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AutoSizing cells: cell width equal to the CollectionView
(2 answers)
Closed 3 years ago.
I'm working on a rebuild of UI on mobile App. I've changed my tableView by CollectionView (for have two columns of cells)
I've achieve the work to have dynamic heigh on cell and that work perfectly, as you can see (iOS left and Android right) I'm trying to achieve the android UI with iOS.
Currently that what I have follow to achieve that :
https://www.vadimbulavin.com/collection-view-cells-self-sizing/
I've trying to set fixed width but that's automatically shape to the content.
I think that probably a little thing but I havent work from long time on iOS, so I'm looking for explain to achieve the fixed width size
The controller contain only that :
#IBOutlet weak var collectionViewFlowLayout: UICollectionViewFlowLayout!{
didSet {
self.collectionViewFlowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
}
}
I havent do the 'max width' part of tutorial.
All label inside cell have left right constraint fixed, 0 lines and word wrap line break
Thank !
Have a nice day
Benjamin
Well, as i see from screenshot, you already have auto height on each cell.
Set fixed width for CollectionViewCell:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
var height:CGFloat = 0.0
if let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
height = layout.itemSize.height
}
let screenSize = UIScreen.main
let wi = screenSize.bounds.size.width/2 // can calculate gap between two columns
return CGSize(width: wi, height: height)
}
You need to do a custom layout of class UICollectionViewLayout and set it to your collection view. There are a lot of Pinterest like collection view tutorials. You can check this
I found the next answer to make UIView's height match its content https://stackoverflow.com/a/39527226/7767664
I tested it, it works fine (if UIView height size in storyboard bigger or smaller than its content then during runtime it autoresize itself to match the content).
But if I use UICollectionViewCell instead of UIView then nothing changes, height of cell is never changed, it always has the hardcoded height we have in storyboard properties:
What else can I do?
Also I have 2 sections in UIControllerView (2 columns).
Two cells in one row should have the same size even if their size content is different (something like this implemented in Android natively when using RecyclerView with GridLayoutManager, very easy)
Update
It works with UIView because I set its top constraint to Safe Are'a top
I can't do it with UICollectionViewCell
Update 2
It seems I have some progress with this answer https://stackoverflow.com/a/25896386/7767664
But instead of newFrame.size.width = CGFloat(ceilf(Float(size.width))) I need newFrame.size.height = CGFloat(ceilf(Float(size.height)))
and when we use this solution, don't add any constraints to cell's bottom otherwise it will not work
With this solution I can't really use any margins otherwise some part of becomes invisible at the bottom of cell
I guess it can be solved with this question https://stackoverflow.com/a/31279726/7767664
You can try with this function called inside you collectionView Extension or inside your native collectionViewController class:
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize
{
//return something like the size. I write you an example how to use it.
// You can easily change the value according to your stuff contents height.
return CGSize(width: collectionView.frame.size.width/3, height: 100)
}
I solved my issue thanks to https://stackoverflow.com/a/25896386/7767664 and https://stackoverflow.com/a/31279726/7767664
I decided to put one UIView with all needed child views inside it to UICollecitonViewCell
I set UIView trailing, leading, top to ICollecitonViewCell but I didn't set bottom to cell view (you should use the latest child view inside UIView and connect their bottoms, not with the cell view)
Then I added reference of UIView to my custom cell class and I use its height for cell's height:
public class MyCustomItemCell: UICollectionViewCell {
// other child views references ...
#IBOutlet weak var wrapperView: UIView! // view which contains your other views
//forces the system to do one layout pass
var isHeightCalculated: Bool = false
override public func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
//Exhibit A - We need to cache our calculation to prevent a crash.
if !isHeightCalculated {
setNeedsLayout()
layoutIfNeeded()
var newFrame = layoutAttributes.frame
newFrame.size.height = wrapperView.frame.height // use height of our UIView
layoutAttributes.frame = newFrame
isHeightCalculated = true
}
return layoutAttributes
}
}
I don't know why it is so complicated to design cells that can adapt to its content. It shouldn't need that much code, I still don't understand why UIKit can't handle this properly.
Anyway, here is my issue (I have edited the whole post):
I have an UICollectionViewCell that contains an UITableView.
Here is my sizeForItem method :
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAt indexPath: IndexPath) -> CGSize {
var cellWidth: CGFloat = collectionView.bounds.size.width
var cellHeight: CGFloat = 0
let cellConfigurator = items[indexPath.item].cellConfigurator
if type(of: cellConfigurator).reuseId == "MoonCollectionViewCell" {
if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: type(of: cellConfigurator).reuseId, for: indexPath) as? MoonCollectionViewCell {
cell.contentView.layoutIfNeeded()
let size = cell.selfSizedTableView.intrinsicContentSize
cellHeight = size.height
}
}
return CGSize.init(width: cellWidth, height: cellHeight)
}
sizeForItem is called before cellForItem, that's the reason of the layoutIfNeeded, because I couldn't get the correct intrinsic content size.
I have removed the XIB as suggested, and designed my UICollectionViewCell within the Storyboard.
Here is my UICollectionViewCell designed within a Storyboard (only the UITableViewCell is designed in a XIB file)
I only added an UITableView within the UICollectionViewCell.
I want the UICollectionViewCell to adapt its size according to the height of the tableView.
Now here is my tableView :
I have created a subclass of UITableView (from this post)
class SelfSizedTableView: UITableView {
var maxHeight: CGFloat = UIScreen.main.bounds.size.height
override func reloadData() {
super.reloadData()
self.invalidateIntrinsicContentSize()
self.layoutIfNeeded()
}
override var intrinsicContentSize: CGSize {
let height = min(contentSize.height, maxHeight)
return CGSize(width: contentSize.width, height: height)
}
}
Please note that I have disabled scrolling, I have dynamic prototype for the tableView cells, the style is grouped.
EDIT : Check the configure method, it comes from a protocol I used to configure in a generic way all my UICollectionViewCell
func configure(data: [MoonImages]) {
selfSizedTableView.register(UINib.init(nibName: "MoonTableViewCell", bundle: nil), forCellReuseIdentifier: "MoonTableViewCell")
selfSizedTableView.delegate = self
selfSizedTableView.dataSource = moonDataSource
var frame = CGRect.zero
frame.size.height = .leastNormalMagnitude
selfSizedTableView.tableHeaderView = UIView(frame: frame)
selfSizedTableView.tableFooterView = UIView(frame: frame)
selfSizedTableView.maxHeight = 240.0
selfSizedTableView.estimatedRowHeight = 40.0
selfSizedTableView.rowHeight = UITableView.automaticDimension
moonDataSource.data.addAndNotify(observer: self) { [weak self] in
self?.selfSizedTableView.reloadData()
}
moonDataSource.data.value = data
}
FYI the dataSource is a custom dataSource, with dynamic value (Generics) and the observer pattern, to reload the collection/tableView when the data is set.
I also have this warning when I launch the App.
[CollectionView] An attempt to update layout information was detected
while already in the process of computing the layout (i.e. reentrant
call). This will result in unexpected behaviour or a crash. This may
happen if a layout pass is triggered while calling out to a delegate.
Any hints or advice on how I should handle this ?
Because I am facing a strange behavior, it's like my sizeForItem use random values. The UICollectionViewCell height is not the same than my UITableView intrinsic content size height.
If I have 2 rows within my UITableView, the UICollectionView is not always equal at this size. I really don't know how to achieve this...
Should I invalideLayout?
Maybe it's not the answer you wanted, but here're my two cents. For your particular requirements, the better solution is moving away from UITableView, and use UIStackView or your custom container view.
Here's why:
UITableView is a subclass of UIScrollView, but since you've disabled its scrolling feature, you don't need a UIScrollView.
