How to set cell spacing and UICollectionView - UICollectionViewFlowLayout size ratio?

Swift Uicollectionview Uicollectionviewcell Uicollectionviewlayout

Swift Problem Overview

I'm trying to add UICollectionView to ViewController, and I need to have 3 cells 'per row' without blank space between cells (it should look like a grid). Cell width should be one third of screen size, so I thought that the layout.item width should be the same. But then I get this:

layout.itemSize width = screenSize.width/3

If I reduce that size (by 7 or 8 pixels e.g.), it's better, but the third cell in row is not completely visible, and I still have that blank space (top & bottom, and left & right) .

enter image description here

class ViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
    var collectionView: UICollectionView?
    var screenSize: CGRect!
    var screenWidth: CGFloat!
    var screenHeight: CGFloat!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        screenSize = UIScreen.mainScreen().bounds
        screenWidth = screenSize.width
        screenHeight = screenSize.height
        
        // Do any additional setup after loading the view, typically from a nib
        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 20, left: 0, bottom: 10, right: 0)
        layout.itemSize = CGSize(width: screenWidth / 3, height: screenWidth / 3)
        collectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
        collectionView!.dataSource = self
        collectionView!.delegate = self
        collectionView!.registerClass(CollectionViewCell.self, forCellWithReuseIdentifier: "CollectionViewCell")
        collectionView!.backgroundColor = UIColor.greenColor()
        self.view.addSubview(collectionView!)
    }

    func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
        return 1
    }
    
    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 20
    }
    
    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("CollectionViewCell", forIndexPath: indexPath) as CollectionViewCell
        cell.backgroundColor = UIColor.whiteColor()
        cell.layer.borderColor = UIColor.blackColor().CGColor
        cell.layer.borderWidth = 0.5
        cell.frame.size.width = screenWidth / 3
        cell.frame.size.height = screenWidth / 3
        
        cell.textLabel?.text = "\(indexPath.section):\(indexPath.row)"
        return cell
    }
}

Swift Solutions

Solution 1 - Swift

Add these 2 lines

layout.minimumInteritemSpacing = 0
layout.minimumLineSpacing = 0

So you have:

   // Do any additional setup after loading the view, typically from a nib.
        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 20, left: 0, bottom: 10, right: 0)
        layout.itemSize = CGSize(width: screenWidth/3, height: screenWidth/3)
        layout.minimumInteritemSpacing = 0
        layout.minimumLineSpacing = 0
        collectionView!.collectionViewLayout = layout

That will remove all the spaces and give you a grid layout:

enter image description here

If you want the first column to have a width equal to the screen width then add the following function:

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    if indexPath.row == 0
    {
        return CGSize(width: screenWidth, height: screenWidth/3)
    }
    return CGSize(width: screenWidth/3, height: screenWidth/3);

}

Grid layout will now look like (I've also added a blue background to first cell): enter image description here

Solution 2 - Swift

For Swift 3 and XCode 8, this worked. Follow below steps to achieve this:-

{
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    let width = UIScreen.main.bounds.width
    layout.sectionInset = UIEdgeInsets(top: 0, left: 5, bottom: 0, right: 5)
    layout.itemSize = CGSize(width: width / 2, height: width / 2)
    layout.minimumInteritemSpacing = 0
    layout.minimumLineSpacing = 0
    collectionView!.collectionViewLayout = layout
}

Place this code into viewDidLoad() function.

Solution 3 - Swift

In Certain situations, Setting the UICollectionViewFlowLayout in viewDidLoador ViewWillAppear may not effect on the collectionView.

Setting the UICollectionViewFlowLayout in viewDidAppear may cause see the changes of the cells sizes in runtime.

Another Solution, in Swift 3 :

extension YourViewController : UICollectionViewDelegateFlowLayout{
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 20, left: 0, bottom: 10, right: 0)
    }
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let collectionViewWidth = collectionView.bounds.width
        return CGSize(width: collectionViewWidth/3, height: collectionViewWidth/3)
    }
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 20
    }
}

Solution 4 - Swift

If you are looking for Swift 3, Follow the steps to achieve this:

func viewDidLoad() {

    //Define Layout here
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()

    //Get device width
    let width = UIScreen.main.bounds.width

    //set section inset as per your requirement.
    layout.sectionInset = UIEdgeInsets(top: 0, left: 5, bottom: 0, right: 5)

    //set cell item size here 
    layout.itemSize = CGSize(width: width / 2, height: width / 2)

    //set Minimum spacing between 2 items
    layout.minimumInteritemSpacing = 0

    //set minimum vertical line spacing here between two lines in collectionview
    layout.minimumLineSpacing = 0

    //apply defined layout to collectionview
    collectionView!.collectionViewLayout = layout

}

This is verified on Xcode 8.0 with Swift 3.

