How to adjust height of UICollectionView to be the height of the content size of the UICollectionView?

Question

I would like the UICollectionView (The red one) to shrink to the height of the content size in this case UICollectionViewCells(the yellow ones) because there is a lot of empty space. What I tried is to use:

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

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

but return self.collection.contentSize always return (width, 0) and for this reason it shrinks too much to value of height 30 (The value which I set in the XIB file for the height, although I have constaint >= 30).

Answer 1

I would suggest the following:

1. Add a height constraint to your collection view.
2. Set its priority to 999.
3. Set its constant to any value that makes it reasonably visible on the storyboard.
4. Change the bottom equal constraint of the collection view to greater or equal.
5. Connect the height constraint to an outlet.
6. Every time you reload the data on the collection view do the following:

You may also want to consider the Inset of the collection view by adding it to the content size.

Code Sample:

CGFloat height = myCollectionView.collectionViewLayout.collectionViewContentSize.height
heightConstraint.constant = height
self.view.setNeedsLayout() Or self.view.layoutIfNeeded()

Explanation: Extra, You don't have to read if you understand it. obviously!!

The UI will try to reflect all the constraints no matter what are their priorities. Since there is a height constraint with lower priority of (999), and a bottom constraint of type greater or equal. whenever, the height constraint constant is set to a value less than the parent view height the collection view will be equal to the given height, achieving both constraints.

But, when the height constraint constant set to a value more than the parent view height both constraints can't be achieved. Therefore, only the constraint with the higher priority will be achieved which is the greater or equal bottom constraint.

The following is just a guess from an experience. So, it achieves one constrant. But, it also tries to make the error in the resulted UI for the other un-achieved lower priority constraint as lowest as possible. Therefore, the collection view height will be equal to the parent view size.

Answer 2

1) Set Fix Height of your CollectionView.

2) Create Outlet of this CollectionView Height Constant. Like :

IBOutlet NSLayoutConstraint *constHeight;

3) Add below method in your .m file:

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

    CGFloat height = collectionMenu.collectionViewLayout.collectionViewContentSize.height;
    constHeight.constant = height;
}

Answer 3

I ended up, by subclassing the UICollectionView and overriding some methods as follows.

• Returning self.collectionViewLayout.collectionViewContentSize for intrinsicContentSize makes sure, to always have the correct size
• Then just call it whenever it might change (like on reloadData)

Code:

override func reloadData() {
    super.reloadData()
    self.invalidateIntrinsicContentSize()
}

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

But be aware, that you lose "cell re-using", if you display large sets of data, eventhough they don't fit on the screen.

Answer 4

In Swift 5 and Xcode 10.2.1

1. Fix Height of the CollectionView

2. Create Outlet of your CollectionViewHeight

   IBOutlet weak var myCollectionViewHeight: NSLayoutConstraint!
   

3. Use below code

   override func viewDidLayoutSubviews() {
       super.viewDidLayoutSubviews()
       let height = myCollectionView.collectionViewLayout.collectionViewContentSize.height
       myCollectionViewHeight.constant = height
       self.view.layoutIfNeeded()
   }
   

Answer 5

You have to set height constraint as equal to content size

HeightConstraint.constant = collection.contentSize.height 

Answer 6

This seemed like the simplest solution for me.

class SelfSizingCollectionView: UICollectionView {
    override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
        super.init(frame: frame, collectionViewLayout: layout)
        commonInit()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }

    private func commonInit() {
        isScrollEnabled = false
    }

    override var contentSize: CGSize {
        didSet {
            invalidateIntrinsicContentSize()
        }
    }

    override func reloadData() {
        super.reloadData()
        self.invalidateIntrinsicContentSize()
    }

    override var intrinsicContentSize: CGSize {
        return contentSize
    }
}

You may not need to override reloadData

Answer 7

Took the solution by d4Rk which is great, except in my case it would keep cutting off the bottom of my collection view (too short). I figured out this was because intrinsic content size was sometimes 0 and this would throw off the calculations. IDK. All I know is this fixed it.

import UIKit

class SelfSizedCollectionView: UICollectionView {
    override func reloadData() {
        super.reloadData()
        self.invalidateIntrinsicContentSize()
    }

    override var intrinsicContentSize: CGSize {
        let s = self.collectionViewLayout.collectionViewContentSize
        return CGSize(width: max(s.width, 1), height: max(s.height,1))
    }

}

Answer 8

Do following.

