How to determine height of UICollectionView with FlowLayout

Question

I\'ve got an UICollectionView with an UICollectionViewFlowLayout, and i want to calculate its content size (for return in intrinsicContentSiz

Answer 1

In addition，you'd better calling reloadData before getting the height:

theCollectionView.collectionViewLayout.collectionViewContentSize;

Answer 2

Swift version of @user1046037:

public class DynamicCollectionView: UICollectionView {

    override public func layoutSubviews() {
        super.layoutSubviews()
        if !bounds.size.equalTo(intrinsicContentSize) {
            invalidateIntrinsicContentSize()
        }
    }

    override public var intrinsicContentSize: CGSize {
        let intrinsicContentSize: CGSize = contentSize
        return intrinsicContentSize
    }
}

Answer 3

At viewDidAppear you can get it by:

float 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: add observer to listen when your CollectionView finished reload data at viewdidload:

[self.myCollectionView addObserver:self forKeyPath:@"contentSize" options:NSKeyValueObservingOptionOld context:NULL];

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

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary  *)change context:(void *)context
{
    //Whatever you do here when the reloadData finished
    float newHeight = self.myCollectionView.collectionViewLayout.collectionViewContentSize.height;    
}

And don't forget to remove observer:

[self.myCollectionView removeObserver:self forKeyPath:@"contentSize" context:NULL];

Answer 4

Swift 4.2

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

    override var intrinsicContentSize: CGSize {
        return self.contentSize
    }
}

Answer 5

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 6

Swift 4.2, Xcode 10.1, iOS 12.1:

For some reason, collectionView.contentSize.height was appearing smaller than the resolved height of my collection view. First, I was using an auto-layout constraint relative to 1/2 of the superview's height. To fix this, I changed the constraint to be relative to the "safe area" of the view.

This allowed me to set the cell height to fill my collection view using collectionView.contentSize.height:

private func setCellSize() {
    let height: CGFloat = (collectionView.contentSize.height) / CGFloat(numberOfRows)
    let width: CGFloat = view.frame.width - CGFloat(horizontalCellMargin * 2)

    let layout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
    layout.itemSize = CGSize(width: width, height: height)
}

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