I am adding a child view using the View.addChild method
The containing view is clearly 350 pixels. However, the child view takes up ALL the space of the containing view....so my idea is to force the child view to be smaller than its parent...but my code does not work. I can tell you that if I uncomment the two lines it almost works, but then the child view does not occupy the size that I want it to and it blocks other elements. Here is where I am:
child.view.translatesAutoresizingMaskIntoConstraints = false
let safeArea = view.layoutMarginsGuide
//child.view.topAnchor.constraint(equalTo: tableContainer.topAnchor).isActive = true
// child.view.bottomAnchor.constraint(equalTo: tableContainer.bottomAnchor).isActive = true
child.view.leftAnchor.constraint(equalTo: tableContainer.leftAnchor).isActive = true
child.view.rightAnchor.constraint(equalTo: tableContainer.rightAnchor).isActive = true
child.view.heightAnchor.constraint(equalToConstant: 250).isActive = true
self.addChild(child)
Let me state very clearly, my goal is to get the child view to 250 pixels. Thank you.
Your solution might look something like this.
child.view.translatesAutoresizingMaskIntoConstraints = false
let safeArea = view.layoutMarginsGuide
//Your left and right anchors tell the compiler exactly how wide the view should be.
//If you have it set to equal both then the view MUST be exactly the width of parent.
child.view.leftAnchor.constraint(equalTo: tableContainer.leftAnchor).isActive = true
child.view.rightAnchor.constraint(equalTo: tableContainer.rightAnchor).isActive = true
//Since you're defining your own height here you need to explicitly state where the
//view starts at. If you don't define a top, center, bottom or some other constraint
//it's impossible to know where to put the view.
child.view.heightAnchor.constraint(equalToConstant: 250).isActive = true
child.view.topAnchor.constraint(equalTo: safeArea.topAnchor).isActive = true
self.addChild(child)
The reason for this is that when creating anchors, you MUST have an X & Y anchors for all views, even logically. For example if you define a width of 100 and a height of 100 you've created a square, but where does that square go? You don't have an X or a Y in that example. However, if you define a width to match the parent view using the left and right anchor then it knows the width of the view just by the anchors on the left and right. The same principle applies to a top and bottom anchor. If you define a top and bottom anchor then it will be the size of the view (Given that you set them equalTo) and it will know the height.
In your instance, you've defined height of 250 however it doesn't know where to start at. Does it start at the top, middle, bottom, it doesn't have a clue because you haven't set it. The IDE is very literal with constraints and no obscurity will work.
Related
(Xcode 11, Swift)
Being a newbie to iOS and Autolayout, I'm struggling with implementing a fairly simple (IMHO) view which displays a [vertical] list of items. The only problem is that items are decided dynamically and each of them could be either text or image (where either of those could be fairly large so scrolling would be required). WebView is not an option, so it has to be implemented natively.
This is how I understand the process:
Make in IB a UIScrollView and size it to the size of the outer frame.
Make a container view as a subview of UIScrollView (again, in IB) and size it the same.
Set constraint on equal width of both
At runtime, populate container view with UILabels/UIImageViews and also set constraints programmatically to ensure proper layout.
"Tell" scrollview about the subview height in order to make it manage the scrolling thereof.
Is this the right approach? It doesn't seem to work for me (for a toy example of dynamically adding a very tall image to a container view - I cannot get the scrolling to work). What would be the proper way to do the last step in the process above - just force the contentSize of the scrollview to the size of the populated container view (it doesn't seem to work for me). Any help would be appreciated.
When adding multiple elements to a scroll view at run-time, you may find it much easier to use a UIStackView... when setup properly, it will automatically grow in height with each added object.
As a simple example...
1) Start by adding a UIScrollView (I gave it a blue background to make it easier to see). Constrain it to Zero on all 4 sides:
Note that we see the "red circle" indicating missing / conflicting constraints. Ignore that for now.
2) Add a UIView as a "content view" to the scroll view (I gave it a systemYellow background to make it easier to see). Constrain it to Zero on all 4 sides to the Content Layout Guide -- this will (eventually) define the scroll view's content size. Also constrain it equal width and equal height to the Frame Layout Guide:
Important Step: Select the Height constraint, and in the Size Inspector pane select the Placeholder - Remove at build time checkbox. This will satisfy auto-layout in IB during design time, but will allow the height of that view to shrink / grow as necessary.
3) Add a Vertical UIStackView to the "content view". Constrain it to Zero on all 4 sides. Configure its properties to Fill / Fill / 8 (as shown below):
4) Add an #IBOutlet connection to the stack view in your view controller class. Now, at run-time, as you add UI elements to the stack view, all of your "scrollability" will be handled by auto-layout.
Here is an example class:
class DynaScrollViewController: UIViewController {
#IBOutlet var theStackView: UIStackView!
override func viewDidLoad() {
super.viewDidLoad()
// local var so we can reuse it
var theLabel = UILabel()
var theImageView = UIImageView()
// create a new label
theLabel = UILabel()
// this gets set to false when the label is added to a stack view,
// but good to get in the habit of setting it
theLabel.translatesAutoresizingMaskIntoConstraints = false
// multi-line
theLabel.numberOfLines = 0
// cyan background to make it easy to see
theLabel.backgroundColor = .cyan
// add 9 lines of text to the label
theLabel.text = (1...9).map({ "Line \($0)" }).joined(separator: "\n")
// add it to the stack view
theStackView.addArrangedSubview(theLabel)
// add another label
theLabel = UILabel()
// multi-line
theLabel.numberOfLines = 0
// yellow background to make it easy to see
theLabel.backgroundColor = .yellow
// add 5 lines of text to the label
theLabel.text = (1...5).map({ "Line \($0)" }).joined(separator: "\n")
// add it to the stack view
theStackView.addArrangedSubview(theLabel)
// create a new UIImageView
theImageView = UIImageView()
// this gets set to false when the label is added to a stack view,
// but good to get in the habit of setting it
theImageView.translatesAutoresizingMaskIntoConstraints = false
// load an image for it - I have one named background
if let img = UIImage(named: "background") {
theImageView.image = img
}
// let's give the image view a 4:3 width:height ratio
theImageView.widthAnchor.constraint(equalTo: theImageView.heightAnchor, multiplier: 4.0/3.0).isActive = true
// add it to the stack view
theStackView.addArrangedSubview(theImageView)
// add another label
theLabel = UILabel()
// multi-line
theLabel.numberOfLines = 0
// yellow background to make it easy to see
theLabel.backgroundColor = .green
// add 2 lines of text to the label
theLabel.text = (1...2).map({ "Line \($0)" }).joined(separator: "\n")
// add it to the stack view
theStackView.addArrangedSubview(theLabel)
// add another UIImageView
theImageView = UIImageView()
// this gets set to false when the label is added to a stack view,
// but good to get in the habit of setting it
theImageView.translatesAutoresizingMaskIntoConstraints = false
// load a different image for it - I have one named AquariumBG
if let img = UIImage(named: "AquariumBG") {
theImageView.image = img
}
// let's give this image view a 1:1 width:height ratio
theImageView.heightAnchor.constraint(equalTo: theImageView.widthAnchor, multiplier: 1.0).isActive = true
// add it to the stack view
theStackView.addArrangedSubview(theImageView)
}
}
If the steps have been followed, you should get this output:
and, after scrolling to the bottom:
Alignment constraints (leading/trailing/top/bottom)
The alignment constraint between Scroll View and Content View defines the scrollable range of the content. For example,
If scrollView.bottom = contentView.bottom, it means Scroll View is
scrollable to the bottom of Content View.
If scrollView.bottom = contentView.bottom + 100, the scrollable
bottom end of Scroll View will exceed the end of Content View by 100
points.