1. first set height constrain for UICollectionView
2. here calendarBaseViewHeight is UICollectionView height Variable

3. call the function after reload the collection view

   func resizeCollectionViewSize(){  
          calendarBaseViewHeight.constant = collectionView.contentSize.height      
    }
   

Answer 9

1. Subclass UICollectionView as follows
2. Delete height constraint if any
3. Turn on Intrinsic Size

-

class ContentSizedCollectionView: UICollectionView {
    override var contentSize:CGSize {
        didSet {
            invalidateIntrinsicContentSize()
        }
    }

    override var intrinsicContentSize: CGSize {
        layoutIfNeeded()            
        return CGSize(width: UIView.noIntrinsicMetric, height: collectionViewLayout.collectionViewContentSize.height)
    }
}

Answer 10

first of all calculate number of cells than multiply it with height of cell and then return height in this method

    collectionView.frame = CGRectMake (x,y,w,collectionView.collectionViewLayout.collectionViewContentSize.height); //objective c
    //[collectionView reloadData];
   collectionView.frame = CGRect(x: 0, y: 0, width: width, height: collectionView.collectionViewLayout.collectionViewContentSize.height) // swift

Answer 11

On your UICollectionView set your constraints such as Trailing, Leading, and Bottom:

If you look at my height constraint in more detail, as it is purely for storyboard look so I don't get errors, I have it to Remove at build time. The real height constraint is set in my code down below.

My code for DrawerCollectionView, which is set as the collection view Custom Class:

import UIKit

class DrawerCollectionView: UICollectionView {

    override func didMoveToSuperview() {
        super.didMoveToSuperview()

        heightAnchor.constraint(equalToConstant: contentSize.height).isActive = true
    }
}

Answer 12

work for me

    let heightRes = resCollectionView.collectionViewLayout.collectionViewContentSize.height
    foodHeightConstrant.constant = height.advanced(by: 1 )

    foodCollectionView.setNeedsLayout()
    foodCollectionView.layoutIfNeeded()

Answer 13

If you set the height constraint of the collection view. Just observe the contentSize change in the viewDidLoad and update the constraint.

        self.contentSizeObservation = collectionView.observe(\.contentSize, options: [.initial, .new]) { [weak self] collectionView, change in
            guard let `self` = self else { return }
            guard self.collectionView.contentSize != .zero else { return }
            self.collectionViewHeightLayoutConstraint.constant = self.collectionView.contentSize.height
        }

Answer 14

I have a multi-line, multi-selection UICollectionView subclass where the cells are of fixed height and left-aligned flowing from left to right. It's embedded in a vertical stack view that's inside a vertical scroll view. See the UI component below the label "Property Types".

In order for the collection view to fit the height of its contentSize, here's what I had to do (note that this is all within the UICollectionView subclass):

1. Give the collection view a non-zero minimum height constraint of priority 999. Auto-sizing the collection view to its content height simply won't work with zero height.

   let minimumHeight = heightAnchor.constraint(greaterThanOrEqualToConstant: 1)
   minimumHeight.priority = UILayoutPriority(999)
   minimumHeight.isActive = true
   

2. Set the collection view's content hugging priority to .required for the vertical axis.

   setContentHuggingPriority(.required, for: .vertical)
   

3. Calling reloadData() is followed by the following calls:

   invalidateIntrinsicContentSize()
   setNeedsLayout()
   layoutIfNeeded()
   

   For example, I have a setItems() function in my subclass:

   func setItems(_ items: [Item]) {
     self.items = items
     selectedIndices = []
     reloadData()
     invalidateIntrinsicContentSize()
     setNeedsLayout()
     layoutIfNeeded()
   }
   

4. Override contentSize and intrinsicContentSize as follows:

   override var intrinsicContentSize: CGSize {
     return contentSize
   }
   
   override var contentSize: CGSize {
     didSet {
       invalidateIntrinsicContentSize()
       setNeedsLayout()
       layoutIfNeeded()
     }
   }
   

Answer 15

Adjusting height of UICollectionView to the height of it's content size 🙌🏻

SWIFT 5

final class MyViewController: UIViewController {

    // it's important to declare layout as separate constant due to late update in viewDidLayoutSubviews()
    private let layout = UICollectionViewFlowLayout()
    private lazy var collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)


    override func viewDidLoad() {
        super.viewDidLoad()
    
        setupCollectionView()
        setupCollectionViewConstraints()
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
    
        updateFlowLayout()
    }

    private func setupCollectionView() {
        view.addSubview(collectionView)
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "UICollectionViewCell")
        collectionView.dataSource = self
    }

    private func setupCollectionViewConstraints() {
        // your collectionView constraints setup
    }

    private func updateFlowLayout() {
        let height = collectionView.collectionViewLayout.collectionViewContentSize.height
        layout.itemSize = CGSize(width: view.frame.width, height: height)
        layout.scrollDirection = .horizontal
        layout.minimumInteritemSpacing = .zero
        layout.minimumLineSpacing = .zero
        layout.sectionInset = UIEdgeInsets.zero
    }
}

extension MyViewController: UICollectionViewDataSource {
     func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {...}
     func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {...}
}

Answer 16

Get the height of the cell. Something like this

let cellHeight = cell.frame.height

Get the origin of the collection view

let cvOrigin = collectionView.frame.origin

Get the width of the collection view

let cvWidth = collectionView.bounds.width

Set the frame of the content view

collection.frame = CGRect(x: cvOrigin.x, y: cvOrigin.y, width: cvWidth, height: cellHeight )