I have the following subview that I would like to centered in horizontally on the screen and set the vertical distance manually.
let customImageView = AnimationView(name: "image")
customImageView.frame = CGRect(x: -140, y: 40, width: 700, height: 700)
customImageView.contentMode = .scaleAspectFill
self.view.addSubview(customImageView)
Is it possible to ensure that the vertical distance set will account if the screen size of the phone is smaller.
This sounds like a job for Auto Layout (https://developer.apple.com/library/archive/documentation/UserExperience/Conceptual/AutolayoutPG/index.html), which is Apple's constraint-based system made specifically to dynamically size views in relation to other views and screen sizes. In your case, you could set a greater than/less than to constraint to the top of the view and your subview, so that it will be at least a certain amount of spacing with the option to grow if the screen is larger/smaller.
If you would like to still do frame based layouts (e.g. creating a CGRect/frame), you'll have to do the math yourself based on the view.frame.size.height value. Be aware that a view controller's view frame might not be set before viewDidLayoutSubviews is called.
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.
When I rotate the device with a UICollectionView I get an error:
the item height must be less than the height of the UICollectionView minus the section insets top and bottom values, minus the content insets top and bottom values.
I think that this mistake is within my UICollectionViewDelegateFlowLayout where I try to set the height
if UIApplication.shared.statusBarOrientation.isLandscape {
height = min( Constants.screenWidth, Constants.screenHeight )
}
return CGSize(width: view.bounds.width, height: (height - 300) / 1 )
as you can see I've tried to alter the height for the orientation, but ultimately this does not change as I thought it should.
Complete code is in this GitHub link: https://github.com/stevencurtis/CollectionViewRotate
I want to stop getting this error, and ultimately because the height is incorrectly set when I rotate the device the image is larger than the bounds of the view.
How can I set up my flow layout so this doesn't happen.
The height of the screen is irrelevant. What you really care about is the height of the collectionView.
Use:
let height = collectionView.bounds.height
By using that value, the height will be correct when you rotate the phone without your having to check for it explicitly. You'll still want to adjust for insets if you have any.
You should also use collectionView.bounds.width for the width in place of view.bounds.width.
The UIButton in the scrollView is visible, but not accessible. I am using Constraints.
My UI structure is this:
- UIView
- scrollView: UIScrollView
- contentView: UIView
- UIButton
- UIButton
- UIButton
- ....
- UIButton
I've already tried to set the contentSize of the scrollView. And the height of the contentView. Next to that I've tried to uncheck the checkbox Adjust Scroll View Insets in the storyboard of that ViewController without any luck. I've also set the priority of the Align Center Y to 250, and the priority bottom space to 250 of the contentView.
func updateScrollViewSize() {
var contentRect = CGRect.zero
for view in contentView.subviews {
contentRect = contentRect.union(view.frame)
}
contentRect.size = CGSize(width: scrollView.contentSize.width, height: contentRect.height + 50)
scrollView.contentSize = contentRect.size
contentView.frame.size = contentRect.size
contentView.layoutIfNeeded()
}
The button I try to reach has a Y value of: 1030.0
The height of the contentView is: 871.0
Step-by-step:
Add a scroll view to your view, background color red, constrain it 20-pts on each side:
Add a UIView as your "content view" to the scroll view (green background to make it easy to see), constrain it 0-pts on each side, constrain equal width and equal height to the scroll view. Important: change the Priority of the Height constraint to 250!
Add a UILabel to the contentView, constrain it 30-pts from the top, centered horizontally:
Add another label to the contentView, constrain it 300-pts from the first label, centered horizontally:
Add a UIButton to the contentView, constrain it 30-pts from the bottom, centered horizontally:
Now add a vertical constraint from the bottom of the second label to the top of the button, and set it to 400-pts:
As you see, this pushes the button off-screen past the bottom of the scroll view.
Run the app. You will be able to scroll down to see the button, and you'll be able to tap it.
Absolutely no code needed!
If you use AutoLayout, you don't needed to install frames manually.
You can try install constraints properly and content size will be right in this case and you won't have to install content size manually.
If you achieve this, I guess everything will work correctly.
You can follow this or this guide
I have an image view that gets a dynamic image, and uses aspect fit to determine the frame of the image itself. I am trying to constraint a view inside of the image view, but when the image dynamically resizes, the view inside of it doesn't also dynamically resize when my constraints are just set to the borders of the image view.
Is there any way to set the constraint to the content size that the image is after it resizes, inside interface builder?
Thank you!
When you set the image view’s frame, pick an initial height or width—not both. Then, get image.size and calculate the proportional other dimension. For example:
let width = 100
let height = width * image.size.width / image.size.height *
imageView.frame.size = CGSize(width: width, height: height)
imageView.contentMode = .scaleAspectFit
imageView.image = image
Now your imageView is exactly the size of your image. You can do the same thing with a fixed height by simply replacing “height” with “width” and vice versa in the code above.
Hope this is what you’re looking for.
I am trying to reproduce natively the TVML template that provides a grid of clickable images that extends beyond the screen's bounds. I am using a scroll view for this attempt, but I am unable to select elements that are added to the scroll view, but outside its visible area.
The sketch code using buttons for simplicity is as follows:
let dim = 50
for i in 0..<10 {
for j in 0..<10 {
let frame = CGRect(x: i * (dim + 10), y: j * (dim + 10), width: dim, height: dim)
let button = UIButton(type: .System)
button.frame = frame
myScrollView.panGestureRecognizer.allowedTouchTypes = [UITouchType.Indirect.rawValue]
myScrollView.addSubview(button)
}
}
The scroll view is sized such that only half of these buttons are visible. Why is the scroll view not scrolling to the buttons outside this area (using Siri remote)?
I thought the panGesture touchType might help, but it didn't.
Am I missing something obvious?
Set contentSize property to your scrollview. Make sure all components comes under given content size.
myScrollView.contentSize = CGSizeMake(1880, 2000)
It would actually be way easier to just use a UICollectionView. If you add an image to each cell, you'll get exactly the behavior you want after adjusting the collection view to what you want.
This tutorial kind of explains how it works. http://www.brianjcoleman.com/tutorial-collection-views-using-flow-layout/