Swift - Center Horizontally UICollectionView Cell doesn't work

Question

this is the code in the ViewController for CollectionView but it doesn't make Cells to be in the center of CollectionView and here's the result:

extension DeviceAndEquipmentViewController : UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 1
}

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    if collectionView === deviceCollectionView {
        guard selectedDeviceList.count != 0 else {
            selectedDeviceList.insert("nil", at: 0)
            return 1
        }
        return selectedDeviceList.count
    } else if collectionView === equipmentCollectionView {
        guard selectedEquipmentList.count != 0 else {
            selectedEquipmentList.insert("nil", at: 0)
            return 1
        }
        return selectedEquipmentList.count
    } else if collectionView === softwareCollectionView {
        guard selectedSoftwareList.count != 0 else {
            selectedSoftwareList.insert("nil", at: 0)
            return 1
        }
        return selectedSoftwareList.count
    } else {
        return 0
    }

}


func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {

    let inset:CGFloat = 10
    return UIEdgeInsets(top: inset, left: inset, bottom: inset, right: inset)

}

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

                let numberOfItemsPerRow:CGFloat = 1
                 let spacingBetweenCells:CGFloat = 16

                let totalSpacing = (2 * self.spacing) + ((numberOfItemsPerRow - 1) * spacingBetweenCells)

                let width = (deviceCollectionView.bounds.width - totalSpacing) / numberOfItemsPerRow

    if collectionView == deviceCollectionView {

            let device = self.selectedDeviceList[indexPath.row]

            if device != "nil" {
                    return CGSize(width: width, height: 45)
            } else {
                    return CGSize(width: width + 15, height: 55)
        }
    } else if collectionView == equipmentCollectionView {

            let equipment = self.selectedEquipmentList[indexPath.row]
            if equipment != "nil" {
                return CGSize(width: width, height: 45)
            } else {
                return CGSize(width: width + 15, height: 55)
        }
    } else {

        let software = self.selectedSoftwareList[indexPath.row]

            if software != "nil" {
                return CGSize(width: width, height: 45)
            } else {
                return CGSize(width: width + 15, height: 55)
        }
    }


}
}

and here's the setup for each CollectionView FlowLayout

let layout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: spacing, left: spacing, bottom: spacing, right: spacing)
    layout.minimumLineSpacing = spacing
    layout.minimumInteritemSpacing = spacing
    self.equipmentCollectionView?.collectionViewLayout = layout

I've seen the other topics, but it didn't fix my problem, I use XIB for each collection view cell and didn't do all in Code, I appreciate if you help me figure this out.

@AqeelAhmad yes I applied an anchor for all the views to the safe area — Arash Afsharpour, Jan 02 '20 at 14:21
@AqeelAhmad depends on items per row, the spacing variable is equal 16 — Arash Afsharpour, Jan 02 '20 at 14:45
I think you are doing something wrong with the calculation of the width. try to apply a hard code value instead of calculations. By doing this you will be able to know that either you are doing wrong calculations or problem is something else. — Aqeel Ahmad, Jan 02 '20 at 14:49
Problem is this exact code is working in another viewcontroller and CollectionView cell, I've been working on this for 3 days, still no clue where's the problem @AqeelAhmad — Arash Afsharpour, Jan 02 '20 at 14:55
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/205237/discussion-between-arash-afsharpour-and-aqeel-ahmad). — Arash Afsharpour, Jan 02 '20 at 14:58

score 0 · Accepted Answer · answered Jan 02 '20 at 20:21

I found the answer but Still I don't know what is wrong with it that it work in other ViewController but not this one, the only difference between this ViewController and others is that in this one I used more than 1 ViewController. I linked the answer below, so if anyone has this issue can fix it, I used the Second solution and it worked. thanks to Cœur for sharing this.

Answer

Swift - Center Horizontally UICollectionView Cell doesn't work

1 Answers1