Related
I'm trying to make a custom tableView cell that has a stackView from an array images.
I used interface builder and added a horizontal stackView with:
Center X
Center Y
Top +12
Bottom +12
I'm using a loop to add Arranged Subview and it works fine. But the images are super small, even though they shouldn't be due to their CGRect. But they are getting adjusted by the stackView.
The idea was to keep the stack centered, while also using the top/bottom to adjust the hight of the cell.
I've reasoned that the issue I'm facing with the images being small is because the stackView is initialized empty. So the stackViews hight is very tiny. And because imageViews are being added inside of it, they are then being resized to fit.
How can you get a cell/stackView to adjust their hight after being displayed?
Note: I've also been having issues with trying to add a top & bottom constraint to the imageView programmatically.
for pictogram in pictograms {
let imageView = UIImageView()
let size = self.bounds.width / CGFloat(pictograms.count + 1)
print("size: ", size)
imageView.frame = CGRect(x: 0, y: 0, width: size, height: size)
imageView.contentMode = .scaleAspectFit
imageView.image = pictogram.image
pictogramStack.addArrangedSubview(imageView)
}
You are using a UIStackView in the wrong way. Stack views will arrange the subviews for you - no need to be calculating widths and setting frames.
Layout your cell prototype like this:
Note that the Bottom constraint has Priority: 999. Auto-layout needs to make multiple "passes" to lay out stack views (particularly in table view cells). Using a priority of 999 for the bottom constraint will avoid Constraint Conflict error / warning messages.
Set the stack view properties like this:
With Distribution: Fill Equally we don't have to do any let size = self.bounds.width / CGFloat(pictograms.count + 1) kind of calculations.
Also, to make design-time a little easier, give the stack view a Placeholder intrinsic height:
That will have no effect at run-time, but allows you to clearly see your cell elements at design time.
Now, when you "fill" the stack view with image views, no .frame = setting, and the only constraint you need to add is Height == Width:
NSLayoutConstraint.activate([
// image view should have 1:1 ratio
imageView.heightAnchor.constraint(equalTo: imageView.widthAnchor),
])
Here is a complete example:
class HorizontalImagesStackCell: UITableViewCell {
#IBOutlet var theStack: UIStackView!
func addImages(_ pictograms: [String]) -> Void {
// cells are reused, so remove any previously added image views
theStack.arrangedSubviews.forEach {
$0.removeFromSuperview()
}
pictograms.forEach { s in
// make sure we can load the image
if let img = UIImage(named: s) {
// instantiate an image view
let imageView = UIImageView()
// give it a background color so we can see its frame
imageView.backgroundColor = .green
// scale aspect fit
imageView.contentMode = .scaleAspectFit
// set the image
imageView.image = img
NSLayoutConstraint.activate([
// image view should have 1:1 ratio
imageView.heightAnchor.constraint(equalTo: imageView.widthAnchor),
])
// add it to the stack
theStack.addArrangedSubview(imageView)
}
}
}
}
class ImagesInStackTableViewController: UITableViewController {
// we'll display 5 rows of images
// going from 5 images to 4 images ... to 1 image
let myData: [Int] = [5, 4, 3, 2, 1]
let myImages: [String] = [
"img1", "img2", "img3", "img4", "img5"
]
override func viewDidLoad() {
super.viewDidLoad()
}
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return myData.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "HCell", for: indexPath) as! HorizontalImagesStackCell
// get the first n number of images
let a: [String] = Array(myImages.prefix(myData[indexPath.row]))
cell.addImages(a)
return cell
}
}
Using these 5 images:
We get this result (image views are set to .scaleAspectFit and have green backgrounds so we can see the frames):
I need to update constraints (height of my CollectionView) when request is done and I have images from server, so height of View also will change.
