UICollectionView challenge: set height on the last cell to fit availabe space - ios

Question

Can you solve the following problem: I have a UICollectionView with a fixed number of CollectionView Cells - but the hight of the devices change and I have to dynamically calculate the last(buttom) cell.
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I: Cell 1
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I: Cell 2
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I: Cell 3, This cell has a dynamic hight
I
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I have tried the following:
note: let view = self.cells[indexPath.row] is a fixed list of UIView that I add to the UICollectionView contextView in cellForItemAt
Also the code is in a class that implement UICollectionViewDelegateFlowLayout
self.collectionView?.isScrollEnabled = false
var totalHight: CGFloat = 0
public func collectionView(_ collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAt indexPath: IndexPath) -> CGSize {
let view = self.cells[indexPath.row]
self.totalHight = self.totalHight + view.frame.size.height
if (self.totalHight > self.frame.size.height){
let diff = self.totalHight - self.frame.size.height
let height = (view.frame.size.height - diff)
view.frame.size = CGSize(width: self.frame.size.width,
height: height)
self.totalHight = 0
return view.frame.size
}else{
return CGSize(width: self.frame.size.width, height: view.frame.size.height)
}
}

Answer 1

I can't tell if that code you've tried is in your view controller or a custom layout. What was the result?
This can be done with a custom UICollectionViewLayout instance. You can probably get by with subclassing UICollectionViewFlowLayout and overriding
collectionView:layout:sizeForItemAtIndexPath:
Then you can look at the remaining space on the screen. It will probably pose problems if the content ends up exceeding the available space.
One approach you might look at is getting the layout attributes for the previous cell, and that will give you its frame, something like this:
let previousIndexPath = IndexPath(row: indexPath.row - 1, section: indexPath.section)
let attribs = layoutAttributesForItem(at: previousIndexPath)
let previousFrame = attribs.frame
let availableHeight = totalHeight - previousFrame.size.height
return CGSize(width: previousFrame.width, height: availableHeight)
See more here:
https://developer.apple.com/library/content/documentation/WindowsViews/Conceptual/CollectionViewPGforIOS/UsingtheFlowLayout/UsingtheFlowLayout.html
https://developer.apple.com/documentation/uikit/uicollectionviewlayout/1617797-layoutattributesforitem
Edit: as an aside, it sounds like maybe using UIStackView and autolayout constraints would make this thing much easier, since your content is static and doesn't scroll.