UITableView is mainly used to reuse cells, to improve performance and make code more structured. But since you're making it as large as its content size, none of your cells are reused, so features of UITableView is not taken any advantage of.
Thus, actually you don't need and you should not use either UITableView or UIScrollView inside the UICollectionViewCell for your requirements.
If you agree with above part, here're some learnings from our practices:
We always move most of the underlying views and code logics, mainly data assembling, into a UIView based custom view, instead of putting in UITableViewCell or UICollectionViewCell directly. Then add it to UITableViewCell or UICollectionViewCell's contentView and setup constraints. With this structure, we can reuse our custom view in more scenarios.
For requirements similar to yours, we'll create a factory class to create "rows" similar to how you create "cells" for your UITableView, add them into a vertical UIStackView, create constraints deciding UIStackView's width. Auto layout will take care of the rest things.
In your usage with UICollectionViewCell, to calculate the wanted height, inside preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) func of your cell, you can use contentView.systemLayoutSizeFitting(targetSize, withHorizontalFittingPriority: .required, verticalFittingPriority: .fittingSizeLevel) to calculate the height, do some check and return. Also, remember to invalidate layout when the width of the UICollectionView changes.
It is indeed very tricky, but I found a working way to solve this problem. As far as i know i got this from a chat app, where message bubble sizes are dynamic.
Here we go:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAt indexPath: IndexPath) -> CGSize {
// Minimum size
let frame = CGRect(x: 0, y: 0, width: view.frame.width - 30, height: 0)
let cell = MoonCollectionViewCell()
// Fill it with the content it will have in the actual cell,
// cell.content is just an example
let cell.content = items[indexPath.item]
cell.layoutIfNeeded()
// Define the maximum size it can be
let targetSize = CGSize(width: view.frame.width - 30, height: 240)
let estimatedSize = cell.systemLayoutSizeFittingSize(tagetSize)
return CGSize(width: view.frame.width - 30, height: estimatedSize.height)
}
What it basically do is, to define a minimum frame and the size that is targeted. Then by calling systemLayoutSizeFittingSize, it resizes the cell to the optimal size, but not larger than the targetSize.
Adjust the code to your needs, but this should work.
I tried to find the culprit in the posted code, but it seems that there are many moving parts. So, I will try to give some hints, that hopefully could help.
In theory (there is caveat for iOS 12), self sizing UICollectionViewCells should not be difficult. You essentially could set the collectionViewLayout.estimedItemSize to any value (preferred is the constant below), like this:
(collectionView.collectionViewLayout as? UICollectionViewFlowLayout)?.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
Then you have to make sure the constraints in the cells are set in a way that it can self size; that is auto layout can calculate the width and the height of the cell. You are providing an intrinsicContentSize of the tableView and it is wrapped by its super view from all four ends, so this should be OK.
Once you set the estimatedItemSize as shown above, you should not implement the delegate method returning the size:
func collectionView(_: UICollectionView, layout: UICollectionViewLayout, sizeForItemAt: IndexPath) -> CGSize
A quick tutorial can be found here for further reference: https://medium.com/#wasinwiwongsak/uicollectionview-with-autosizing-cell-using-autolayout-in-ios-9-10-84ab5cdf35a2
As I said in theory it should not be difficult, but cell auto sizing seems broken on iOS 12 see here In iOS 12, when does the UICollectionView layout cells, use autolayout in nib
If I were in you position, I would start from afresh, adding complexity step by step:
try implement the self sizing cells, possibly with with a simple UIView and an override of intrinsicContentSize; possibly by using iOS 11.4 SDK to exclude issues relevant to iOS 12 (the easiest way is to download latest Xcode 9 and work from there); if not possible do the iOS 12 fixes at this step
replace the simple view with a table view (which may also have dynamic sizing per see)
do the tableview reload data flow, i.e. dynamic sizing feature
if everything OK, do the iOS 12 fixes and migrate to iOS 12
Hope this helps.
