I need to make an IBDesignable to make a custom navigation bar file that will adjust the height of the view based on the iPhone type. if the iPhone has top notch like iPhone X,XR, then the height contraint will be 88, otherwise for iPhone 8 that does not has top notch, the height will be 64.
I need to set the height contraint, not the layer height. here is the code I use but it fails to update the height contraint
import UIKit
#IBDesignable
class CustomParentNavigationBarView: UIView {
override func awakeFromNib() {
super.awakeFromNib()
self.setHeight()
}
func setHeight() {
let deviceHasTopNotch = checkHasTopNotchOrNot()
var heightConstraint = NSLayoutConstraint()
if deviceHasTopNotch {
heightConstraint = NSLayoutConstraint(item: self, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 88)
} else {
heightConstraint = NSLayoutConstraint(item: self, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 64)
}
heightConstraint.isActive = true
self.addConstraint(heightConstraint)
}
func checkHasTopNotchOrNot() -> Bool {
if #available(iOS 11.0, tvOS 11.0, *) {
// with notch: 44.0 on iPhone X, XS, XS Max, XR.
// without notch: 20.0 on iPhone 8 on iOS 12+.
return UIApplication.shared.delegate?.window??.safeAreaInsets.top ?? 0 > 20
}
return false
}
}
the result should be something like this (red view), the height of the red view should change according to iPhone type, either 88 or 64
for the initial value, I set the autolayout of the view in storyboard like this
There are two problems that I can see.
You are not activating the constraints. Add this line
heightConstraint.isActive = true
You are calling SetHeight multiple times. Each time, a constraint is added. This will lead to constraint conflicts and poor behavior. Instead, just create the constraint once and store it as a member.
I'm trying to load a sub view on to every single page of my app from a nib file. Right now I'm using a somewhat unusual approach to loading this sub view in that I am doing it through an extension of UIStoryboard (probably not relevant to my problem, but I'm not sure). So this is how the code looks when I load the nib file:
extension UIStoryboard {
public func appendCustomView(to viewController: UIViewController) {
if let myCustomSubview = Bundle.main.loadNibNamed("MyCustomSubview", owner: nil, options: nil)![0] as? MyCustomSubview {
viewController.view.addSubview(myCustomSubview)
}
}
}
This code does what it's supposed to do and adds "MyCustomSubview" to the view controller (I won't go in to detail on exactly how this method gets called because it works so it doesn't seem important). The problem is I can't for the life of me figure out how to add constraints that effect the size of myCustomSubview. I have tried putting code in the function I showed above as well as in the MyCustomSubview swift file to add constraints but no matter what I do the subview never changes.
Ideally the constraints would pin "MyCustomSubview" to the bottom of the ViewController, with width set to the size of the screen and a hard coded height constraint.
Here are the two main methods I tried (with about 100 minor variations for each) that did NOT work:
Method 1 - Add constraint directly from "appendCustomView"
public func appendCustomView(to viewController: UIViewController) {
if let myCustomSubview = Bundle.main.loadNibNamed("MyCustomSubview", owner: nil, options: nil)![0] as? MyCustomSubview {
let top = NSLayoutConstraint(item: myCustomSubview, attribute: .top, relatedBy: .equal
, toItem: viewController.view, attribute: .top, multiplier: 1, constant: 50.0)
viewController.view.addSubview(myCustomSubview)
viewController.view.addConstraint(top)
}
}
Method 2 - Add constraint outlets and setter method in MyCustomSubview
class MyCustomSubview: UIView {
#IBOutlet weak var widthConstraint: NSLayoutConstraint!
#IBOutlet weak var heightConstraint: NSLayoutConstraint!
func setConstraints(){
self.widthConstraint.constant = UIScreen.main.bounds.size.width
self.heightConstraint.constant = 20
}
}
And call setter method in "appendCustomView"
public func appendCustomView(to viewController: UIViewController) {
if let myCustomSubview = Bundle.main.loadNibNamed("MyCustomSubview", owner: nil, options: nil)![0] as? MyCustomSubview {
myCustomSubview.setConstraints()
viewController.view.addSubview(myCustomSubview)
}
}
(*note: the actual constraints of these examples are irrelevant and I wasn't trying to meet the specs I mentioned above, I was just trying to make any sort of change to the view to know that the constraints were updating. They weren't.)
Edit : Changed "MyCustomNib" to "MyCustomSubview" for clarity.