Result screen
what I need screen
My code:
DispatchQueue.main.async {
self.cvActivity.alpha = 0
self.collectionView.reloadData()
self.collectionView.heightAnchor.constraint(equalToConstant: self.cellWidth * 2).isActive = true
self.collectionView.setNeedsUpdateConstraints()
self.collectionView.setNeedsLayout()
self.view.layoutIfNeeded()
}
Well, basic idea by #J. Doe is correct, here some code explanation (for simplicity i used UIView, not UICollectionView):
import UIKit
class ViewController: UIViewController {
#IBOutlet var heightConstraint: NSLayoutConstraint! // link the height constraint to your collectionView
private var height: CGFloat = 100 // you should keep constraint height for different view states somewhere
override func updateViewConstraints() {
heightConstraint.constant = height // set the correct height
super.updateViewConstraints()
}
// update height by button press with animation
#IBAction func increaseHight(_ sender: UIButton) {
height *= 2
UIView.animate(withDuration: 0.3) {
self.view.setNeedsUpdateConstraints()
self.view.layoutIfNeeded() // if you call `layoutIfNeeded` on your collectionView, animation doesn't work
}
}
}
Result:
Define a height for your collectionView, create an outlet from that constraint and increase the constant of that constraint and call layoutifneeded in an animation block
You need to make object of your Height constraint from storyboard
#IBOutlet weak var YourHeightConstraintName: NSLayoutConstraint!
YourConstraintName.constant = valueYouWantToGive
---------OR--------
collectionViewOutlet.view.frame = CGRect(x:
collectionViewOutlet.frame.origin.x , y:
collectionViewOutlet.frame.origin.y, width:
collectionViewOutlet.frame.width, height:
yourheightValue)
I would like the UICollectionView (The red one) to shrink to the height of the content size in this case UICollectionViewCells(the yellow ones) because there is a lot of empty space. What I tried is to use:
override func layoutSubviews() {
super.layoutSubviews()
if !__CGSizeEqualToSize(bounds.size, self.intrinsicContentSize) {
self.invalidateIntrinsicContentSize()
}
}
override var intrinsicContentSize: CGSize {
return self.collection.contentSize
}
but return self.collection.contentSize always return (width, 0)
and for this reason it shrinks too much to value of height 30 (The value which I set in the XIB file for the height, although I have constaint >= 30).
I would suggest the following:
Add a height constraint to your collection view.
Set its priority to 999.
Set its constant to any value that makes it reasonably visible on the storyboard.
Change the bottom equal constraint of the collection view to greater or equal.
Connect the height constraint to an outlet.
Every time you reload the data on the collection view do the following:
You may also want to consider the Inset of the collection view by adding it to the content size.
Code Sample:
CGFloat height = myCollectionView.collectionViewLayout.collectionViewContentSize.height
heightConstraint.constant = height
self.view.setNeedsLayout() Or self.view.layoutIfNeeded()
Explanation: Extra, You don't have to read if you understand it. obviously!!
The UI will try to reflect all the constraints no matter what are their priorities. Since there is a height constraint with lower priority of (999), and a bottom constraint of type greater or equal. whenever, the height constraint constant is set to a value less than the parent view height the collection view will be equal to the given height, achieving both constraints.
But, when the height constraint constant set to a value more than the parent view height both constraints can't be achieved. Therefore, only the constraint with the higher priority will be achieved which is the greater or equal bottom constraint.
The following is just a guess from an experience. So, it achieves one constrant. But, it also tries to make the error in the resulted UI for the other un-achieved lower priority constraint as lowest as possible. Therefore, the collection view height will be equal to the parent view size.
In Swift 5 and Xcode 10.2.1
My CollectionView name is myCollectionView
Fix height for your CollectionView
Create Outlet for your CollectionViewHeight
IBOutlet weak var myCollectionViewHeight: NSLayoutConstraint!
Use below code
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
let height = myCollectionView.collectionViewLayout.collectionViewContentSize.height
myCollectionViewHeight.constant = height
self.view.layoutIfNeeded()
}
Dynamic width for cell based on text content...
Dynamic cell width of UICollectionView depending on label width
1) Set Fix Height of your CollectionView.
2) Create Outlet of this CollectionView Height Constant.
Like :
IBOutlet NSLayoutConstraint *constHeight;
3) Add below method in your .m file:
- (void)viewDidLayoutSubviews {
[super viewDidLayoutSubviews];
CGFloat height = collectionMenu.collectionViewLayout.collectionViewContentSize.height;
constHeight.constant = height;
}
I ended up, by subclassing the UICollectionView and overriding some methods as follows.