If scrollView.bottom = contentView.bottom — 100, the bottom of
Content View will not be reached even the scrollView is scrolled to
the bottom end.
That is, the (bottom) anchor on Scroll View indicates the (bottom) edge of the outer frame, i.e., the visible part of Content View; the (bottom) anchor on Content View refers to the edge of the actual content, which will be hidden if not scrolled to.
Unlike normal use cases, alignment constraints between Scroll View and Content View have nothing to do with the actual size of Content View. They affect only “scrollable range of content view” but NOT “actual content size”. The actual size of Content View must be additionally defined.
Size constraints (width/height)
To actually size Content View, we may set the size of Content View to a specific length, like width/height of 500. If the width/height exceeds the width/height of Scroll View, there will be a scrollbar for users to scroll.
However, a more common case will be, we want Content View to have the same width (or height) as Scroll View. In this case, we will have
contentView.width = scrollView.width
The width of Content View refers to the actual full width of content. On the other hand, the width of Scroll View refers to the outer container frame width of Scroll View. Of course, it doesn’t have to be the same width, but can be other forms like a * scrollView.width + b.
And if we have Content View higher (or wider) than Scroll View, a scrollbar appears.
Content View can not only be a single view, but also multiple views, as long as they are appropriately constrained using alignment and size constraints to Scroll View.
For details, you may follow this article: Link.
I want to set a centerYAnchor between two anchors. Similar to this:
centeredLabel.centerYAnchor.constraint(equalTo: view.centerYAnchor),
However, I don't want it to be centered relative to the screen. I want it to be right in between two other anchors on the screen. Like if I have a toolbar at the top like this:
toolbar.topAnchor.constraint(equalTo: view.topAnchor),
Then I have a button at the bottom like this:
button.bottomAnchor.constraint(equalTo: guide.bottomAnchor, constant: -20)
is there a way I can center centeredLabel's y constraint to be right between the bottomanchor of toolbar and the top anchor of button?
is there a way I can center centeredLabel's y constraint to be right between the bottomanchor of toolbar and the top anchor of button?
Yes, there is. The simple way is to use a transparent spacer view whose top is anchored to the upper anchor and whose bottom is anchored to the lower anchor. Now you center-anchor your label to the center of the spacer view.
However, although that is simple, it is not the best way. The best way is to create, instead of a transparent spacer view, a custom UILayoutGuide. Unfortunately this can be done only in code, not in the storyboard (whereas the spacer view and label can be configured entirely in the storyboard). But it has the advantage that it doesn't burden the rendering tree with an additional view.
Here's your situation, more or less, using a button as the upper view and a button as the lower view. The label is centered vertically between them:
Here's the code that generated that situation. b1 and b2 are the buttons (and it doesn't matter how they are created and positioned):
let g = UILayoutGuide()
self.view.addLayoutGuide(g)
g.topAnchor.constraint(equalTo: b1.bottomAnchor).isActive = true
g.bottomAnchor.constraint(equalTo: b2.topAnchor).isActive = true
g.leadingAnchor.constraint(equalTo:b1.leadingAnchor).isActive = true
g.trailingAnchor.constraint(equalTo:b1.trailingAnchor).isActive = true
let lab = UILabel()
lab.text = "Label"
lab.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(lab)
lab.leadingAnchor.constraint(equalTo:g.leadingAnchor).isActive = true
lab.centerYAnchor.constraint(equalTo:g.centerYAnchor).isActive = true
Although #matt's solution works, here is a simpler one that uses autolayout without the need to create a UILayoutGuide.
iOS 10 introduced a simple way of doing this through NSLayoutXAxisAnchor.anchorWithOffset(to:) and NSLayoutYAxisAnchor.anchorWithOffset(to:).
Here are convenience methods which wrap up this logic.