BTW, the warning in the console is probably due to call to layoutIfNeeded() in the delegate method. It triggers an immediate layout pass, whereas this is done for the UICollectionView once all sizes are collected.
I need to have a view controller that has a scroll in view.
The problem is that I need that both scrolls (of scrollView and collectionView) work together.
But when I add ScrollView in all frame, nothing works...
That's an image that shows what I want:
And when I scroll viewController, all content scroll together..
Someone know a good way to implement this in swift 4?
Thanks in advance.
I've seen this done many ways. The most popular of which is to have these views embedded in a UITableView.
You can set the first cell height to a proportional amount to the superview, while keeping another cell that will contain your CollectionView. You would be able to take advantage of the UITableView's scrollView as well as it's memory efficiency and delegate.
A better way to do this is to use the scroll direction in UICollectionViewDelagateFlowLayout. Just add the UICollectionViewDelegateFlowLayout protocol or extends your ViewController to it. Then use .scrollDirection in the section of your UICollectionView.
And sample declaration like this
let collectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
...
layout.scrollDirection = .vertical //or .horizontal depends on your liking
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
...//
return cv
}()
then add to your view view.addSubview(collectionView)
More info in the apple doc or jump to definition
I'm trying to get self sizing UICollectionViewCells working with Auto Layout, but I can't seem to get the cells to size themselves to the content. I'm having trouble understanding how the cell's size is updated from the contents of what's inside the cell's contentView.
Here's the setup I've tried:
Custom UICollectionViewCell with a UITextView in its contentView.
Scrolling for the UITextView is disabled.
The contentView's horizontal constraint is: "H:|[_textView(320)]", i.e. the UITextView is pinned to the left of the cell with an explicit width of 320.
The contentView's vertical constraint is: "V:|-0-[_textView]", i.e. the UITextView pinned to the top of the cell.
The UITextView has a height constraint set to a constant which the UITextView reports will fit the text.
Here's what it looks like with the cell background set to red, and the UITextView background set to Blue:
I put the project that I've been playing with on GitHub here.
This answer is outdated from iOS 14 with the addition of compositional layouts. Please consider updating the new API
Updated for Swift 5
preferredLayoutAttributesFittingAttributes renamed to preferredLayoutAttributesFitting and use auto sizing
Updated for Swift 4
systemLayoutSizeFittingSize renamed to systemLayoutSizeFitting
Updated for iOS 9
After seeing my GitHub solution break under iOS 9 I finally got the time to investigate the issue fully. I have now updated the repo to include several examples of different configurations for self sizing cells. My conclusion is that self sizing cells are great in theory but messy in practice. A word of caution when proceeding with self sizing cells.
TL;DR
Check out my GitHub project
Self sizing cells are only supported with flow layout so make sure thats what you are using.
There are two things you need to setup for self sizing cells to work.
#1. Set estimatedItemSize on UICollectionViewFlowLayout
Flow layout will become dynamic in nature once you set the estimatedItemSize property.
self.flowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
#2. Add support for sizing on your cell subclass
This comes in 2 flavours; Auto-Layout or custom override of preferredLayoutAttributesFittingAttributes.
Create and configure cells with Auto Layout
I won't go to in to detail about this as there's a brilliant SO post about configuring constraints for a cell. Just be wary that Xcode 6 broke a bunch of stuff with iOS 7 so, if you support iOS 7, you will need to do stuff like ensure the autoresizingMask is set on the cell's contentView and that the contentView's bounds is set as the cell's bounds when the cell is loaded (i.e. awakeFromNib).
Things you do need to be aware of is that your cell needs to be more seriously constrained than a Table View Cell. For instance, if you want your width to be dynamic then your cell needs a height constraint. Likewise, if you want the height to be dynamic then you will need a width constraint to your cell.
