Error UIScrollView in swift 3 - ios

Question

I have a view that is composed of an image, a form with 11 UITextfield and a button, but the form is too big for my screen that is why I tried to use a UIScrollview.
The error I have is that my UIScrollview does not work as I can solve this problem.
This is my code:
import UIKit
class LoginCtrl: UIViewController {
let scrollView: UIScrollView = {
let sv = UIScrollView(frame: UIScreen.main.bounds)
sv.isScrollEnabled = true
sv.contentSize = CGSize(width: 2000, height: 5678)
sv.translatesAutoresizingMaskIntoConstraints = false
return sv
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor(r: 0, g: 150, b: 136)
self.view.addSubview(scrollView)
scrollView.addSubview(contenedorCampos)
setear_posicion_scrollView()
setear_posicion_contenedor()
}
func setear_posicion_scrollView(){
//definir x,y,width,height constraints
scrollView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
scrollView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
scrollView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
}
var heightContenedor: NSLayoutConstraint?
func setear_posicion_contenedor(){
//definir x,y,width,height constraints
contenedorCampos.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
contenedorCampos.topAnchor.constraint(equalTo: tabsInicio.bottomAnchor, constant: 12).isActive = true
contenedorCampos.widthAnchor.constraint(equalTo: view.widthAnchor, constant: -24).isActive = true
heightContenedor = contenedorCampos.heightAnchor.constraint(equalToConstant: 400)
heightContenedor?.isActive = true
contenedorCampos.addSubview(txtNombres)
contenedorCampos.addSubview(divider_txtNombres)....
}
}
Thanks

Answer 1

You've defined the relationship between the scrollview and its superview(which defines its frame), but not the relationship between the scrollview and its subviews (which defines its contentSize). As a result, the actual contentSize of the scrollview will be just be (0, 0).
In other words, you never actually laid anything out, at least not in the code you posted.
What you need to do is define layout constraints for the actual child views (everything that is a subview of the scrollview). Make sure to set up constraints definitively pinning these components to the edges of their parent (the scrollview). Once you have defined the constraints sufficiently, the scrollview should have a content size.
Technical note about this
In general, Auto Layout considers the top, left, bottom, and right
edges of a view to be the visible edges. That is, if you pin a view to
the left edge of its superview, you’re really pinning it to the
minimum x-value of the superview’s bounds. Changing the bounds origin
of the superview does not change the position of the view.
The UIScrollView class scrolls its content by changing the origin of
its bounds. To make this work with Auto Layout, the top, left, bottom,
and right edges within a scroll view now mean the edges of its content
view.
The constraints on the subviews of the scroll view must result in a
size to fill, which is then interpreted as the content size of the
scroll view. (This should not be confused with the
intrinsicContentSize method used for Auto Layout.) To size the scroll
view’s frame with Auto Layout, constraints must either be explicit
regarding the width and height of the scroll view, or the edges of the
scroll view must be tied to views outside of its subtree.