Add UIStackView as a customview of a UIBarButtonItem - swift

Question

I try to add a UIStackView as a custom view of a UIBarButtonItem.
I first tried adding a UIView as the custom view.
let list = UIView(frame: CGRect(x: 0, y: 0, width: 250, height: 44))
list.backgroundColor = .green
list.addSubview(stackView)
let item = UIBarButtonItem(customView: list )
topViewController?.setToolbarItems([item], animated: true)
This works. I get a green bar in the UIToolBar. Then I tried adding a UIStackView to the UIView.
let red = UIView(frame: CGRect(x: 0, y: 0, width: 250, height: 30))
red.backgroundColor = .red
let stackView = UIStackView(frame: CGRect(origin: CGPoint.zero,
size: CGSize(width: 250, height: 44)))
stackView.distribution = .fillEqually
stackView.axis = .horizontal
stackView.spacing = 5
stackView.alignment = .center
stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.addArrangedSubview(red)
let list = UIView(frame: CGRect(x: 0, y: 0, width: 250, height: 44))
list.backgroundColor = .green
list.addSubview(stackView)
let item = UIBarButtonItem(customView: list )
topViewController?.setToolbarItems([item], animated: true)
However, when I try this, nothing happens. The UIToolBar seems empty. What am I doing wrong?

Answer 1

In this answer, I have used two UIViews.
You have to give height constraints for two UIViews
red.heightAnchor.constraint(equalToConstant: 30).isActive = true;
green.heightAnchor.constraint(equalToConstant: 30).isActive = true;
You have to comment this line,
//stackView.translatesAutoresizingMaskIntoConstraints = false
Full Code:
self.navigationController?.isToolbarHidden = false
let red = UIView(frame: CGRect(x: 0, y: 0, width: 10, height: 30))
red.backgroundColor = .red
let green = UIView(frame: CGRect(x: 0, y: 0, width: 10, height: 30))
green.backgroundColor = .green
red.heightAnchor.constraint(equalToConstant: 30).isActive = true;
green.heightAnchor.constraint(equalToConstant: 30).isActive = true;
let stackView = UIStackView(frame: CGRect(x: 0, y: 0, width: 250, height: 30))
stackView.distribution = .fillEqually
stackView.axis = .horizontal
stackView.spacing = 5
stackView.alignment = .center
//stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.addArrangedSubview(red)
stackView.addArrangedSubview(green)
let list = UIView(frame: CGRect(x: 0, y: 0, width: 250, height: 44))
list.backgroundColor = .yellow
list.addSubview(stackView)
let item = UIBarButtonItem(customView: list )
self.setToolbarItems([item], animated: true)
Output: