How to add UITextField programmatically to UIScrollView without breaking constraints? - ios

Question

The case goes like this: I have a form embed in a UIScrollView, in the form there's a part where the user can add N numbers of textField, so if at first I had this:
UITextField - textField1
UIButton - Add
When Add is pressed I want to have this:
UITextField - textField1
UITextField - textField2
UIButton - Add
And although the text field is added, the constraints cannot be satisfied and therefore the UI breaks
The log for that:
[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.
(
"<_UILayoutSupportConstraint:0x1c4c800a0 _UILayoutGuide:0x106ccf4e0.height == 64 (active)>",
"<_UILayoutSupportConstraint:0x1c4c80050 V:|-(0)-[_UILayoutGuide:0x106ccf4e0] (active, names: '|':UIView:0x106ccdc10 )>",
"<_UILayoutSupportConstraint:0x1c4c80ff0 _UILayoutGuide:0x106ccf6d0.height == 0 (active)>",
"<_UILayoutSupportConstraint:0x1c4c801e0 _UILayoutGuide:0x106ccf6d0.bottom == UIView:0x106ccdc10.bottom (active)>",
"<NSLayoutConstraint:0x1c4c80550 UIImageView:0x106cce6c0.height == 5 (active)>",
"<NSLayoutConstraint:0x1c4c80640 UILabel:0x106ccf070'Completa tu Perfil'.height == 24 (active)>",
"<NSLayoutConstraint:0x1c0c886b0 form-view.height == 579 (active, names: form-view:0x10ed307c0 )>",
"<NSLayoutConstraint:0x1c0c8a1e0 V:|-(0)-[form-view] (active, names: form-view:0x10ed307c0, '|':UIScrollView:0x107a37000 )>",
"<NSLayoutConstraint:0x1c0c8a320 V:[form-view]-(0)-[profiles-view] (active, names: profiles-view:0x106ccd430, form-view:0x10ed307c0 )>",
"<NSLayoutConstraint:0x1c4c80af0 V:[_UILayoutGuide:0x106ccf4e0]-(10)-[UILabel:0x106ccf070'Completa tu Perfil'] (active)>",
"<NSLayoutConstraint:0x1c4c80cd0 V:[UILabel:0x106ccf070'Completa tu Perfil']-(8)-[UIImageView:0x106cce6c0] (active)>",
"<NSLayoutConstraint:0x1c4c80d20 V:[UIImageView:0x106cce6c0]-(0)-[UIScrollView:0x107a37000] (active)>",
"<NSLayoutConstraint:0x1c4c80e10 UIImageView:0x106ccddf0.top == profiles-view.top (active, names: profiles-view:0x106ccd430 )>",
"<NSLayoutConstraint:0x1c4c80f00 V:[UIImageView:0x106ccddf0]-(0)-[_UILayoutGuide:0x106ccf6d0] (active)>",
"<NSLayoutConstraint:0x1c0c8bdb0 'UIView-Encapsulated-Layout-Height' UIView:0x106ccdc10.height == 667 (active)>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1c0c886b0 form-view.height == 579 (active, names: form-view:0x10ed307c0 )>
So, since the height constraint was broken, AutoLayout arrange the elements following the margin constraints which allows the views broke that way.
That being said, the way I am adding the constraints is this:
func addModelButtonAction(_ sender: Any) { // an IBAction
addButton.isHighlighted = false
let last = modelTextFields.last!
let textField = last.createCopy() // extension method for creating a copy of the last textField
modelTextFieldsView.insertSubview(textField, belowSubview: last)
let growth = last.frame.height + 8 // the 8 represents the top spacing between textFields
formViewHeight.constant += growth // increasing height of the view where the form is embeded
modelTextFieldsHeight.constant += growth // increasing height of the view where the textFields are embeded
UIView.animate(withDuration: 0.5) {
self.view.layoutIfNeeded()
textField.frame.origin.y += growth // moving new textField below the previous one
}
modelTextFields.append(textField) // array of UITextField to keep track of the textFields in screen
}
And the view's alignment rectangles:
And the view's hierarchy:
What can I do to make this work as expected? I appreciate your help in this, because I've been trying to figure this out without any success.
Thanks in advance!

Answer 1

You have a couple of options to solve this layout issue:
Personally, I might try embedding these views in a UIStackView. The stack view will work to manage the vertical layout for you, allowing you to insert and remove subviews as needed. UIStackView is especially easy to work with from Interface Builder if you use Storyboards.
Alternatively, you could use a UITableView for this layout; it would manage the vertical flow on your behalf, abstracting much of the layout headache from you, though you'd need to manage the data source and cells yourself.
You could probably get this layout to work without either of these by carefully managing the priority of different constraints, allowing some to be broken as the layout changes, but this can be a tedious chore.