How to change UICollectionViewCell size programmatically in Swift?

Question

I have a UICollectionView with a segmented control to switch between data. But how do I change the UICollectionViewCell size properties programmatically ? then I can custom each style appropriately for each data type.

For example change the width to 520 points and height to 100. I am new to iOS development and am experienced with CSS :/

I know how to do it in Xcode (obviously) but do not know the correct methods to change it in swift. Any ideas or feedback is much appreciated (Y)

Answer 1

Make sure you conform to UICollectionViewDelegateFlowLayout for your class (for swift4)

eg. class MyClass: UICollectionViewDelegateFlowLayout

Prior to Swift 3

//Use for size
func collectionView(collectionView: UICollectionView,
        layout collectionViewLayout: UICollectionViewLayout,
        sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {

    }
//Use for interspacing
    func collectionView(collectionView: UICollectionView,
        layout collectionViewLayout: UICollectionViewLayout,
        minimumInteritemSpacingForSectionAtIndex section: Int) -> CGFloat {
            return 1.0
    }

    func collectionView(collectionView: UICollectionView, layout
        collectionViewLayout: UICollectionViewLayout,
        minimumLineSpacingForSectionAtIndex section: Int) -> CGFloat {
            return 1.0
    }

// For swift 3

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    sizeForItemAt indexPath: IndexPath) -> CGSize {

}

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
    return 1.0
}

func collectionView(_ collectionView: UICollectionView, layout
    collectionViewLayout: UICollectionViewLayout,
                    minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return 1.0
}

// For swift 4

extension MyClass: UICollectionViewDelegateFlowLayout { 
        func collectionView(_ collectionView: UICollectionView,
                            layout collectionViewLayout: UICollectionViewLayout,
                            sizeForItemAt indexPath: IndexPath) -> CGSize {

        }

        func collectionView(_ collectionView: UICollectionView,
                            layout collectionViewLayout: UICollectionViewLayout,
                            minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
            return 1.0
        }

        func collectionView(_ collectionView: UICollectionView, layout
            collectionViewLayout: UICollectionViewLayout,
                            minimumLineSpacingForSectionAt section: Int) -> CGFloat {
            return 1.0
        }
    }

use the same code as shown above for swift 3 but just make sure your class conforms to protocol UICollectionViewDelegateFlowLayout

Answer 2

Swift 3

Methods from @sumit-oberoi answer won't be called if you are using Swift 3. To make it work make this adjustments:

1. Conform to the UICollectionViewDelegateFlowLayout protocol.

2. Implement these methods:

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize { } func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat { return 1.0 } func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat { return 1.0 }

Notice the changes:

1. add _ before collectionView in the method name
2. NSIndexPath changes to IndexPath

Answer 3

Swift 3

override func viewDidLoad() {
    super.viewDidLoad()

    let cellSize = CGSize(width:80 , height:80)

    let layout = UICollectionViewFlowLayout()
    layout.scrollDirection = .vertical //.horizontal
    layout.itemSize = cellSize
    layout.sectionInset = UIEdgeInsets(top: 1, left: 1, bottom: 1, right: 1)
    layout.minimumLineSpacing = 1.0
    layout.minimumInteritemSpacing = 1.0
    myCollectionView.setCollectionViewLayout(layout, animated: true)

    myCollectionView.reloadData()
}

Answer 4

if you use Gaurav Rami's code bellow

let cellSize = CGSize(width:80 , height:80)

let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .vertical //.horizontal
layout.itemSize = cellSize
layout.sectionInset = UIEdgeInsets(top: 1, left: 1, bottom: 1, right: 1)
layout.minimumLineSpacing = 1.0
layout.minimumInteritemSpacing = 1.0
myCollectionView.setCollectionViewLayout(layout, animated: true)

and get this message " Snapshotting a view that has not been rendered results in an empty snapshot. Ensure your view has been rendered at least once before snapshotting or snapshot after screen updates. " you should remove animated when setting view layout for collection view

myCollectionView.setCollectionViewLayout(layout, animated: false)

then the message will disappear

Answer 5

Try to use UICollectionViewDelegateFlowLayout method. In Xcode 11 or later, you need to set Estimate Size to none from storyboard.

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: 
UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
  let padding: CGFloat =  170
  let collectionViewSize = advertCollectionView.frame.size.width - padding
  return CGSize(width: collectionViewSize/2, height: collectionViewSize/2)
}

Answer 6

1. In Storyboard Select the Collection View and Set Estimate Size property as NONE in Size Inspector like this:

2. In View Controller add the UICollectionViewDelegateFlowLayout for View Controller

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let itemsPerRow:CGFloat = 2
    let padding:CGFloat = 20
    let itemWidth = (collectionView.bounds.width / itemsPerRow) - padding:CGFloat
    let itemHeight = collectionView.bounds.height - (2 * padding:CGFloat)
    return CGSize(width: itemWidth, height: itemHeight)
}

Answer 7

Swift 5:

1. Conform to the UICollectionViewDelegateFlowLayout protocol, it means you need to put that protocol in the inheritances of your class or as a extension. Like this:

    class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout { }

2. Implement the sizeForItemAt method:

   func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize { return CGSize(width: 100, height: 100) }

You can put the width and height you want in the CGSize constructor.

Answer 8

     /// this method is used for flow layout
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let numberOfItemsPerRow:CGFloat = 3
    let spacingBetweenCells:CGFloat = 2

    // 2 is the value of sectionInset value
    
    let totalSpacing = (2 * 2) + ((numberOfItemsPerRow - 1) * spacingBetweenCells) //Amount of total spacing in a row
    if let collection = self.collectionAccounts{
        let width = (collection.bounds.width - totalSpacing)/numberOfItemsPerRow
        
        return CGSize(width: width, height: width)
    }else{
        return CGSize(width: 0, height: 0)
    }
}

Answer 9

first Conform protocol the UICollectionViewDelegateFlowLayout

set width and height  UICollectionViewCell 

UIcollectionViewCell Hight = 300;
UIcollectionViewCell Width = 380;

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout,sizeForItemAt indexPath: IndexPath) -> CGSize {
      return CGSize(width: CGFloat((380)), height: CGFloat(300))
    }