可见屏幕 UICollectionView

Using followedCollectionView.indexPathsForVisibleItems() to get visible cells visibleIndexPaths and check your indexPath is contained in visibleIndexPaths or not, before doing anything with cells. Ref : @anhtu Check whether cell at indexPath is visible on screen UICollectionView

同样来自 Apple :var visibleCells: [UICollectionViewCell] { get } .返回集合视图当前显示的可见单元格数组.

Also from Apple : var visibleCells: [UICollectionViewCell] { get } . Returns an array of visible cells currently displayed by the collection view.

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