For X axis centering
extension NSLayoutXAxisAnchor {
func constraint(between anchor1: NSLayoutXAxisAnchor, and anchor2: NSLayoutXAxisAnchor) -> NSLayoutConstraint {
let anchor1Constraint = anchor1.anchorWithOffset(to: self)
let anchor2Constraint = anchorWithOffset(to: anchor2)
return anchor1Constraint.constraint(equalTo: anchor2Constraint)
}
}
For Y axis centering
extension NSLayoutYAxisAnchor {
func constraint(between anchor1: NSLayoutYAxisAnchor, and anchor2: NSLayoutYAxisAnchor) -> NSLayoutConstraint {
let anchor1Constraint = anchor1.anchorWithOffset(to: self)
let anchor2Constraint = anchorWithOffset(to: anchor2)
return anchor1Constraint.constraint(equalTo: anchor2Constraint)
}
}
To do what you need you can call:
centeredLabel.centerYAnchor.constraint(between: toolbar.bottomAnchor, and: button.topAnchor)
My original ViewController consists of only one scrollView like this:
Now I also have my own xib file (CheckBoxView) which mainly consists of one button, see this screenshot:
I dynamically create some UIStackViews and add them to the ScrollView Inside these UIStackViews I add multiple instances of my xib file.
What I want to achieve is, that the StackViews are just vertically stacked. And inside the StackViews the UIViews from my xib-file should also be vertically stacked.
At the moment it looks like this:
So the xib-Views are not in the whole view. Since I am using multi-os-engine I can't provide swift/obj-c code. But here is my Java-Code:
for (ItemConfiguration config : itemInstance.getConfigurations()) {
List<DLRadioButton> radioButtons = new ArrayList<DLRadioButton>();
UIStackView configView = UIStackView.alloc().initWithFrame(new CGRect(new CGPoint(0, barHeight), new CGSize(displayWidth, displayHeight - barHeight)));
configView.setAxis(UILayoutConstraintAxis.Vertical);
configView.setDistribution(UIStackViewDistribution.EqualSpacing);
configView.setAlignment(UIStackViewAlignment.Center);
configView.setSpacing(30);
for (ConfigurationOption option : config.getOptions()) {
UIView checkBox = instantiateFromNib("CheckBoxView");
for (UIView v : checkBox.subviews()) {
if (v instanceof DLRadioButton) {
((DLRadioButton) v).setTitleForState(option.getName(), UIControlState.Normal);
//((DLRadioButton) v).setIconSquare(true);
radioButtons.add((DLRadioButton) v);
}
}
configView.addArrangedSubview(checkBox);
}
// group radiobuttons
//groupRadioButtons(radioButtons);
configView.setTranslatesAutoresizingMaskIntoConstraints(false);
scrollView().addSubview(configView);
configView.centerXAnchor().constraintEqualToAnchor(scrollView().centerXAnchor()).setActive(true);
configView.centerYAnchor().constraintEqualToAnchor(scrollView().centerYAnchor()).setActive(true);
}
private UIView instantiateFromNib(String name) {
return (UIView) UINib.nibWithNibNameBundle(name, null).instantiateWithOwnerOptions(null, null).firstObject();
}
How do I need to set the Alignments etc. to Achieve what I want. It should look like this:
I don't know if there is a reason to not use UITableView, that i highly recommend for your case. In case it's not possible, below you can find some pieces of advice that should help.
If you use Auto Layout, you should set constraints for all views instantiated in your code. The constraints must be comprehensive for iOS to know each view's position and size.
