Get number of rows in UICollectionView - ios

Question

UICollection view automatically adjusts the number of rows based on the number of items per section and size of each cell.
So is there a way to get the number of rows in an UICollectionView?
For example: If I have a calendar with 31 days that automatically fit into n rows.
How do I get the value of this 'n' ?

Answer 1

You can get the position of an item after it's laid out with [myCollectionView.collectionViewLayout layoutAttributesForItemAtIndexPath:]
If you don't know the dimensions of your items, or don't want to assume that you do, one approach would be to iterate over the items in your collection and look for a step change in the Y-position of the item. Obviously this only works if you're using a grid-based layout.
This does the trick:
NSInteger totalItems = [myCollectionView numberOfItemsInSection:0];
// How many items are there per row?
NSInteger currItem;
CGFloat currRowOriginY = CGFLOAT_MAX;
for (currItem = 0; currItem < totalItems; currItem++) {
UICollectionViewLayoutAttributes *attributes =
[collectionView.collectionViewLayout layoutAttributesForItemAtIndexPath:
[NSIndexPath indexPathForItem:currItem inSection:0]];
if (currItem == 0) {
currRowOriginY = attributes.frame.origin.y;
continue;
}
if (attributes.frame.origin.y > currRowOriginY + 5.0f) {
break;
}
}
NSLog(#"new row started at item %ld", (long)currItem);
NSInteger totalRows = totalItems / currItem;
NSLog(#"%ld rows", (long)totalRows);
If you do know the dimensions of your items, you could get the position of the last item with
NSInteger totalItems = [self.timelineCollectionView numberOfItemsInSection:0];
NSIndexPath lastIndex = [NSIndexPath indexPathForItem:totalItems - 1 inSection:0];
UICollectionViewLayoutAttributes *attributes =
[myCollectionView.collectionViewLayout layoutAttributesForItemAtIndexPath:lastIndex];
// Frame of last item is now in attributes.frame
Then take that last item's dimensions and divide by your known row height. Don't forget to account for any headers or spacing. These properties are also available from the UICollectionViewFlowLayout.
Pull the flow layout out with
UICollectionViewFlowLayout *myFlowLayout = (UICollectionViewFlowLayout*)myCollectionView.collectionViewFlowLayout;
And look in
myFlowLayout.headerReferenceSize
myFlowLayout.minimumLineSpacing
and so on.