When you add constraints onto a view from a Nib, you have to call yourView.translatesAutoresizingMaskIntoConstraints = false, and you also need to make sure that you have all 4 (unless it's a label or a few other view types which only need 2) constraints in place:
Here's some sample code that makes a view fill it's parent view:
parentView.addSubview(yourView)
yourView.translatesAutoresizingMaskIntoConstraints = false
yourView.topAnchor.constraint(equalTo: parentView.topAnchor).isActive = true
yourView.leadingAnchor.constraint(equalTo: parentView.leadingAnchor).isActive = true
yourView.bottomAnchor.constraint(equalTo: parentView.bottomAnchor).isActive = true
yourView.trailingAnchor.constraint(equalTo: parentView.trailingAnchor).isActive = true
Edit: I've actually come around to perferring this method of adding NSLayoutConstraints, even though the results are the same
NSLayoutConstraint.activate([
yourView.topAnchor.constraint(equalTo: parentView.topAnchor),
yourView.leadingAnchor.constraint(equalTo: parentView.leadingAnchor),
yourView.bottomAnchor.constraint(equalTo: parentView.bottomAnchor),
yourView.trailingAnchor.constraint(equalTo: parentView.trailingAnchor),
])
For anyone who comes across this in the future, this is the solution I came up with by tweaking this answer a little bit
Add a setConstraints(withRelationshipTo) method in the swift class that corresponds to the nib file:
class MyCustomSubview: UIView {
func setConstraints(withRelationshipTo view: UIView){
self.translatesAutoresizingMaskIntoConstraints = false
// Replace with your own custom constraints
self.heightAnchor.constraint(equalToConstant: 40.0).isActive = true
self.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
self.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
self.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
}
}
Then call the setConstraints method after you add the nib file to the view (probably in viewWillAppear or viewDidLoad of a view controller )
class MyViewController: UIViewController {
override func viewWillAppear(_ animated: Bool){
super.viewWillAppear(animated)
if let myCustomSubview = Bundle.main.loadNibNamed("MyCustomSubview", owner: nil, options: nil)![0] as? MyCustomSubview {
let view = self.view // Added for clarity
view.addSubview(myCustomSubview)
myCustomSubview.setConstraints(withRelationshipTo: view)
}
}
}
You can use this extension for anywhere you're going to add a subview to a existing UIView.
extension UIView {
func setConstraintsFor(contentView: UIView, left: Bool = true, top: Bool = true, right: Bool = true, bottom: Bool = true) {
contentView.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(contentView)
var constraints : [NSLayoutConstraint] = []
if left {
let constraintLeft = NSLayoutConstraint(item: contentView, attribute: .left, relatedBy: .equal, toItem: self, attribute: .left, multiplier: 1, constant: 0)
constraints.append(constraintLeft)
}
if top {
let constraintTop = NSLayoutConstraint(item: contentView, attribute: .top, relatedBy: .equal, toItem: self, attribute: .top, multiplier: 1, constant: 0)
constraints.append(constraintTop)
}
if right {
let constraintRight = NSLayoutConstraint(item: contentView, attribute: .right, relatedBy: .equal, toItem: self, attribute: .right, multiplier: 1, constant: 0)
constraints.append(constraintRight)
}
if bottom {
let constraintBottom = NSLayoutConstraint(item: contentView, attribute: .bottom, relatedBy: .equal, toItem: self, attribute: .bottom, multiplier: 1, constant: 0)
constraints.append(constraintBottom)
}
self.addConstraints(constraints)
}
}
You can call this method like this:
containerView.setConstraintsFor(contentView: subView!, top: false)
This will add subView to the containerView and constraint to all sides except top side.
You can modify this method to pass left, top, right, bottom Constant value if you want.
TL;DR
My programmatically created table view cells are not resizing according to the intrinsic content height of their custom views, even though I am using UITableViewAutomaticDimension and setting both the top and bottom constraints.
The problem probably lies in my implementation of the UITableViewCell subclass. See the code below under Doesn't work programmatically > Code > MyCustomCell.swift.
Goal
I'm trying to make a suggestion bar for a custom Mongolian keyboard. Mongolian is written vertically. In Android it looks like this:
Progress
I've learned that I should use a UITableView with variable cell heights, which is available starting with iOS 8. This requires using auto layout and telling the table view to use automatic dimensions for the cell heights.
Some things I've had to learn along the way are represented in my recent SO questions and answers:
How to make a custom table view cell
Getting variable height to work with in a table view with a standard UILabel
Getting intrinsic content size to work for a custom view
Using a programmatically created UITableViewCell
Set constraints programmatically
So I have come to the point where I have the vertical labels that support intrinsic content size. These labels go in my custom table view cells. And as described in the next section, they work when I do it in the storyboard, but not when I create everything programmatically.