Returning self.collectionViewLayout.collectionViewContentSize for intrinsicContentSize makes sure, to always have the correct size
Then just call it whenever it might change (like on reloadData)
Code:
override func reloadData() {
super.reloadData()
self.invalidateIntrinsicContentSize()
}
override var intrinsicContentSize: CGSize {
return self.collectionViewLayout.collectionViewContentSize
}
But be aware, that you lose "cell re-using", if you display large sets of data, eventhough they don't fit on the screen.
This seemed like the simplest solution for me.
class SelfSizingCollectionView: UICollectionView {
override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
super.init(frame: frame, collectionViewLayout: layout)
commonInit()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonInit()
}
private func commonInit() {
isScrollEnabled = false
}
override var contentSize: CGSize {
didSet {
invalidateIntrinsicContentSize()
}
}
override func reloadData() {
super.reloadData()
self.invalidateIntrinsicContentSize()
}
override var intrinsicContentSize: CGSize {
return contentSize
}
}
You may not need to override reloadData
You have to set height constraint as equal to content size
HeightConstraint.constant = collection.contentSize.height
Took the solution by d4Rk which is great, except in my case it would keep cutting off the bottom of my collection view (too short). I figured out this was because intrinsic content size was sometimes 0 and this would throw off the calculations. IDK. All I know is this fixed it.
import UIKit
class SelfSizedCollectionView: UICollectionView {
override func reloadData() {
super.reloadData()
self.invalidateIntrinsicContentSize()
}
override var intrinsicContentSize: CGSize {
let s = self.collectionViewLayout.collectionViewContentSize
return CGSize(width: max(s.width, 1), height: max(s.height,1))
}
}
Subclass UICollectionView as follows
Delete height constraint if any
Turn on Intrinsic Size
-
class ContentSizedCollectionView: UICollectionView {
override var contentSize:CGSize {
didSet {
invalidateIntrinsicContentSize()
}
}
override var intrinsicContentSize: CGSize {
layoutIfNeeded()
return CGSize(width: UIView.noIntrinsicMetric, height: collectionViewLayout.collectionViewContentSize.height)
}
}
If you set the height constraint of the collection view. Just observe the contentSize change in the viewDidLoad and update the constraint.
self.contentSizeObservation = collectionView.observe(\.contentSize, options: [.initial, .new]) { [weak self] collectionView, change in
guard let `self` = self else { return }
guard self.collectionView.contentSize != .zero else { return }
self.collectionViewHeightLayoutConstraint.constant = self.collectionView.contentSize.height
}
I have a multi-line, multi-selection UICollectionView subclass where the cells are of fixed height and left-aligned flowing from left to right. It's embedded in a vertical stack view that's inside a vertical scroll view. See the UI component below the label "Property Types".
In order for the collection view to fit the height of its contentSize, here's what I had to do (note that this is all within the UICollectionView subclass):
Give the collection view a non-zero minimum height constraint of priority 999. Auto-sizing the collection view to its content height simply won't work with zero height.
let minimumHeight = heightAnchor.constraint(greaterThanOrEqualToConstant: 1)
minimumHeight.priority = UILayoutPriority(999)
minimumHeight.isActive = true
Set the collection view's content hugging priority to .required for the vertical axis.
setContentHuggingPriority(.required, for: .vertical)
Calling reloadData() is followed by the following calls:
invalidateIntrinsicContentSize()
setNeedsLayout()
layoutIfNeeded()
For example, I have a setItems() function in my subclass:
func setItems(_ items: [Item]) {
self.items = items
selectedIndices = []
reloadData()
invalidateIntrinsicContentSize()
setNeedsLayout()
layoutIfNeeded()
}
Override contentSize and intrinsicContentSize as follows:
override var intrinsicContentSize: CGSize {
return contentSize
}
override var contentSize: CGSize {
didSet {
invalidateIntrinsicContentSize()
setNeedsLayout()
layoutIfNeeded()
}
}
Do following.
first set height constrain for UICollectionView
here calendarBaseViewHeight is UICollectionView height Variable
call the function after reload the collection view
func resizeCollectionViewSize(){
calendarBaseViewHeight.constant = collectionView.contentSize.height
}
first of all calculate number of cells than multiply it with height of cell and then return height in this method
collectionView.frame = CGRectMake (x,y,w,collectionView.collectionViewLayout.collectionViewContentSize.height); //objective c
//[collectionView reloadData];
collectionView.frame = CGRect(x: 0, y: 0, width: width, height: collectionView.collectionViewLayout.collectionViewContentSize.height) // swift
On your UICollectionView set your constraints such as Trailing, Leading, and Bottom:
If you look at my height constraint in more detail, as it is purely for storyboard look so I don't get errors, I have it to Remove at build time. The real height constraint is set in my code down below.