Remove redundant constraints
configView.centerXAnchor().constraintEqualToAnchor(scrollView().centerXAnchor()).setActive(true);
configView.centerYAnchor().constraintEqualToAnchor(scrollView().centerYAnchor()).setActive(true);
These two constraint just doesn't make sense to me. You need the stackviews be stacked within you ScrollView, but not centered. If i understand you goal correctly, this should be removed
Set width/x-position constraints for UIStackViews
configView.setTranslatesAutoresizingMaskIntoConstraints(false);
scrollView().addSubview(configView);
Right after a stack view is added to the ScrollView, you need to set up constraints for it. I'll provide my code in swift, but it looks quite similar to what your Java code is doing, so hopefully you'll be able to transpile it without difficulties:
NSLayoutConstraint.activate([
configView.leadingAnchor.constraintEqualToAnchor(scrollView.leadingAnchor),
configView.trailingAnchor.constraintEqualToAnchor(scrollView.trailingAnchor)
]);
Set height constraints for UIStackViews
StackViews doesn't change their size whenever you add arranged view in it. So you need to calculate a desired stackview size yourself and specify it explicitly via constraints. It should be enough to accommodate items and spaces between them. I suppose that all items should be of the same size, let it be 32 points, then height should be:
let stackViewHeight = items.count * 32 + stackView.space * (items.count + 1)
And make new height constraint for the stack view:
configView.heightAnchor.constraint(equalToConstant: stackViewHeight).isActive = true
Set y-position for UIStackView
This is a little bit more challenging part, but the most important for the views to work properly in a scroll view.
1) Change loop to know the index of a UIStackView
A scroll view should always be aware of height of its content, so you need to understand which stack view is the top one, and which is the bottom. In order to do that, you need to change for each loop to be written as for(;;) loop:
for (int i = 0; i < itemInstance.getConfigurations().length; i++) {
ItemConfiguration config = itemInstance.getConfigurations()[i]
...
}
I'm not aware of which type your array is, so if it doesn't have subscript functionality, just replace it with corresponding method.
2) Set top anchor for stack views
For the first stack view in the array, top anchor should be equal to the scroll view top anchor, for others it should be bottom anchor of the previous stack view + spacing between them (say, 8 points in this example):
if i == 0 {
configView.topAnchor.constraintEqualToAnchor(scrollView.topAnchor, constant: 8).isActive = true
} else {
let previousConfigView = itemInstance.getConfigurations()[i - 1]
configView.topAnchor.constraintEqualToAnchor(previousConfigView.bottomAnchor, constant: 8).isActive = true
}
3) Set bottom anchor for the last stack view
As was said - for the Scroll View to be aware of content size, we need to specify corresponding constraints:
if i == itemInstance.getConfigurations() - 1 {
configView.bottomAnchor.constraintEqualToAnchor(scrollView.bottomAnchor, constant: 8).isActive = true
}
Note: please be advised, that all constraints should be set on views that are already added to the scroll view.
Imagine a stack view with four items, filling something. (Say, filling the screen).
Notice there are three gaps, ABC.
(Note - the yellow blocks are always some fixed height each.)
(Only the gaps change, depending on the overall height available to the stack view.)
Say UISV is able to draw everything, with say 300 left over. The three gaps will be 100 each.
In the example, 9 is left over, so A B and C are 3 each.
However.
Very often, you want the gaps themselves to enjoy a proportional relationship.
Thus - your designer may say something like
If the screen is too tall, expand the spaces at A, B and C. However. Always expand B let's say 4x as fast as the gaps at A and B."
So, if "12" is left over, that would be 2,8,2. Whereas when 18 is left over, that would be 3,12,3.
Is this concept available in stack view? Else, how would you do it?
(Note that recently added to stack view, you can indeed specify the gaps individually. So, it would be possible to do it "manually", but it would be a real mess, you'd be working against the solver a lot.)
You can achieve that by following workaround. Instead of spacing, for each space add a new UIView() that would be a stretchable space. And then just add constraints between heights of these "spaces" that would constrain their heights together based on the multipliers you want, so e.g.:
space1.heightAnchor.constraint(equalTo: space2.heightAnchor, multiplier: 2).isActive = true
And to make it work I think you'd have to add one constraint that would try to stretch those spaces in case there is free space:
let stretchingConstraint = space1.heightAnchor.constraint(equalToConstant: 1000)
// lowest priority to make sure it wont override any of the rest of constraints and compression resistances
stretchingConstraint.priority = UILayoutPriority(rawValue: 1)
stretchingConstraint.isActive = true
The "normal" content views would have to have intrinsic size or explicit constraints setting their heights to work properly.
