如何在IOS中以编程方式滚动UICollectionViewCell? [英] How to scroll UICollectionViewCell programmatically in IOS?

问题描述

我有一个垂直的 UICollectionView ，每个单元格都占据了整个 self.view.frame ，我可以轻松地向上滑动以翻页到下一个单元格，但是我想只需按一下按钮即可完成相同的操作.

I have a vertical UICollectionView with each cell taking up the entire self.view.frame I can easily swipe upwards to page to the next cell, but I would like to do the same thing with the press of a button.

我尝试使用:

- (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated

并且:

- (void)scrollRectToVisible:(CGRect)rect animated:(BOOL)animated

它们可以工作，但是它们会暂时变白"当前单元格以显示下一个单元格，而在切换过程中，刷卡会显示两个单元格.

They work but they temporarily "White-Out" the currentCell to present the nextCell, while the swiping shows both cells during the transition.

理想情况下，我想使用:

Ideally I would like to use:

- (void)scrollToItemAtIndexPath:(NSIndexPath *)indexPath atScrollPosition:(UICollectionViewScrollPosition)scrollPosition animated:(BOOL)animated

但是我不知道如何访问nextCell的 indexPath ...我已经尝试过:

But I don't know how to access the nextCell's indexPath... I've tried:

NSIndexPath *nextIndexPath = [_collectionView indexPathForItemAtPoint:CGPointMake(25, (_collectionView.frame.size.height-25)*(_currentIndexRowForCellOnScreen+1))];

其中 _currentIndexRowForCellOnScreen 是 UICollectionView 在屏幕上的首次出现的 indexPath.row :

Where _currentIndexRowForCellOnScreen is the indexPath.row of the UICollectionView's first appearance on screen in:

- (UICollectionViewCell*)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath

但是当我放入它时:

- (NSIndexPath *)indexPathForCell:(UICollectionViewCell *)cell

它在第一个Cell之后返回NULL，并且不设置动画....

it returns NULL after the first Cell, and does not animate....

任何方向将不胜感激.谢谢您的时间.

Any direction would be greatly appreciated. Thank you for your time.

推荐答案

假设您的collectionView仅包含1个部分，并且鉴于每个项目都占据了整个框架，那么您可以执行以下操作；

Assuming your collectionView contains only 1 section, and given that each item occupies the whole frame then you could do something like this;

  NSArray *visibleItems = [self.collectionView indexPathsForVisibleItems];
  NSIndexPath *currentItem = [visibleItems objectAtIndex:0];
  NSIndexPath *nextItem = [NSIndexPath indexPathForItem:currentItem.item + 1 inSection:currentItem.section];
  [self.collectionView scrollToItemAtIndexPath:nextItem atScrollPosition:UICollectionViewScrollPositionTop animated:YES];

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