My code for DrawerCollectionView, which is set as the collection view Custom Class:
import UIKit
class DrawerCollectionView: UICollectionView {
override func didMoveToSuperview() {
super.didMoveToSuperview()
heightAnchor.constraint(equalToConstant: contentSize.height).isActive = true
}
}
Adjusting height of UICollectionView to the height of it's content size 🙌🏻
SWIFT 5
final class MyViewController: UIViewController {
// it's important to declare layout as separate constant due to late update in viewDidLayoutSubviews()
private let layout = UICollectionViewFlowLayout()
private lazy var collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
override func viewDidLoad() {
super.viewDidLoad()
setupCollectionView()
setupCollectionViewConstraints()
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
updateFlowLayout()
}
private func setupCollectionView() {
view.addSubview(collectionView)
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "UICollectionViewCell")
collectionView.dataSource = self
}
private func setupCollectionViewConstraints() {
// your collectionView constraints setup
}
private func updateFlowLayout() {
let height = collectionView.collectionViewLayout.collectionViewContentSize.height
layout.itemSize = CGSize(width: view.frame.width, height: height)
layout.scrollDirection = .horizontal
layout.minimumInteritemSpacing = .zero
layout.minimumLineSpacing = .zero
layout.sectionInset = UIEdgeInsets.zero
}
}
extension MyViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {...}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {...}
}
work for me
let heightRes = resCollectionView.collectionViewLayout.collectionViewContentSize.height
foodHeightConstrant.constant = height.advanced(by: 1 )
foodCollectionView.setNeedsLayout()
foodCollectionView.layoutIfNeeded()
I was using a UICollectionView in UITableView cell. For me, the following solution worked.
In parent view of collection view, I updated the height constraint in layoutSubviews method like this
override func layoutSubviews() {
heightConstraint.constant = myCollectionView.collectionViewLayout.collectionViewContentSize.height
}
and then in cellForRowAtIndexpath, just before returning the cell, call this
cell.layoutIfNeeded()
The only solution worked for me when CollectionView is inside TableView custom cell is to
Subclass from ContentSizedCollectionView:
final class ContentSizedCollectionView: UICollectionView {
override var contentSize: CGSize{
didSet {
if oldValue.height != self.contentSize.height {
invalidateIntrinsicContentSize()
}
}
}
override var intrinsicContentSize: CGSize {
return CGSize(width: UIView.noIntrinsicMetric,
height: contentSize.height)
}
}
private let collectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .vertical
layout.sectionInset = UIEdgeInsets(top: 20, left: 17, bottom: 20, right: 17)
let collectionView = ContentSizedCollectionView(frame: .zero, collectionViewLayout: layout).prepareForAutoLayout()
return collectionView
}()
In UITableViewDelegate for TableView cell:
if let reusableCell = cell as? YourTableViewCell {
reusableCell.frame = tableView.bounds
reusableCell.layoutIfNeeded()
}
Remove height constraints of UICollectionView if any.