Works in IB
In order to isolate the problem I created two basic projects: one for where I use the storyboard and one where I do everything programmatically. The storyboard project works. As can be seen in the following image, each table view cell resizes to match the height of custom vertical label.
In IB
I set constraints to pin the top and bottom as well as centering the label.
Code
ViewController.swift
import UIKit
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
let myStrings: [String] = ["a", "bbbbbbb", "cccc", "dddddddddd", "ee"]
let cellReuseIdentifier = "cell"
#IBOutlet var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
tableView.delegate = self
tableView.dataSource = self
tableView.estimatedRowHeight = 44.0
tableView.rowHeight = UITableViewAutomaticDimension
}
// number of rows in table view
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.myStrings.count
}
// create a cell for each table view row
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell:MyCustomCell = self.tableView.dequeueReusableCellWithIdentifier(cellReuseIdentifier) as! MyCustomCell
cell.myCellLabel.text = self.myStrings[indexPath.row]
return cell
}
// method to run when table view cell is tapped
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
print("You tapped cell number \(indexPath.row).")
}
}
MyCustomCell.swift
import UIKit
class MyCustomCell: UITableViewCell {
#IBOutlet weak var myCellLabel: UIMongolSingleLineLabel!
}
Doesn't work programmatically
Since I want the suggestion bar to be a part of the final keyboard, I need to be able to create it programmatically. However, when I try to recreate the above example project programmatically, it isn't working. I get the following result.
The cell heights are not resizing and the custom vertical labels are overlapping each other.
I also get the following error:
Warning once only: Detected a case where constraints ambiguously
suggest a height of zero for a tableview cell's content view. We're
considering the collapse unintentional and using standard height
instead.
This error has been brought up before multiple times on Stack Overflow:
iOS8 - constraints ambiguously suggest a height of zero
Detected a case where constraints ambiguously suggest a height of zero
custom UITableviewcell height not set correctly
ios 8 (UITableViewCell) : Constraints ambiguously suggest a height of zero for a tableview cell's content view
However, the problem for most of those people is that they were not setting both a top and bottom pin constraint. I am, or at least I think I am, as is shown in my code below.
Code
ViewController.swift
import UIKit
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
let myStrings: [String] = ["a", "bbbbbbb", "cccc", "dddddddddd", "ee"]
let cellReuseIdentifier = "cell"
var tableView = UITableView()
override func viewDidLoad() {
super.viewDidLoad()
// Suggestion bar
tableView.frame = CGRect(x: 0, y: 20, width: view.bounds.width, height: view.bounds.height)
tableView.registerClass(MyCustomCell.self, forCellReuseIdentifier: cellReuseIdentifier)
tableView.delegate = self
tableView.dataSource = self
tableView.estimatedRowHeight = 44.0
tableView.rowHeight = UITableViewAutomaticDimension
view.addSubview(tableView)
}
// number of rows in table view
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.myStrings.count
}
// create a cell for each table view row
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell:MyCustomCell = self.tableView.dequeueReusableCellWithIdentifier(cellReuseIdentifier) as! MyCustomCell
cell.myCellLabel.text = self.myStrings[indexPath.row]
return cell
}
// method to run when table view cell is tapped
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
print("You tapped cell number \(indexPath.row).")
}
}
MyCustomCell.swift
I think the problem is probably in here since this is the main difference from the IB project.
import UIKit
class MyCustomCell: UITableViewCell {
var myCellLabel = UIMongolSingleLineLabel()
override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
self.setup()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func setup() {
self.myCellLabel.translatesAutoresizingMaskIntoConstraints = false
self.myCellLabel.centerText = false
self.myCellLabel.backgroundColor = UIColor.yellowColor()
self.addSubview(myCellLabel)
// Constraints
// pin top
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.Top, relatedBy: NSLayoutRelation.Equal, toItem: self.contentView, attribute: NSLayoutAttribute.TopMargin, multiplier: 1.0, constant: 0).active = true
// pin bottom
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.Bottom, relatedBy: NSLayoutRelation.Equal, toItem: self.contentView, attribute: NSLayoutAttribute.BottomMargin, multiplier: 1.0, constant: 0).active = true
// center horizontal
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.contentView, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0).active = true
}
override internal class func requiresConstraintBasedLayout() -> Bool {
return true
}
}
Supplemental Code
I'll also include the code for the custom vertical label that I used in both projects above, but since the IB project works, I don't think the main problem is here.
