Set collectionView size. (sizeForItemAtIndexPath function is not working) Swift 3

Question

I have a tableView and in every tableViewCell is a collectionView.

I am trying to change the collectionView size with this code:

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

    if collectionView.tag == 2{

        return CGSize(width: 100, height: 100)

    }else if collectionView.tag == 4 {


        return CGSize(width: 222, height: 200)

    }else{


        return CGSize(width: 10, height: 10)
    }

}

The problem is that there is no error but cells do not change sizes

If you need to know something more, just write a comment.

Thank you.

Constringe

Your first statement says you have a tableView, but this looks like a collectionView. Do you have both, or just one? – Waterlog

@Waterlog there is a collection view inside table view cell – Constringe

Answer 1

So This is my code right now and it works:

        collectionView.delegate = dataSourceDelegate
        collectionView.dataSource = dataSourceDelegate
        collectionView.tag = row
        collectionView.setContentOffset(collectionView.contentOffset, animated:false)
        collectionView.reloadData()
        collectionView.register(UINib(nibName: "eventsCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: "eventsCollectionViewCell")


        if row == 2{


            let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
            layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
            layout.itemSize = CGSize(width: 120, height: 120)
            layout.scrollDirection = .horizontal

            collectionView.collectionViewLayout = layout

        }else if row == 4 {


            let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
            layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
            layout.itemSize = CGSize(width: 222, height: 200)
            layout.scrollDirection = .horizontal

            collectionView.collectionViewLayout = layout

        }else{

            print("else")
        }

Constringe

What is row? How and where its declared and assigned? – Duodenum

Answer 2

First, don't forget extends from UICollectionViewDelegateFlowLayout delegate.

For single collectionview display logic :

 func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let width = ((collectionView.frame.width - 15) / 2) // 15 because of paddings
    print("cell width : \(width)")
    return CGSize(width: width, height: 200)
}

And important point in storyboard don't forget Estimate Size : None

Ferryboat

Wow. You saved my day. After changing the Estimate Size from Automatic to None(+ Min Spacing For Cells from 10 to 0 and For Lines from 10 to 0), func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) worked! Before the edit I was experiencing unexpected cell width and min spacing for cells. – Varion

Yes @Varion and I faced same problem. After a long time, I discovered by chance. I'm glad I could help you. – Ferryboat

I am using XCode 11.2.1 and this version has "Automatic" value as default for Estimate Size. So change it to None worked for me. Thanks man! – Tui

Weird XCode additions... right answer for XCode 11.2.1, thanks :) – Mitten

Thanks for the estimated size point... wasted literally half a day on it debugging my size for item – Jerrelljerri

This is also needed if you use xib's as well for your collectionView – Wandawander

UICollectionViewDelegateFlowLayout is the tricky part for me. – Brenza

Yes, it's working. After changing the Estimate Size from Automatic to None. – Sterigma

Answer 3

The signature for this method has changed in Swift 3 to:

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    sizeForItemAt indexPath: IndexPath) -> CGSize {
    // your code here
}

Pay attention to the subtle difference: (_ collectionView: ... instead of (collectionView: ....

This is because in Swift 3, you have to explicitly specify the label of the first parameter. You can override this default behaviour by adding the underscore character _.

Also, make sure that your class adopts both UICollectionViewDelegate and UICollectionViewDelegateFlowLayout protocols

class MyViewController: UICollectionViewDelegateFlowLayout, UICollectionViewDelegate {

    // your code here

    func collectionView(_ collectionView: UICollectionView,
                layout collectionViewLayout: UICollectionViewLayout,
                sizeForItemAt indexPath: IndexPath) -> CGSize {
        // your code here
    }
}

Refer to this link to learn more about changes in Swift 3.

Frizzy

I have updated my code but it does not change the cell size :/ – Constringe

add "UICollectionViewDelegateFlowLayout" in delgate call – Wilen

This is the right answer. Thank you so much for this! UICollectionViewDelegateFlowLayout is key – Heddy

@BaljeetSingh what do you mean by "add "UICollectionViewDelegateFlowLayout" in delgate call"? – Madelenemadelin

@Madelenemadelin let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout() layout.sectionInset = UIEdgeInsets(top: -1, left: -1, bottom: -1, right: -1) let value:CGFloat = (UIScreen.main.bounds.width)/2; layout.itemSize = CGSize(width: value, height: value) layout.minimumInteritemSpacing = 0 layout.minimumLineSpacing = 0 GridView!.collectionViewLayout = layout – Wilen

for me it was UICollectionViewDelegateFlowLayout, previous developer didn't add that. – Dogface

Answer 4

You need to specify that you implement the protocol UICollectionViewDelegateFlowLayout in your class declaration.

class PhrasesCompactCollectionViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout

Schach

Answer 5

Short Version:

Try adding

collectionView.delegate = dataSource

Longer version:

For Me this was a small mistake -

collectionView.dataSource = self

This would call these methods

func numberOfSections(in collectionView: UICollectionView) -> Int
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell

However it would NOT call

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

Because this is not part of UICollectionView 's dataSource. It's part of UICollectionView's delegate.

So adding the following solved my issue.

collectionView.delegate = dataSource

Vaseline

Why are you setting collectionView.delegate = dataSource instead of collectionView.delegate = self – Instill

Answer 6

I've had the same problem! If you make the size half the width (width/2), then it will still appear like the entire width because the padding is being added to the width/2.

Fix: Make sure to set the section insets in Storyboard to 0. Alternatively, adjust the width/2 to a size that INCLUDES the section insets.

It took me a while to fix that one ;-)

Indecent

Answer 7

Don't forget to assign UICollectionViewFlowLayout object to your collectionViewLayout since UICollectionView uses UICollectionViewLayout (not UICollectionViewFlowLayout) by default.

let flowLayout = UICollectionViewFlowLayout()

collectionView.collectionViewLayout = flowLayout

Knocker