Here is an example:
class MyViewController: UIViewController {
fileprivate let stack = UIStackView()
fileprivate let views = [UIView(), UIView(), UIView(), UIView()]
fileprivate let spaces = [UIView(), UIView(), UIView()]
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = .white
self.view.addSubview(stack)
// let stack fill the whole view
stack.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
stack.topAnchor.constraint(equalTo: self.view.topAnchor),
stack.bottomAnchor.constraint(equalTo: self.view.bottomAnchor),
stack.leftAnchor.constraint(equalTo: self.view.leftAnchor),
stack.rightAnchor.constraint(equalTo: self.view.rightAnchor),
])
stack.alignment = .fill
// distribution must be .fill
stack.distribution = .fill
stack.spacing = 0
stack.axis = .vertical
for (index, view) in views.enumerated() {
stack.addArrangedSubview(view)
view.translatesAutoresizingMaskIntoConstraints = false
// give it explicit height (or use intrinsic height)
view.heightAnchor.constraint(equalToConstant: 50).isActive = true
view.backgroundColor = .orange
// intertwin it with spaces
if index < spaces.count {
stack.addArrangedSubview(spaces[index])
spaces[index].translatesAutoresizingMaskIntoConstraints = false
}
}
// constraints for 1 4 1 proportions
NSLayoutConstraint.activate([
spaces[1].heightAnchor.constraint(equalTo: spaces[0].heightAnchor, multiplier: 4),
spaces[2].heightAnchor.constraint(equalTo: spaces[0].heightAnchor, multiplier: 1),
])
let stretchConstraint = spaces[0].heightAnchor.constraint(equalToConstant: 1000)
stretchConstraint.priority = UILayoutPriority(rawValue: 1)
stretchConstraint.isActive = true
}
}
Remarkably, #MilanNosáľ 's solution works perfectly.
You do not need to set any priorities/etc - it works perfectly "naturally" in the iOS solver!
Set the four content areas simply to 50 fixed height. (Use any intrinsic content items.)
Simply don't set the height at all of "gap1".
Set gap2 and gap3 to be equal height of gap1.
Simply - set the ratios you want for gap2 and gap3 !
Versus gap1.
So, gap2 is 0.512 the height of gap1, gap3 is 0.398 the height of gap1, etc.
It does solve it in all cases.
Fantastic!!!!!!!!!!
So: in the three examples (being phones with three different screen heights). In fact the relative heights of the gaps, is always the same. Your design department will rejoice! :)
Created: a gist with a storyboard example
The key here is Equal Heights between your arranged views and your reference view:
And then change the 'Multiplier` to your desired sizes:
In this example I have 0.2 for the main view sizes (dark grey), 0.05 within the pairs (black), and 0.1 between the pairs (light grey)
Then simply changing the size of the containing view will cause the views to re-size proportionally:
This is entirely within the storyboard, but you could do the same thing in code.
Note that I'm using only proportions within the StackView to avoid having an incorrect total size, (and making sure they add up to 1.0), but it should be possible to also have some set heights within the StackView if done correctly.
so as you will see below I have a scrollview and I want to add it the the UIViewControllers root view. When I have it constrained to the top, right, bottom, and left I expect to see the red color take up the whole screen. This obviously works, but I want to add a subview to the scrollview that will wrap all the child views. How would I go about doing that?