import UIKit
#IBDesignable
class UIMongolSingleLineLabel: UIView {
private let textLayer = LabelTextLayer()
var useMirroredFont = false
// MARK: Primary input value
#IBInspectable var text: String = "A" {
didSet {
textLayer.displayString = text
updateTextLayerFrame()
}
}
#IBInspectable var fontSize: CGFloat = 17 {
didSet {
updateTextLayerFrame()
}
}
#IBInspectable var centerText: Bool = true {
didSet {
updateTextLayerFrame()
}
}
// MARK: - Initialization
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
required init?(coder: NSCoder) {
super.init(coder: coder)
setup()
}
func setup() {
// Text layer
textLayer.backgroundColor = UIColor.yellowColor().CGColor
textLayer.useMirroredFont = useMirroredFont
textLayer.contentsScale = UIScreen.mainScreen().scale
layer.addSublayer(textLayer)
}
override func intrinsicContentSize() -> CGSize {
return textLayer.frame.size
}
func updateTextLayerFrame() {
let myAttribute = [ NSFontAttributeName: UIFont.systemFontOfSize(fontSize) ]
let attrString = NSMutableAttributedString(string: textLayer.displayString, attributes: myAttribute )
let size = dimensionsForAttributedString(attrString)
// This is the frame for the soon-to-be rotated layer
var x: CGFloat = 0
var y: CGFloat = 0
if layer.bounds.width > size.height {
x = (layer.bounds.width - size.height) / 2
}
if centerText {
y = (layer.bounds.height - size.width) / 2
}
textLayer.frame = CGRect(x: x, y: y, width: size.height, height: size.width)
textLayer.string = attrString
invalidateIntrinsicContentSize()
}
func dimensionsForAttributedString(attrString: NSAttributedString) -> CGSize {
var ascent: CGFloat = 0
var descent: CGFloat = 0
var width: CGFloat = 0
let line: CTLineRef = CTLineCreateWithAttributedString(attrString)
width = CGFloat(CTLineGetTypographicBounds(line, &ascent, &descent, nil))
// make width an even integer for better graphics rendering
width = ceil(width)
if Int(width)%2 == 1 {
width += 1.0
}
return CGSize(width: width, height: ceil(ascent+descent))
}
}
// MARK: - Key Text Layer Class
class LabelTextLayer: CATextLayer {
// set this to false if not using a mirrored font
var useMirroredFont = true
var displayString = ""
override func drawInContext(ctx: CGContext) {
// A frame is passed in, in which the frame size is already rotated at the center but the content is not.
CGContextSaveGState(ctx)
if useMirroredFont {
CGContextRotateCTM(ctx, CGFloat(M_PI_2))
CGContextScaleCTM(ctx, 1.0, -1.0)
} else {
CGContextRotateCTM(ctx, CGFloat(M_PI_2))
CGContextTranslateCTM(ctx, 0, -self.bounds.width)
}
super.drawInContext(ctx)
CGContextRestoreGState(ctx)
}
}
Update
The entire code for the project is all here, so if anyone is interested enough to try it out, just make a new project and cut and paste the code above into the following three files:
ViewController.swift
MyCustomCell.swift
UIMongolSingleLineLabel.swift
The error is pretty trivial:
Instead of
self.addSubview(myCellLabel)
use
self.contentView.addSubview(myCellLabel)
Also, I would replace
// pin top
NSLayoutConstraint(...).active = true
// pin bottom
NSLayoutConstraint(...).active = true
// center horizontal
NSLayoutConstraint(...).active = true
with
let topConstraint = NSLayoutConstraint(...)
let bottomConstraint = NSLayoutConstraint(...)
let centerConstraint = NSLayoutConstraint(...)
self.contentView.addConstraints([topConstraint, bottomConstraint, centerConstraint])
which is more explicit (you have to specify the constraint owner) and thus safer.
The problem is that when calling active = true on a constraint, the layout system has to decide to which view it should add the constraints. In your case, because the first common ancestor of contentView and myCellLabel is your UITableViewCell, they were added to your UITableViewCell, so they were not actually constraining the contentView (constraints were between siblings not between superview-subview).
Your code actually triggered a console warning:
Warning once only: Detected a case where constraints ambiguously suggest a height of zero for a tableview cell's content view. We're considering the collapse unintentional and using standard height instead.
Which made me to look immediately at the way the constraints are created for your label.