Solution 5 - Swift

let layout = myCollectionView.collectionViewLayout as? UICollectionViewFlowLayout
layout?.minimumLineSpacing = 8

Solution 6 - Swift

Swift 4, Swift 5, Easiest Way!

No need create UICollectionViewFlowLayout() instance, just implement UICollectionViewDelegateFlowLayout on your Class.

extension MyCollectionView: UICollectionViewDelegateFlowLayout {

    // Distance Between Item Cells
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 20
    }
    
    // Cell Margin
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 16, left: 16, bottom: 16, right: 16)
    }

}

Solution 7 - Swift

Swift 4

let collectionViewLayout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout
collectionViewLayout?.sectionInset = UIEdgeInsetsMake(0, 20, 0, 40) 
collectionViewLayout?.invalidateLayout()

Solution 8 - Swift

Swift 5 : For evenly distributed spaces between cells with dynamic cell width to make the best of container space you may use the code snippet below by providing a minimumCellWidth value.

private func collectionViewLayout() -> UICollectionViewLayout {
    
    let layout = UICollectionViewFlowLayout()
    layout.sectionHeadersPinToVisibleBounds = true
    // Important: if direction is horizontal use minimumItemSpacing instead. 
    layout.scrollDirection = .vertical
    
    let itemHeight: CGFloat = 240
    let minCellWidth :CGFloat = 130.0
    let minItemSpacing: CGFloat = 10
    let containerWidth: CGFloat = self.view.bounds.width
    let maxCellCountPerRow: CGFloat =  floor((containerWidth - minItemSpacing) / (minCellWidth+minItemSpacing ))
    
    let itemWidth: CGFloat = floor( ((containerWidth - (2 * minItemSpacing) - (maxCellCountPerRow-1) * minItemSpacing) / maxCellCountPerRow  ) )
    // Calculate the remaining space after substracting calculating cellWidth (Divide by 2 because of left and right insets)
    let inset = max(minItemSpacing, floor( (containerWidth - (maxCellCountPerRow*itemWidth) - (maxCellCountPerRow-1)*minItemSpacing) / 2 ) )

    
    layout.itemSize = CGSize(width: itemWidth, height: itemHeight)
    layout.minimumInteritemSpacing = min(minItemSpacing,inset)
    layout.minimumLineSpacing = minItemSpacing
    layout.sectionInset = UIEdgeInsets(top: minItemSpacing, left: inset, bottom: minItemSpacing, right: inset)

    
    return layout
}

Solution 9 - Swift

instead of writing a line of code, we have an option in XCode, select CollectionView and go to navigator and change the "Min Spacing"

Solution 10 - Swift

For Swift 3 and XCode 8, this worked. Follow below steps to achieve this:-

viewDidLoad()
    {
        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        var width = UIScreen.main.bounds.width
        layout.sectionInset = UIEdgeInsets(top: 0, left: 5, bottom: 0, right: 5)
    width = width - 10
    layout.itemSize = CGSize(width: width / 2, height: width / 2)
        layout.minimumInteritemSpacing = 0
        layout.minimumLineSpacing = 0
        collectionView!.collectionViewLayout = layout
    }

Solution 11 - Swift

For Swift 3+ and Xcode 9+ Try using this

extension ViewController: UICollectionViewDelegateFlowLayout {

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    
    let collectionWidth = collectionView.bounds.width
    return CGSize(width: collectionWidth/3, height: collectionWidth/3)
    
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return 0
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
    return 0
    
}

Content Type	Original Author	Original Content on Stackoverflow
Question	Marko	View Question on Stackoverflow
Solution 1 - Swift	Peter Todd	View Answer on Stackoverflow
Solution 2 - Swift	Nirmit Dagly	View Answer on Stackoverflow
Solution 3 - Swift	Maor	View Answer on Stackoverflow
Solution 4 - Swift	Dharmendra Kachhadiya	View Answer on Stackoverflow
Solution 5 - Swift	jamal zare	View Answer on Stackoverflow
Solution 6 - Swift	Pengguna	View Answer on Stackoverflow
Solution 7 - Swift	Ahmadreza	View Answer on Stackoverflow
Solution 8 - Swift	deniz yalcin	View Answer on Stackoverflow
Solution 9 - Swift	logeshpalani31	View Answer on Stackoverflow
Solution 10 - Swift	Moin Shirazi	View Answer on Stackoverflow
Solution 11 - Swift	Aditya	View Answer on Stackoverflow