This article helped me a lot: https://medium.com/#ar.sarris/self-sizing-collectionview-inside-a-tableview-f1fd4f42c44d
Get the height of the cell. Something like this
let cellHeight = cell.frame.height
Get the origin of the collection view
let cvOrigin = collectionView.frame.origin
Get the width of the collection view
let cvWidth = collectionView.bounds.width
Set the frame of the content view
collection.frame = CGRect(x: cvOrigin.x, y: cvOrigin.y, width: cvWidth, height: cellHeight )
I have a simple project with a storyboard containing only a single a UICollectionViewController, built with Xcode 7.1.1 for iOS 9.1
class ViewController: UICollectionViewController {
var values = ["tortile", "jetty", "tisane", "glaucia", "formic", "agile", "eider", "rooter", "nowhence", "hydrus", "outdo", "godsend", "tinkler", "lipscomb", "hamlet", "unbreeched", "fischer", "beastings", "bravely", "bosky", "ridgefield", "sunfast", "karol", "loudmouth", "liam", "zunyite", "kneepad", "ashburn", "lowness", "wencher", "bedwards", "guaira", "afeared", "hermon", "dormered", "uhde", "rusher", "allyou", "potluck", "campshed", "reeda", "bayonne", "preclose", "luncheon", "untombed", "northern", "gjukung", "bratticed", "zeugma", "raker"]
#IBOutlet weak var flowLayout: UICollectionViewFlowLayout!
override func viewDidLoad() {
super.viewDidLoad()
flowLayout.estimatedItemSize = CGSize(width: 10, height: 10)
}
override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return values.count
}
override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("MyCell", forIndexPath: indexPath) as! MyCell
cell.name = values[indexPath.row]
return cell
}
override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
values.removeAtIndex(indexPath.row)
collectionView.deleteItemsAtIndexPaths([indexPath])
}
}
class MyCell: UICollectionViewCell {
#IBOutlet weak var label: UILabel!
var name: String? {
didSet {
label.text = name
}
}
}
When deleting the cells from the collection view, all remaining cells animate to their estimatedItemSize, and then swap back to the correct size.
Interestingly, this produces auto layout constraint warnings for each cell when the animation occurs:
2015-12-02 14:30:45.236 CollectionTest[1631:427853] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x14556f780 h=--& v=--& H:[UIView:0x1456ac6c0(10)]>",
"<NSLayoutConstraint:0x1456acfd0 UIView:0x1456ac6c0.trailingMargin == UILabel:0x1456ac830'raker'.trailing>",
"<NSLayoutConstraint:0x1456ad020 UILabel:0x1456ac830'raker'.leading == UIView:0x1456ac6c0.leadingMargin>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1456acfd0 UIView:0x1456ac6c0.trailingMargin == UILabel:0x1456ac830'raker'.trailing>
My initial thought was that breaking these constraints was what was causing the resizing problem.
Updating the cell's awakeFromNib method:
override func awakeFromNib() {
super.awakeFromNib()
contentView.translatesAutoresizingMaskIntoConstraints = false
}
fixes the warnings, but the problem still occurs.
I tried re-adding my own constraints between the cell and its contentView, but this didn't resolve the issue:
override func awakeFromNib() {
super.awakeFromNib()
contentView.translatesAutoresizingMaskIntoConstraints = false
for constraint in [
contentView.leadingAnchor.constraintEqualToAnchor(leadingAnchor),
contentView.trailingAnchor.constraintEqualToAnchor(trailingAnchor),
contentView.topAnchor.constraintEqualToAnchor(topAnchor),
contentView.bottomAnchor.constraintEqualToAnchor(bottomAnchor)]
{
constraint.priority = 999
constraint.active = true
}
}
Thoughts?
flow layout calculates actual sizes of cells after doing layout by estimated sizes to define which ones are visible. After that it adjusts the layout based on real sizes.
However, when it animates, when it calculates initial position for animation, it doesn't reach the stage of dequeueing cells and running auto layout there, so it uses only estimated sizes.
The easiest way is to try to give the closest estimated sizes, or if you could provide the size in the delegate in sizeForItemAt call.
In my case, I was trying to animate layoutAttributes without inserting or deleting cells and for that specific case I subclassed UICollectionViewFlowLayout and then overridden this method:
override func invalidateLayout(with context: UICollectionViewLayoutInvalidationContext) {
if !context.invalidateEverything && context.invalidatedItemIndexPaths == nil && context.contentOffsetAdjustment == .zero && context.contentSizeAdjustment == .zero {
return
}
super.invalidateLayout(with: context)
}
This prevents recalculating layout attributes using estimated sizes when nothing has been changed.
