I am having trouble with auto layout again...
Here's what I want to get in the end:
I am doing everything in code with a Parent View Controller and Child View Controllers top, center and bottom.
In the end, I want to be able to set the height of the top view controller to its intrinsic height – that's where I am failing at right now... The top view controller has a vertical stack view used to place the elements (to be able to add and remove views as needed in the end).
This implementation...
import UIKit
class ParentViewController: UIViewController {
lazy var topChildView: UIView = {
let topView = topChildViewController.view!
topView.backgroundColor = .red
topView.translatesAutoresizingMaskIntoConstraints = false
topView.accessibilityIdentifier = "top"
return topView
}()
lazy var topChildViewController: TopChildViewController = {
let topVC = TopChildViewController()
return topVC
}()
lazy var centerChildView: UIView = {
let centerView = centerChildViewController.view!
centerView.backgroundColor = .blue
centerView.translatesAutoresizingMaskIntoConstraints = false
centerView.accessibilityIdentifier = "center"
return centerView
}()
lazy var centerChildViewController: CenterChildViewController = {
let centerVC = CenterChildViewController()
return centerVC
}()
lazy var bottomChildView: UIView = {
let bottomView = bottomChildViewController.view!
bottomView.backgroundColor = .green
bottomView.translatesAutoresizingMaskIntoConstraints = false
bottomView.accessibilityIdentifier = "bottom"
return bottomView
}()
lazy var bottomChildViewController: BottomChildViewController = {
let bottom = BottomChildViewController()
return bottom
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .gray
self.addChild(topChildViewController)
self.view.addSubview(topChildView)
self.addChild(centerChildViewController)
self.view.addSubview(centerChildView)
self.addChild(bottomChildViewController)
self.view.addSubview(bottomChildView)
NSLayoutConstraint.activate([
topChildView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 12),
topChildView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 12),
topChildView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -12),
topChildView.heightAnchor.constraint(equalToConstant: topChildView.intrinsicContentSize.height),
centerChildView.topAnchor.constraint(equalTo: topChildView.bottomAnchor),
centerChildView.leadingAnchor.constraint(equalTo: topChildView.leadingAnchor),
centerChildView.trailingAnchor.constraint(equalTo: topChildView.trailingAnchor),
bottomChildView.leadingAnchor.constraint(equalTo: topChildView.leadingAnchor),
bottomChildView.trailingAnchor.constraint(equalTo: topChildView.trailingAnchor),
bottomChildView.heightAnchor.constraint(equalToConstant: 100),
bottomChildView.topAnchor.constraint(equalTo: centerChildView.bottomAnchor),
bottomChildView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -12),
])
}
}
class TopChildViewController: UIViewController {
lazy var stackView: UIStackView = {
let s = UIStackView()
s.translatesAutoresizingMaskIntoConstraints = false
s.axis = .vertical
s.distribution = .fillEqually
s.spacing = 6
return s
}()
lazy var textField: UITextField = {
let t = UITextField()
t.borderStyle = .roundedRect
t.placeholder = "Some fancy text"
t.accessibilityIdentifier = "textfield"
t.translatesAutoresizingMaskIntoConstraints = false
return t
}()
lazy var label: UILabel = {
let l = UILabel()
l.accessibilityIdentifier = "label"
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "Awesome Label"
l.textAlignment = .center
return l
}()
override func loadView() {
view = UIView()
view.addSubview(stackView)
stackView.addArrangedSubview(textField)
stackView.addArrangedSubview(label)
NSLayoutConstraint.activate([
textField.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 12),
textField.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 12),
textField.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -12),
label.centerXAnchor.constraint(equalTo: view.centerXAnchor),
label.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -12)
])
}
}
class CenterChildViewController: UIViewController {
override func loadView() {
view = UIView()
}
}
class BottomChildViewController: UIViewController {
override func loadView() {
view = UIView()
}
}
...leads to this outcome:
While I am aware of the error (the intrinsic height does not seem to be available at the time I am trying to access it, see below), I don't know how to resolve it – what am I missing?
Does the constraint need to get created someplace else? I'd really like to be able to have control over it from the parent view controller...
[LayoutConstraints] Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. ( "<NSLayoutConstraint:0x600002306d50 top.height == - 1 (active, names: top:0x7f81c1e1f120 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x600002306d50 top.height == - 1 (active, names: top:0x7f81c1e1f120 )> Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful.
