How to determine height of UICollectionView with FlowLayout

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.

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  • 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.

    6 Solutions Collect From Internet About “How to determine height of UICollectionView with FlowLayout”

    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.

    In case you are using Auto layout, then you could create a subclass of UICollectionView

    If you use the below the code then you don’t have to specify any height constraints for the collection view as it would vary based on the contents of the collection view.

    Given below is the implementation:

    @interface DynamicCollectionView : UICollectionView
    
    @end
    
    @implementation DynamicCollectionView
    
    - (void) layoutSubviews
    {
        [super layoutSubviews];
    
        if (!CGSizeEqualToSize(self.bounds.size, [self intrinsicContentSize]))
        {
            [self invalidateIntrinsicContentSize];
        }
    }
    
    - (CGSize)intrinsicContentSize
    {
        CGSize intrinsicContentSize = self.contentSize;
    
        return intrinsicContentSize;
    }
    
    @end
    

    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];
    

    user1046037 answer in Swift…

    class DynamicCollectionView: UICollectionView {
        override func layoutSubviews() {
            super.layoutSubviews()
            if bounds.size != intrinsicContentSize() {
                invalidateIntrinsicContentSize()
            }
        }
    
        override func intrinsicContentSize() -> CGSize {
            return self.contentSize
        }
    }
    

    Swift 3 code for user1046037 answer

    import UIKit
    
    class DynamicCollectionView: UICollectionView {
    
        override func layoutSubviews() {
            super.layoutSubviews()
            if !__CGSizeEqualToSize(bounds.size, self.intrinsicContentSize) {
                self.invalidateIntrinsicContentSize()
            }
    
        }
    
        override var intrinsicContentSize: CGSize {
            return contentSize
        }
    
    }
    

    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:

    self.myCollectionView.removeObserver(self, forKeyPath: "contentSize")
    

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