这与其说是一个问题，不如说是对如何解决这个问题的解释。
首先要意识到的是UICollectionView确实继承自UIScrollView- 因此，使用滚动视图的内容进行标准查找是最好的解决方案。
这是我正在解决的问题：
I had a UICollectionView每个单元格中都有不同的项目 - 以及不同类型的单元格。我需要选择一个单元格以使单元格中的图像看起来扩展并占据整个屏幕。我如何进行扩展是另一篇文章的内容。
挑战在于获取单元格在屏幕上的位置，以便动画部分有一个从哪里开始的参考点。
因此，为了方便获取此信息 - 请考虑以下代码：
第一个注意事项：
UICollectionView *picturesCollectionView;
DrawingCell cell; // -> instanceof UICollectionViewCell with custom items.
// first, get the list of cells that are visible on the screen - you must do this every time
// since the items can change... This is a CRITICAL fact. You do not go through the
// entire list of cells - only those the collectionView indicates are visible. Note
// there are some things to watch out for - the visibles array does not match the indexPath.item
// number - they are independent. The latter is the item number overall the cells, while
// the visibles array may have only 2 entries - so there is NOT a 1-to-1 mapping - keep
// that in mind.
NSArray *visibles = [self.picturesCollectionView visibleCells];
// now, cycle through the times and find the one that matches some criteria. In my
// case, check that the cell for the indexPath passed matches the cell's imageView...
// The indexPath was passed in for the method call - note that the indexPath will point
// to the number in your datasource for the particular item - this is crucial.
for (int i=0; i<visibles.count; i++) {
DrawingCell *cell = (DrawingCell *)visibles[i];
if (cell.imageView.image == (UIImage *)images[indexPath.item]) {
// at this point, we've found the correct cell - now do the translation to determine
// what is it's location on the current screen... You do this by getting the contentOffset
// from the collectionView subtracted from the cell's origin - and adding in (in my case)
// the frame offset for the position of the item I wish to animate (in my case the
// imageView contained within my custom collection cell...
CGFloat relativeX = cell.frame.origin.x - self.picturesCollectionView.contentOffset.x + cell.imageView.frame.origin.x;
CGFloat relativeY = cell.frame.origin.y - self.picturesCollectionView.contentOffset.y + cell.imageView.frame.origin.y;
// I now have the exact screen coordinates of the imageView - so since I need this
// to perform animations, I save it off in a CGRect - in my case, I set the size
// exactly to the size of the imageView - so say you were doing a Flicker display
// where you wanted to grow a selected image, you get the coordinates of the image
// in the cell and the size from the displayed image...
UIImageView *image = cell.imageView;
// selectedCell is a CGRect that's global for the sake of this code...
selectedCell = cell.frame;
selectedCell.origin.x = relativeX;
selectedCell.origin.y = relativeY;
selectedCell.size.width = cell.imageView.frame.size.width;
selectedCell.size.height = cell.imageView.frame.size.height;
}
}
// done. I have my coordinates and the size of the imageView I wish to animate and grow...
希望这可以帮助其他人尝试弄清楚如何在单元格上的精确位置上覆盖某些内容，等等......
-(void)collectionView:(UICollectionView *)cv didSelectItemAtIndexPath:(NSIndexPath *)indexPath;
{
UICollectionViewLayoutAttributes *attributes = [cv layoutAttributesForItemAtIndexPath:indexPath];
CGRect cellRect = attributes.frame;
CGRect cellFrameInSuperview = [cv convertRect:cellRect toView:[cv superview]];
NSLog(@"%f",cellFrameInSuperview.origin.x);
}
这对我有用。你可以自己尝试一下
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