Implement preferredLayoutAttributesFittingAttributes in your custom cell
When this function is called your view has already been configured with content (i.e. cellForItem has been called). Assuming your constraints have been appropriately set you could have an implementation like this:
//forces the system to do one layout pass
var isHeightCalculated: Bool = false
override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
//Exhibit A - We need to cache our calculation to prevent a crash.
if !isHeightCalculated {
setNeedsLayout()
layoutIfNeeded()
let size = contentView.systemLayoutSizeFitting(layoutAttributes.size)
var newFrame = layoutAttributes.frame
newFrame.size.width = CGFloat(ceilf(Float(size.width)))
layoutAttributes.frame = newFrame
isHeightCalculated = true
}
return layoutAttributes
}
NOTE On iOS 9 the behaviour changed a bit that could cause crashes on your implementation if you are not careful (See more here). When you implement preferredLayoutAttributesFittingAttributes you need to ensure that you only change the frame of your layout attributes once. If you don't do this the layout will call your implementation indefinitely and eventually crash. One solution is to cache the calculated size in your cell and invalidate this anytime you reuse the cell or change its content as I have done with the isHeightCalculated property.
Experience your layout
At this point you should have 'functioning' dynamic cells in your collectionView. I haven't yet found the out-of-the box solution sufficient during my tests so feel free to comment if you have. It still feels like UITableView wins the battle for dynamic sizing IMHO.
##Caveats
Be very mindful that if you are using prototype cells to calculate the estimatedItemSize - this will break if your XIB uses size classes. The reason for this is that when you load your cell from a XIB its size class will be configured with Undefined. This will only be broken on iOS 8 and up since on iOS 7 the size class will be loaded based on the device (iPad = Regular-Any, iPhone = Compact-Any). You can either set the estimatedItemSize without loading the XIB, or you can load the cell from the XIB, add it to the collectionView (this will set the traitCollection), perform the layout, and then remove it from the superview. Alternatively you could also make your cell override the traitCollection getter and return the appropriate traits. It's up to you.
In iOS10 there is new constant called UICollectionViewFlowLayout.automaticSize (formerly UICollectionViewFlowLayoutAutomaticSize), so instead:
self.flowLayout.estimatedItemSize = CGSize(width: 100, height: 100)
you can use this:
self.flowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
It has better performance especially when cells in your collection view have constant width.
Accessing Flow Layout:
override func viewDidLoad() {
super.viewDidLoad()
if let flowLayout = collectionView?.collectionViewLayout as? UICollectionViewFlowLayout {
flowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
}
}
Swift 5 Updated:
override func viewDidLoad() {
super.viewDidLoad()
if let flowLayout = collectionView?.collectionViewLayout as? UICollectionViewFlowLayout {
flowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
}
}
A few key changes to Daniel Galasko's answer fixed all my problems. Unfortunately, I don't have enough reputation to comment directly (yet).
In step 1, when using Auto Layout, simply add a single parent UIView to the cell. EVERYTHING inside the cell must be a subview of the parent. That answered all of my problems. While Xcode adds this for UITableViewCells automatically, it doesn't (but it should) for UICollectionViewCells. According to the docs:
To configure the appearance of your cell, add the views needed to present the data item’s content as subviews to the view in the contentView property. Do not directly add subviews to the cell itself.
Then skip step 3 entirely. It isn't needed.
In iOS 10+ this is a very simple 2 step process.
Ensure that all your cell contents are placed within a single UIView (or inside a descendant of UIView like UIStackView which simplifies autolayout a lot). Just like with dynamically resizing UITableViewCells, the whole view hierarchy needs to have constraints configured, from the outermost container to the innermost view. That includes constraints between the UICollectionViewCell and the immediate childview
Instruct the flowlayout of your UICollectionView to size automatically
yourFlowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
Add flowLayout on viewDidLoad()
override func viewDidLoad() {
super.viewDidLoad()
if let flowLayout = infoCollection.collectionViewLayout as? UICollectionViewFlowLayout {
flowLayout.estimatedItemSize = CGSize(width: 1, height:1)
}
}
Also, set an UIView as mainContainer for your cell and add all required views inside it.
