Ios swift - How to create a grid of 3xInfinity items in Swift

Jos233Luna
May 23, 2023
169 views
0 votes
2 Answers

I am trying to create a grid of 3xInfinity items in Swift with same size items. The items are square buttons that can be aligned up to 3 items wide and infinite on the Y axis. I have created a function that takes a UIStackView with axis vertical and every 3 items I create a new UIStackView with horizontal axis inside of the other one. This works well but only when all the buttons are multiple of 3. Whenever they are not the row makes the buttons fill all the available space.

I would like to know how to create a grid of 3xInfinity items in Swift so that the buttons are always evenly spaced, even if there is an odd number of buttons.

How currently is displayed

How it should be displayed

Code

let stackview = UIStackView()
contentView.addSubview(stackview)
stackview.axis = .vertical
stackview.alignment = .fill
stackview.distribution = .fill
stackview.spacing = 10

 for _ in 0...feedButtonRows {
            let hstack = UIStackView()
            hstack.axis = .horizontal
            hstack.alignment = .center
            hstack.distribution = .fillEqually
            hstack.spacing = 16
            hstack.translatesAutoresizingMaskIntoConstraints = false
            hstack.widthAnchor.constraint(equalToConstant: stackview.frame.size.width).isActive = true
            for _ in 0..<3 {
                if(count == buttons.count){
                    
                    break
                }
                let button = FoodButtonComponent(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
                hstack.addArrangedSubview(button)
                button.widthAnchor.constraint(equalToConstant: 100).isActive = true
                button.heightAnchor.constraint(equalToConstant: 100).isActive = true
                button.setup(with: buttons[count])
                count+=1
            }
            stackview.addArrangedSubview(hstack)
        }

Answers

You can’t have distribution = .fillEqually and then at the same time expect that constraining your view size will have any effect using widthAnchor.constraint(equalToConstant: 100).isActive = true. You must be getting some runtime warnings about constraints being in conflict.

Also when using constraints remember to disable auto-translation of resizing mask into constraints for in-code-generated views.

let button = FoodButtonComponent(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
button.translatesAutoresizingMaskIntoConstraint = false

Anyway, you can still do what you want by simply adding an empty view instead of breaking when index goes past 3. You can actually create a standalone method to layout your views. Check out this implementation:

func layoutViewsVertically(_ views: [UIView], numberOfItemsPerRow: Int, horizontalSpacing: CGFloat = 0, verticalSpacing: CGFloat = 0) -> UIStackView {
    let verticalStackView = UIStackView()
    verticalStackView.axis = .vertical
    verticalStackView.distribution = .fillEqually
    verticalStackView.spacing = verticalSpacing
    
    var viewsToLayout = views
    while viewsToLayout.isEmpty == false {
        let horizontalStackView = UIStackView()
        horizontalStackView.spacing = horizontalSpacing
        horizontalStackView.translatesAutoresizingMaskIntoConstraints = false
        horizontalStackView.axis = .horizontal
        horizontalStackView.distribution = .fillEqually
        (0..<numberOfItemsPerRow).forEach { _ in
            let view = viewsToLayout.isEmpty ? UIView() : viewsToLayout.removeFirst()
            horizontalStackView.addArrangedSubview(view)
        }
        verticalStackView.addArrangedSubview(horizontalStackView)
    }
    return verticalStackView
}

I can now use this in multiple ways. For instance this will fill the size of a parent:

let views: [UIView] = (0..<20).map { index in
    let view = [UILabel(), UIButton()].randomElement()!
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor = [.red, .blue, .green].randomElement()!
    return view
}
let stackedView = StacksView.layoutViewsVertically(views, numberOfItemsPerRow: 3)
stackedView.frame = view.bounds
view.addSubview(stackedView)

Or you can have some implicit size defined by views inside the stack view

let views: [UIView] = (0..<20).map { index in
    let view = [UILabel(), UIButton()].randomElement()!
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor = [.red, .blue, .green].randomElement()!
    view.heightAnchor.constraint(equalToConstant: 50).isActive = true
    view.widthAnchor.constraint(equalToConstant: 50).isActive = true
    return view
}
let stackedView = StacksView.layoutViewsVertically(views, numberOfItemsPerRow: 3)
stackedView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(stackedView)

Or you can have something in-between where width is constrained by parent but height is not:

let views: [UIView] = (0..<20).map { index in
    let view = [UILabel(), UIButton()].randomElement()!
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor = [.red, .blue, .green].randomElement()!
    view.heightAnchor.constraint(equalToConstant: 50).isActive = true
    return view
}
let stackedView = StacksView.layoutViewsVertically(views, numberOfItemsPerRow: 3)
stackedView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(stackedView)
stackedView.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 1.0).isActive = true

If you set your vertical stack view’s .alignment = .leading and do not give the horizontal "row" stack views width constraints, the buttons will be left-aligned and won’t get stretched.

You can also simplify your code a bit like this:

    var i: Int = 0
    
    while i < numButtons {
        let hstack = UIStackView()
        hstack.axis = .horizontal
        hstack.spacing = 16
        for _ in 0..<3 {
            if i < numButtons {
                let button = FoodButtonComponent()
                button.setTitle("(i)", for: [])
                button.widthAnchor.constraint(equalToConstant: 100.0).isActive = true
                button.heightAnchor.constraint(equalTo: button.widthAnchor).isActive = true
                hstack.addArrangedSubview(button)
            }
            i += 1
        }
        stackview.addArrangedSubview(hstack)
    }

Note that when views (labels, buttons, etc) are added as arrangedSubviews of a stack view, UIKit automatically sets .translatesAutoresizingMaskIntoConstraints = false — so no need to explicitly set that.

Here’s a complete example – change the numButtons at the top to see the layouts:

class StacksVC: UIViewController {
    
    let numButtons: Int = 7
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemBackground
        
        let stackview = UIStackView()
        stackview.axis = .vertical
        // this will keep the 1- & 2-button rows left-aligned
        stackview.alignment = .leading
        stackview.distribution = .fill
        stackview.spacing = 10
        
        var i: Int = 0
        
        while i < numButtons {
            let hstack = UIStackView()
            hstack.axis = .horizontal
            hstack.spacing = 16
            for _ in 0..<3 {
                if i < numButtons {
                    let button = FoodButtonComponent()
                    button.setTitle("(i)", for: [])
                    button.widthAnchor.constraint(equalToConstant: 100.0).isActive = true
                    button.heightAnchor.constraint(equalTo: button.widthAnchor).isActive = true
                    hstack.addArrangedSubview(button)
                }
                i += 1
            }
            stackview.addArrangedSubview(hstack)
        }
        
        stackview.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(stackview)
        
        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            stackview.topAnchor.constraint(equalTo: g.topAnchor, constant: 20.0),
            stackview.centerXAnchor.constraint(equalTo: g.centerXAnchor),
            // set stackview width to (3 x 100) + (2 x 16)
            //  so if we have only 1 or 2 buttons, they will be "left-aligned"
            stackview.widthAnchor.constraint(equalToConstant: 332.0),
        ])
        
        // let's set the vertical stackview background to light gray
        //  if we want to see the framing
        //stackview.backgroundColor = UIColor(white: 0.9, alpha: 1.0)

    }
    
}

When run: