Why my 2D UIViews don't appear on screen? - ios

Question

I'm trying to make UIView that contains 12x7 UIViews with margins. I thought that the best way gonna be make 7 Vertical Stacks and then add all them on one big Horizontal stack. And I coded it, but problem is that this Horizontal Stacks doesn't appear on the screen at all (I've tried Xcode feature to see layers there is nothing).
This is my code:
import UIKit
class CalendarView: UIView {
override init(frame: CGRect) {
super.init(frame: frame)
setupView()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
setupView()
}
private func setupView() {
// array to add in future in columnsStackView
var columnStacks: [UIStackView] = []
for columns in 1...12 {
// array to add in future in columnStackView
var columnViews: [UIView] = []
for cell in 1...7 {
let cellView = UIView(frame: CGRect(x: 0, y: 0, width: 24, height: 24))
cellView.backgroundColor = .orange
columnViews.append(cellView)
}
// create columnStackView and add all 7 views
let columnStackView = UIStackView(arrangedSubviews: columnViews)
columnStackView.axis = .vertical
columnStackView.distribution = .fillEqually
columnStackView.alignment = .fill
columnStackView.spacing = 4
columnStacks.append(columnStackView)
}
// create columnsStackView and add those 12 stacks
let columnsStackView = UIStackView(arrangedSubviews: columnStacks)
columnsStackView.axis = .horizontal
columnsStackView.distribution = .fillEqually
columnsStackView.alignment = .fill
columnsStackView.spacing = 4
columnsStackView.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(columnsStackView)
}
}
Can you please help me with that!!!

Answer 1

Couple things...
A UIStackView uses auto-layout when arranging its subviews, so this line:
let cellView = UIView(frame: CGRect(x: 0, y: 0, width: 24, height: 24))
will create a UIView, but the width and height will be ignored.
You need to set those with constraints:
for cell in 1...7 {
let cellView = UIView()
cellView.backgroundColor = .orange
// we want each "cellView" to be 24x24 points
cellView.widthAnchor.constraint(equalToConstant: 24.0).isActive = true
cellView.heightAnchor.constraint(equalTo: cellView.widthAnchor).isActive = true
columnViews.append(cellView)
}
Now, because we've explicitly set the width and height of the "cellViews" we can set the stack view .distribution = .fill (instead of .fillEqually).
Next, we have to constrain the "outer" stack view (columnsStackView) to the view itself:
// constrain the "outer" stack view to self
NSLayoutConstraint.activate([
columnsStackView.topAnchor.constraint(equalTo: topAnchor),
columnsStackView.leadingAnchor.constraint(equalTo: leadingAnchor),
columnsStackView.trailingAnchor.constraint(equalTo: trailingAnchor),
columnsStackView.bottomAnchor.constraint(equalTo: bottomAnchor),
])
otherwise, the view will have 0x0 dimensions.
Here is a modified version of your class:
class CalendarView: UIView {
override init(frame: CGRect) {
super.init(frame: frame)
setupView()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
setupView()
}
private func setupView() {
// array to add in future in columnsStackView
var columnStacks: [UIStackView] = []
for columns in 1...12 {
// array to add in future in columnStackView
var columnViews: [UIView] = []
for cell in 1...7 {
let cellView = UIView()
cellView.backgroundColor = .orange
// we want each "cellView" to be 24x24 points
cellView.widthAnchor.constraint(equalToConstant: 24.0).isActive = true
cellView.heightAnchor.constraint(equalTo: cellView.widthAnchor).isActive = true
columnViews.append(cellView)
}
// create columnStackView and add all 7 views
let columnStackView = UIStackView(arrangedSubviews: columnViews)
columnStackView.axis = .vertical
columnStackView.distribution = .fill
columnStackView.alignment = .fill
columnStackView.spacing = 4
columnStacks.append(columnStackView)
}
// create columnsStackView and add those 12 stacks
let columnsStackView = UIStackView(arrangedSubviews: columnStacks)
columnsStackView.axis = .horizontal
columnsStackView.distribution = .fill
columnsStackView.alignment = .fill
columnsStackView.spacing = 4
columnsStackView.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(columnsStackView)
// constrain the "outer" stack view to self
NSLayoutConstraint.activate([
columnsStackView.topAnchor.constraint(equalTo: topAnchor),
columnsStackView.leadingAnchor.constraint(equalTo: leadingAnchor),
columnsStackView.trailingAnchor.constraint(equalTo: trailingAnchor),
columnsStackView.bottomAnchor.constraint(equalTo: bottomAnchor),
])
}
}
and a simple test controller to show how it can be used:
class CalendarTestViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let cv = CalendarView()
cv.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(cv)
// the CalendarView will size itself, so we only need to
// provide x and y position constraints
NSLayoutConstraint.activate([
cv.centerXAnchor.constraint(equalTo: view.centerXAnchor),
cv.centerYAnchor.constraint(equalTo: view.centerYAnchor),
])
// let's give it a background color so we can see its frame
cv.backgroundColor = .systemYellow
}
}
the result: