Swift: Center NSAttributedString in View horizontally and vertically - swift

Question

Hi there,
I have a class CardButton: UIButton . In the draw method of this CardButton, I would like to add and center(vertically and horizontally) NSAttributed String, which is basically just one Emoji, inside of it. The result would look something like this:
However, NSAttributedString can be only aligned to center in horizontal dimension inside the container.
My idea for solution:
create a containerView inside of CardButton
center containerView both vertically and horizontally in it's container(which is CardButton)
add NSAttributedString inside the containerView and size containerView to fit the string's font.
So the result would look something like this:
My attempt for this to happen looks like this:
class CardButton: UIButton {
override func draw(){
//succesfully drawing the CardButton
let stringToDraw = attributedString(symbol, fontSize: symbolFontSize) //custom method to create attributed string
let containerView = UIView()
containerView.backgroundColor = //green
addSubview(containerView)
containerView.translatesAutoresizingMaskIntoConstraints = false
let centerXConstraint = containerView.centerXAnchor.constraint(equalTo: (self.centerXAnchor)).isActive = true
let centerYConstraint = containerView.centerYAnchor.constraint(equalTo: (self.centerYAnchor)).isActive = true
stringToDraw.draw(in: containerView.bounds)
containerView.sizeToFit()
}
}
Long story short, I failed terribly. I first tried to add containerView to cardButton, made the background green, gave it fixed width and height jut to make sure that it got properly added as a subview. It did. But once I try to active constraints on it, it totally disappears.
Any idea how to approach this?

Answer 1

There is always more than one way to achieve any particular UI design goal, but the procedure below is relatively simple and has been adapted to suit the requirements as presented and understood in your question.
The UIButton.setImage method allows an image to be assigned to a UIButton without the need for creating a container explicitly.
The UIGraphicsImageRenderer method allows an image to be made from various components including NSAttributedText, and a host of custom shapes.
The process utilising these two tools to provide the rudiments for your project will be to:
Render an image with the appropriate components & size
Assign the rendered image to the button
A class could be created for this functionality, but that has not been explored here.
Additionally, your question mentions that when applying constraints the content disappears. This effect can be observed when image dimensions are too large for the container, constraints are positioning the content out of view and possibly a raft of other conditions.
The following code produces the above image:
func drawRectangleWithEmoji() -> UIImage {
let renderer = UIGraphicsImageRenderer(size: CGSize(width: 512, height: 512))
let img = renderer.image { (ctx) in
// Create the outer square:
var rectangle = CGRect(x: 0, y: 0, width: 512, height: 512).insetBy(dx: 7.5, dy: 7.5)
var roundedRect = UIBezierPath(roundedRect: rectangle, cornerRadius: 50).cgPath
// MARK: .cgPath creates a CG representation of the path
ctx.cgContext.setFillColor(UIColor.white.cgColor)
ctx.cgContext.setStrokeColor(UIColor.blue.cgColor)
ctx.cgContext.setLineWidth(15)
ctx.cgContext.addPath(roundedRect)
ctx.cgContext.drawPath(using: .fillStroke)
// Create the inner square:
rectangle = CGRect(x: 0, y: 0, width: 512, height: 512).insetBy(dx: 180, dy: 180)
roundedRect = UIBezierPath(roundedRect: rectangle, cornerRadius: 10).cgPath
ctx.cgContext.setFillColor(UIColor.green.cgColor)
ctx.cgContext.setStrokeColor(UIColor.green.cgColor)
ctx.cgContext.setLineWidth(15)
ctx.cgContext.addPath(roundedRect)
ctx.cgContext.drawPath(using: .fillStroke)
// Add emoji:
var fontSize: CGFloat = 144
var attrs: [NSAttributedString.Key: Any] = [
.font: UIFont.systemFont(ofSize: fontSize)//,
//.backgroundColor: UIColor.gray //uncomment to see emoji background bounds
]
var string = "❤️"
var attributedString = NSAttributedString(string: string, attributes: attrs)
let strWidth = attributedString.size().width
let strHeight = attributedString.size().height
attributedString.draw(at: CGPoint(x: 256 - strWidth / 2, y: 256 - strHeight / 2))
// Add NSAttributedString:
fontSize = 56
attrs = [
.font: UIFont.systemFont(ofSize: fontSize),
.foregroundColor: UIColor.brown
]
string = "NSAttributedString"
attributedString = NSAttributedString(string: string, attributes: attrs)
let textWidth = attributedString.size().width
let textHeight = attributedString.size().height
attributedString.draw(at: CGPoint(x: 256 - textWidth / 2, y: 384 - textHeight / 2))
}
return img
}
Activate the NSLayoutContraints and then the new image can be set for the button:
override func viewDidLoad() {
super.viewDidLoad()
view = UIView()
view.backgroundColor = .white
let buttonsView = UIView()
buttonsView.translatesAutoresizingMaskIntoConstraints = false
// buttonsView.backgroundColor = UIColor.gray
view.addSubview(buttonsView)
NSLayoutConstraint.activate([
buttonsView.widthAnchor.constraint(equalToConstant: CGFloat(buttonWidth)),
buttonsView.heightAnchor.constraint(equalToConstant: CGFloat(buttonWidth)),
buttonsView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
buttonsView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
])
let cardButton = UIButton(type: .custom)
cardButton.contentEdgeInsets = UIEdgeInsets(top: 5, left: 5, bottom: 5, right: 5)
cardButton.setImage(drawRectangleWithEmoji(), for: .normal)
let frame = CGRect(x: 0, y: 0, width: buttonWidth, height: buttonWidth)
cardButton.frame = frame
buttonsView.addSubview(cardButton)
}
Your comments will be appreciated as would constructive review of the code provided.