I have tested your code and found the issue was in setting constraints please use below code part for setting constants in your "MyCustomCell.swift" file setup() function
let topConstraint = NSLayoutConstraint(item: myCellLabel, attribute: .Top, relatedBy: .Equal, toItem: self, attribute: .Top, multiplier: 1, constant: 0)
let bottomConstraint = NSLayoutConstraint(item: myCellLabel, attribute: .Bottom, relatedBy: .Equal, toItem: self, attribute: .Bottom, multiplier: 1, constant: 0)
let centerConstraint = NSLayoutConstraint(item: myCellLabel, attribute: .CenterX, relatedBy: .Equal, toItem: self, attribute: .CenterX, multiplier: 1, constant: 0)
self.addConstraints([centerConstraint, topConstraint, bottomConstraint])
Also set clips to bound property to your cell lable in "viewcontroller.swift"
// create a cell for each table view row
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell:MyCustomCell = self.tableView.dequeueReusableCellWithIdentifier(cellReuseIdentifier) as! MyCustomCell
cell.myCellLabel.text = self.myStrings[indexPath.row]
cell.myCellLabel.clipsToBounds=true
return cell
}
For your ease I have uploaded my sample code on GitHub Dynamic Height Sample
Output is looking like this now
The problem seems to come from the vertical constraints in the cell
By putting them relative to self instead of self.contentView in MyCustomCell you can fix your problem
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.Top, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.TopMargin, multiplier: 1.0, constant: 0).active = true
// pin bottom
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.Bottom, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.BottomMargin, multiplier: 1.0, constant: 0).active = true
// center horizontal
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0).active = true
the full class would be:
import UIKit
class MyCustomCell: UITableViewCell {
var myCellLabel = UIMongolSingleLineLabel()
override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
self.setup()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func setup() {
self.myCellLabel.translatesAutoresizingMaskIntoConstraints = false
self.myCellLabel.centerText = false
self.myCellLabel.backgroundColor = UIColor.yellowColor()
self.addSubview(myCellLabel)
// Constraints
// pin top
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.Top, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.TopMargin, multiplier: 1.0, constant: 0).active = true
// pin bottom
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.Bottom, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.BottomMargin, multiplier: 1.0, constant: 0).active = true
// center horizontal
NSLayoutConstraint(item: myCellLabel, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0).active = true
}
override internal class func requiresConstraintBasedLayout() -> Bool {
return true
}
}
The thing you are missing is this function:
override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
return heightValue
}
Im not so sure what you should do exactly, but by the fact that you know your labels you should be able to return an exact height value for each cell in this method
I think you are missing to set constraints for tableView with superview. And try to increase estimated row height also.
I am trying to center an arrow button with a width = 40 in the middle of my screen using constraints programmatically.
My code works if I call it in viewDidAppear but crashes in viewDidLoad.
Having it in viewDidAppear is an eye sore since you see the screen and then see the button jump to the middle of the screen. Any idea how to make it set up before the view is shown?
I might add this is a subview so I am calling centerArrow() from a viewController whose view is not the same view.
So inside the viewController:
let pview = NSBundle.mainBundle().loadNibNamed("Profile", owner: nil, options: nil)[0] as! ProfileView
override func viewDidAppear(animated: Bool) {
pview.centerArrow()
}
And inside ProfileView which inherits UIView:
func centerArrow()
{
let screenSize: CGRect = UIScreen.mainScreen().bounds
let width = (screenSize.width / 2) - 20
let constraint = NSLayoutConstraint(item: arrowButton, attribute: NSLayoutAttribute.LeftMargin, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.LeftMargin, multiplier: 1, constant: width)
self.addConstraint(constraint)
}
Try using viewDidLayoutSubViews, that might provide the timing you are looking for in this case.
I'm creating a viewController which contain 2 textViews a title and a fullText. At the moment i've created 2 textViews in the interface builder which is placed below each other and then created following code to change the height to equal to the content. However the issue is that it seem to be delayed, which gives a bad user experience. By delay i mean that it takes 0.5 or 1 sec before it resize? here is my code:
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
setHeightToContent(self.titleText!)
setHeightToContent(self.fullText!)
scrollView?.contentSize = CGSizeMake(self.view.frame.width, self.fullText!.frame.origin.y + self.fullText!.frame.height)
println(self.fullText!.frame.origin.y + self.fullText!.frame.height)
}
func setHeightToContent(theTextView: UITextView) {
let contentSize = theTextView.sizeThatFits(theTextView.bounds.size)
var frame = theTextView.frame
frame.size.height = contentSize.height
theTextView.frame = frame
var aspectRatioTextViewConstraint = NSLayoutConstraint(item: theTextView, attribute: .Height, relatedBy: .Equal, toItem: theTextView, attribute: .Width, multiplier: theTextView.bounds.height/theTextView.bounds.width, constant: 1)
theTextView.addConstraint(aspectRatioTextViewConstraint)
}
Make each of the text views self-sizing in accordance with its own content, and use constraints so that the scroll view's contentSize is configured automatically based on its content.