Refer to this awesome, mind-blowing tutorial for further reference:
UICollectionView with autosizing cell using autolayout in iOS 9 & 10
EDIT 11/19/19: For iOS 13, just use UICollectionViewCompositionalLayout with estimated heights. Don't waste your time dealing with this broken API.
After struggling with this for some time, I noticed that resizing does not work for UITextViews if you don't disable scrolling:
let textView = UITextView()
textView.scrollEnabled = false
contentView anchor mystery:
In one bizarre case this
contentView.translatesAutoresizingMaskIntoConstraints = false
would not work. Added four explicit anchors to the contentView and it worked.
class AnnoyingCell: UICollectionViewCell {
#IBOutlet var word: UILabel!
override init(frame: CGRect) {
super.init(frame: frame); common() }
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder); common() }
private func common() {
contentView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
contentView.leftAnchor.constraint(equalTo: leftAnchor),
contentView.rightAnchor.constraint(equalTo: rightAnchor),
contentView.topAnchor.constraint(equalTo: topAnchor),
contentView.bottomAnchor.constraint(equalTo: bottomAnchor)
])
}
}
and as usual
estimatedItemSize = UICollectionViewFlowLayout.automaticSize
in YourLayout: UICollectionViewFlowLayout
Who knows? Might help someone.
Credit
https://www.vadimbulavin.com/collection-view-cells-self-sizing/
stumbled on to the tip there - never saw it anywhere else in all the 1000s articles on this.
I did a dynamic cell height of collection view. Here is git hub repo.
And, dig out why preferredLayoutAttributesFittingAttributes is called more than once. Actually, it will be called at least 3 times.
The console log picture :
1st preferredLayoutAttributesFittingAttributes:
(lldb) po layoutAttributes
<UICollectionViewLayoutAttributes: 0x7fa405c290e0> index path: (<NSIndexPath: 0xc000000000000016>
{length = 2, path = 0 - 0}); frame = (15 12; 384 57.5);
(lldb) po self.collectionView
<UICollectionView: 0x7fa40606c800; frame = (0 57.6667; 384 0);
The layoutAttributes.frame.size.height is current status 57.5.
2nd preferredLayoutAttributesFittingAttributes:
(lldb) po layoutAttributes
<UICollectionViewLayoutAttributes: 0x7fa405c16370> index path: (<NSIndexPath: 0xc000000000000016>
{length = 2, path = 0 - 0}); frame = (15 12; 384 534.5);
(lldb) po self.collectionView
<UICollectionView: 0x7fa40606c800; frame = (0 57.6667; 384 0);
The cell frame height changed to 534.5 as our expected. But, the collection view still zero height.
3rd preferredLayoutAttributesFittingAttributes:
(lldb) po layoutAttributes
<UICollectionViewLayoutAttributes: 0x7fa403d516a0> index path: (<NSIndexPath: 0xc000000000000016>
{length = 2, path = 0 - 0}); frame = (15 12; 384 534.5);
(lldb) po self.collectionView
<UICollectionView: 0x7fa40606c800; frame = (0 57.6667; 384 477);
You can see the collection view height was changed from 0 to 477.
The behavior is similar to handle scroll:
1. Before self-sizing cell
2. Validated self-sizing cell again after other cells recalculated.
3. Did changed self-sizing cell
At beginning, I thought this method only call once. So I coded as the following:
CGRect frame = layoutAttributes.frame;
frame.size.height = frame.size.height + self.collectionView.contentSize.height;
UICollectionViewLayoutAttributes* newAttributes = [layoutAttributes copy];
newAttributes.frame = frame;
return newAttributes;
This line:
frame.size.height = frame.size.height + self.collectionView.contentSize.height;
will cause system call infinite loop and App crash.
Any size changed, it will validate all cells' preferredLayoutAttributesFittingAttributes again and again until every cells' positions (i.e frames) are no more change.
In addition to above answers,
Just make sure you set estimatedItemSize property of UICollectionViewFlowLayout to some size and do not implement sizeForItem:atIndexPath delegate method.
That's it.
The solution comprises 3 simple steps:
Enabling dynamic cell sizing
flowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
Set the containerView.widthAnchor.constraint from collectionView(:cellForItemAt:)to limit the width of contentView to width of collectionView.
class ViewController: UIViewController, UICollectionViewDataSource {
...
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! MultiLineCell
cell.textView.text = dummyTextMessages[indexPath.row]
cell.maxWidth = collectionView.frame.width
return cell
}
...
}
class MultiLineCell: UICollectionViewCell{
....
var maxWidth: CGFloat? {
didSet {
guard let maxWidth = maxWidth else {
return
}
containerViewWidthAnchor.constant = maxWidth
containerViewWidthAnchor.isActive = true
}
}
....
}
Since you want to enable self-sizing of UITextView, it has an additional step to;
3. Calculate and set the heightAnchor.constant of UITextView.
So, whenever the width of contentView is set we'll adjust height of UITextView along in didSet of maxWidth.
Inside UICollectionViewCell:
var maxWidth: CGFloat? {
didSet {
guard let maxWidth = maxWidth else {
return
}
containerViewWidthAnchor.constant = maxWidth
containerViewWidthAnchor.isActive = true
let sizeToFitIn = CGSize(width: maxWidth, height: CGFloat(MAXFLOAT))
let newSize = self.textView.sizeThatFits(sizeToFitIn)
self.textViewHeightContraint.constant = newSize.height
}
}
These steps will get you the desired result.
Complete runnable gist
Reference: Vadim Bulavin blog post - Collection View Cells Self-Sizing: Step by Step Tutorial
Screenshot:
If you implement UICollectionViewDelegateFlowLayout method:
- (CGSize)collectionView:(UICollectionView*)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath*)indexPath
When you call collectionview performBatchUpdates:completion:, the size height will use sizeForItemAtIndexPath instead of
preferredLayoutAttributesFittingAttributes.
The rendering process of performBatchUpdates:completion will go through the method preferredLayoutAttributesFittingAttributes but it ignores your changes.
To whomever it may help,
I had that nasty crash if estimatedItemSize was set. Even if I returned 0 in numberOfItemsInSection. Therefore, the cells themselves and their auto-layout were not the cause of the crash... The collectionView just crashed, even when empty, just because estimatedItemSize was set for self-sizing.
In my case I reorganized my project, from a controller containing a collectionView to a collectionViewController, and it worked.
Go figure.
For anyone who tried everything without luck, this is the only thing that got it working for me.
For the multiline labels inside cell, try adding this magic line:
label.preferredMaxLayoutWidth = 200
More info: here
Cheers!
The example method above does not compile. Here is a corrected version (but untested as to whether or not it works.)
override func preferredLayoutAttributesFittingAttributes(layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes
{
let attr: UICollectionViewLayoutAttributes = layoutAttributes.copy() as! UICollectionViewLayoutAttributes
var newFrame = attr.frame
self.frame = newFrame
self.setNeedsLayout()
self.layoutIfNeeded()
let desiredHeight: CGFloat = self.contentView.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize).height
newFrame.size.height = desiredHeight
attr.frame = newFrame
return attr
}
Update more information:
If you use flowLayout.estimatedItemSize, suggest use iOS8.3 later version. Before iOS8.3, it will crash [super layoutAttributesForElementsInRect:rect];.
The error message is
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'
Second, in iOS8.x version, flowLayout.estimatedItemSize will cause different section inset setting did not work. i.e. function: (UIEdgeInsets)collectionView:layout:insetForSectionAtIndex:.