I have added the view and I have set the same constraints except this time they are set from the wrapper view to the bounds of the UIScrollView, and the blue background color doesn't show anywhere. Also feel free to point out if this is a bad idea, but I thought I could just have it be constrained to the bottom and it will automatically extend the scrollviews content size as needed. This seems to work when I had all the subviews in the scrollview without a wrapper and the last view would extend the content size.
scrollView = UIScrollView(frame: view.bounds)
scrollView?.showsVerticalScrollIndicator = true
scrollView?.backgroundColor = .red
scrollView?.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(scrollView!)
scrollView?.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
scrollView?.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
scrollView?.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
scrollView?.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
//setup wrapper view
let subviewWrapper = UIView()
subviewWrapper.translatesAutoresizingMaskIntoConstraints = false
scrollView?.addSubview(subviewWrapper)
subviewWrapper.backgroundColor = .blue
subviewWrapper.topAnchor.constraint(equalTo: (scrollView?.topAnchor)!).isActive = true
subviewWrapper.leftAnchor.constraint(equalTo: (scrollView?.leftAnchor)!).isActive = true
subviewWrapper.rightAnchor.constraint(equalTo: (scrollView?.rightAnchor)!).isActive = true
subviewWrapper.bottomAnchor.constraint(equalTo: (scrollView?.bottomAnchor)!).isActive = true
Actually this is a very good idea. I always set up my scrollViews this way. I usually call the view contentView, but it is the same idea.
You're almost there. You haven't yet given Auto Layout anything to go on to figure out the size of your subviewWrapper. The constraints you've set so far pin the subviewWrapper to the edges of the scrollView's content area, but this just establishes the fact that as the subviewWrapper grows, the content size of the scrollView will expand. Currently your subviewWrapper has 0 width and 0 height which is why you see no blue.
Below are 3 examples of how you might establish the size of your subviewWrapper.
Note: Each of the following examples is completely independent. Look at each one separately and as you try them, remember to delete the constraints added by the previous example.
Example 1: Make subviewWrapper 1000 x 1000:
Set constraints to make your subviewWrapper 1000 x 1000 and you will see the blue and it will scroll in both directions.
subviewWrapper.widthAnchor.constraint(equalToConstant: 1000).isActive = true
subviewWrapper.heightAnchor.constraint(equalToConstant: 1000).isActive = true
Example 2: Vertical only scrolling with content size 2X of scrollView height:
If you set the width of your subviewWrapper to be equal to the width of the scrollView then it will only scroll vertically. If you set the height of subviewWrapper to 2X the height of scrollView, then your blue area will be twice the height of the scrollView.
subviewWrapper.widthAnchor.constraint(equalTo: scrollView!.widthAnchor, multiplier: 1.0).isActive = true
subviewWrapper.heightAnchor.constraint(equalTo: scrollView!.heightAnchor, multiplier: 2.0).isActive = true
Example 3: Size of subviewWrapper set by its subviews:
You can also establish the size of your subviewWrapper by adding subviews to it that are fully specified in size and connected in a chain from the top of subviewWrapper to the bottom, and from side to side. If you do this, Auto Layout will have enough information to compute the size of your subviewWrapper
In this example, I've added a yellow 600 x 600 square to the subviewWrapper and set it 100 points from each edge. Without having explicitly set a size for subviewWrapper, Auto Layout can figure out that it is 800 x 800.
let yellowSquare = UIView()
yellowSquare.translatesAutoresizingMaskIntoConstraints = false
yellowSquare.backgroundColor = .yellow
subviewWrapper.addSubview(yellowSquare)
yellowSquare.widthAnchor.constraint(equalToConstant: 600).isActive = true
yellowSquare.heightAnchor.constraint(equalToConstant: 600).isActive = true
yellowSquare.topAnchor.constraint(equalTo: subviewWrapper.topAnchor, constant: 100).isActive = true
yellowSquare.leadingAnchor.constraint(equalTo: subviewWrapper.leadingAnchor, constant: 100).isActive = true
yellowSquare.trailingAnchor.constraint(equalTo: subviewWrapper.trailingAnchor, constant: -100).isActive = true
yellowSquare.bottomAnchor.constraint(equalTo: subviewWrapper.bottomAnchor, constant: -100).isActive = true