How to determine height of UICollectionView with F

Question

I've got an UICollectionView with an UICollectionViewFlowLayout, and i want to calculate its content size (for return in intrinsicContentSize needed for adjusting its height via AutoLayout).

The problems is: Even if I have a fixed and equal height for all cells, I don't know how many "rows"/lines I have in the UICollectionView. I also can't determine that count by the number of items in my data source, since the cells representing the data items vary in width, so does consequently the number of items I have in one line of the UICollectionView.

Since I couldn't find any hints on this topic in the official documentation and googling didn't bring me any further, any help and ideas would be appreciated very much.

Answer 1

Whoa! For some reason, after hours of research, I now found a pretty easy answer to my question: I was completely searching in the wrong place, digging through all the documentation I could find on UICollectionView.

The simple and easy solution lies in the underlying layout: Just call collectionViewContentSize on your myCollectionView.collectionViewLayout property and you get the height and width of the content as CGSize. It's as easy as that.

Answer 2

It's too late to answer this question but I have recently gone through this issue.
@lee's above answer help me a lot to get my answer. But that answer is limited to objective-c and I was working in swift.
@lee With reference to your answer, allow me to let the swift user get this issue solved easily. For that, please follow below steps:

Declare a CGFloat variable in declaration section:

var height : CGFloat!

At viewDidAppear you can get it by:

height = self.myCollectionView.collectionViewLayout.collectionViewContentSize().height

Maybe when you reload data then need to calculate a new height with new data then you can get it by: addObserver to listen when your CollectionView finished reload data at viewWillAppear:

override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(true)
        ....
        ....
        self.shapeCollectionView.addObserver(self, forKeyPath: "contentSize", options: NSKeyValueObservingOptions.Old, context: nil)
    }

Then add bellow function to get new height or do anything after collectionview finished reload:

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        let newHeight : CGFloat = self.myCollectionView.collectionViewLayout.collectionViewContentSize().height

        var frame : CGRect! = self.myCollectionView.frame
        frame.size.height = newHeight

        self.myCollectionView.frame = frame
    }

And don't forget to remove observer:

override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(true)
    ....
    ....
    self.myCollectionView.removeObserver(self, forKeyPath: "contentSize")
}

I hope this will help you to solve your issue in swift.

Answer 3

Swift 4

class DynamicCollectionView: UICollectionView {
  override func layoutSubviews() {
    super.layoutSubviews()
    if !__CGSizeEqualToSize(bounds.size, self.intrinsicContentSize) {
      self.invalidateIntrinsicContentSize()
    }
  }

  override var intrinsicContentSize: CGSize {
    return collectionViewLayout.collectionViewContentSize
  }
}