I tried using estimatedItemSize but there were a bunch of bugs when inserting and deleting cells if the estimatedItemSize was not exactly equal to the cell's height. i stopped setting estimatedItemSize and implemented dynamic cell's by using a prototype cell. here's how that's done:
create this protocol:
protocol SizeableCollectionViewCell {
func fittedSize(forConstrainedSize size: CGSize)->CGSize
}
implement this protocol in your custom UICollectionViewCell:
class YourCustomCollectionViewCell: UICollectionViewCell, SizeableCollectionViewCell {
#IBOutlet private var mTitle: UILabel!
#IBOutlet private var mDescription: UILabel!
#IBOutlet private var mContentView: UIView!
#IBOutlet private var mTitleTopConstraint: NSLayoutConstraint!
#IBOutlet private var mDesciptionBottomConstraint: NSLayoutConstraint!
func fittedSize(forConstrainedSize size: CGSize)->CGSize {
let fittedSize: CGSize!
//if height is greatest value, then it's dynamic, so it must be calculated
if size.height == CGFLoat.greatestFiniteMagnitude {
var height: CGFloat = 0
/*now here's where you want to add all the heights up of your views.
apple provides a method called sizeThatFits(size:), but it's not
implemented by default; except for some concrete subclasses such
as UILabel, UIButton, etc. search to see if the classes you use implement
it. here's how it would be used:
*/
height += mTitle.sizeThatFits(size).height
height += mDescription.sizeThatFits(size).height
height += mCustomView.sizeThatFits(size).height //you'll have to implement this in your custom view
//anything that takes up height in the cell has to be included, including top/bottom margin constraints
height += mTitleTopConstraint.constant
height += mDescriptionBottomConstraint.constant
fittedSize = CGSize(width: size.width, height: height)
}
//else width is greatest value, if not, you did something wrong
else {
//do the same thing that's done for height but with width, remember to include leading/trailing margins in calculations
}
return fittedSize
}
}
now make your controller conform to UICollectionViewDelegateFlowLayout, and in it, have this field:
class YourViewController: UIViewController, UICollectionViewDelegateFlowLayout {
private var mCustomCellPrototype = UINib(nibName: <name of the nib file for your custom collectionviewcell>, bundle: nil).instantiate(withOwner: nil, options: nil).first as! SizeableCollectionViewCell
}
it will be used as a prototype cell to bind data to and then determine how that data affected the dimension that you want to be dynamic
finally, the UICollectionViewDelegateFlowLayout's collectionView(:layout:sizeForItemAt:) has to be implemented:
class YourViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
private var mDataSource: [CustomModel]
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath)->CGSize {
//bind the prototype cell with the data that corresponds to this index path
mCustomCellPrototype.bind(model: mDataSource[indexPath.row]) //this is the same method you would use to reconfigure the cells that you dequeue in collectionView(:cellForItemAt:). i'm calling it bind
//define the dimension you want constrained
let width = UIScreen.main.bounds.size.width - 20 //the width you want your cells to be
let height = CGFloat.greatestFiniteMagnitude //height has the greatest finite magnitude, so in this code, that means it will be dynamic
let constrainedSize = CGSize(width: width, height: height)
//determine the size the cell will be given this data and return it
return mCustomCellPrototype.fittedSize(forConstrainedSize: constrainedSize)
}
}
and that's it. Returning the cell's size in collectionView(:layout:sizeForItemAt:) in this way preventing me from having to use estimatedItemSize, and inserting and deleting cells works perfectly.
In Swift 5, it works for me.
UICollectionViewFlowLayout:
estimatedItemSize = UICollectionViewFlowLayout.automaticSize
UICollectionViewCell:
(ps: I'm using SnapKit)
class Cell: UICollectionViewCell {
let customizedContentView = UIView()
...
func layoutAction() {
contentView.translatesAutoresizingMaskIntoConstraints = false
contentView.addSubview(customizedContentView)
customizedContentView.snp.makeConstraints { make in
make.edges.equalToSuperview()
}
}
}
then you just need to expand customizedContentView.