TL;DR: I could only get a collection view to properly behave with the delegate sizeForItem method. Working sample here: https://github.com/chrisco314/CollectionView-AutoLayout
In the controller:
func collectionView(_ collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAt indexPath: IndexPath) -> CGSize {
var cell = Cell.prototype
let contents = data[indexPath.section][indexPath.item]
cell.text = contents
cell.expand = selected.contains(indexPath)
let width = collectionView.bounds
.inset(collectionView.contentInset)
.inset(layout.sectionInset)
.width
let finalSize = cell.systemLayoutSizeFitting(
.init(width: width, height: 0),
withHorizontalFittingPriority: .required,
verticalFittingPriority: .fittingSizeLevel)
.withWidth(width)
print("sizeForItemAt: \(finalSize)")
return finalSize
}
In the cell:
override func systemLayoutSizeFitting(
_ targetSize: CGSize,
withHorizontalFittingPriority horizontalFittingPriority: UILayoutPriority,
verticalFittingPriority: UILayoutPriority) -> CGSize {
let contentSize = contentView.systemLayoutSizeFitting(
targetSize,
withHorizontalFittingPriority: horizontalFittingPriority,
verticalFittingPriority: verticalFittingPriority)
return contentSize
}
Constraints for an expanding panel:
lazy var panel: UIView = {
let view = Panel()
view.pin(body, to: .left, .top, .right)
view.clipsToBounds = true
panelHeight = view.heightAnchor.constraint(equalTo: body.heightAnchor)
return view
}()
var panelHeight: NSLayoutConstraint!
lazy var height:CGFloat = 60
lazy var body: UIView = {
let view = Body()
view.backgroundColor = .blue
view.pin(contents, inset: 9)
let bodyHeight = view.heightAnchor.constraint(equalToConstant: height)
bodyHeight.isActive = true
return view
}()
lazy var contents: UILabel = {
let label = UILabel()
label.backgroundColor = .white
label.numberOfLines = 0
label.text = "Body with height constraint of \(height)"
return label
}()
I had a host of problems like this and many others, spent a stupid amount of time trying to find a path through that worked for all cases - rendering with autolayout, rational animations for insertion and deletion, handling rotations, etc. In my experience, the only way that worked was to use the sizeForItem delegate method. You can use estimatedSize and auto layout, but for me, the animations would always collapse to the top, and everything then spring down again - perhaps what you are seeing.
I have a sample that is basically my playground for testing. I tried different approaches across the different tabs of the tab view controller here, using estimated sizes, constraints on the cells themselves, custom systemSizeFitting that returns the desired size, and the delegate based sizeThatFits
The sample is a bit hacked up, but the third tab demonstrates a delegate based method that works for expanding cells, and insertion and deletion animations. Note that tab2? demonstrates inconsistent animations that the collection view uses, based on the ratio of expanding cells. If the ratio is greater than 2:1, it fades and snaps, if it is less then 2:1, it animates up and down smoothly.
All the non delegate approaches that tried failed when it came to animations, per above. Maybe there is an approach that works without the delegate method (and I would love to see if it it did), but I could not find it.
If you like to try the source code (which you are very welcome to do), have a look at my Bitbucket repository.
I have a popover dialogue that shows a list of settings. These settings a listed inside multiple UITableViews. The UITableViews shall not be scrollable, for the overall settings view already is. Furthermore, the popover dialogue shall take as much screen vertically as it needs but shall be horizontally compressed.
Thus, I conceived the following structure:
UIView => MySettingsViewController
- UIScrollView
- UIView (Content View)
- Container View1
- UITableView (embedded) => MyTableViewController
- Container View2
- UITableView (embedded)
The structure is assembled via Interface Builder and Autolayout is used for the sizing.
I have both the Scroll View, the Content View (I started with just one) and the Container View to their respective superviews (or layout guides). I constrained the size of the content view in the following manner:
contentView.width == (topmost) UIView.width
contentView.height == 200 // removed at build time
Additionally, I set the size of the table view to its content size, because otherwise the popover appears to be empty:
class MyTableViewController: UITableViewController {
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
// this is Cartography syntax - the intention should be clear
layout(view, replace: ConstraintGroup()) { [unowned self] view in
view.width == self.tableView.contentSize.width
view.height == self.tableView.contentSize.height
}
view.setNeedsLayout()
}
}
The settings popover is filled with content, but its size is not quite right:
To fix this, I tried the following approach which does not work:
class MySettingsViewController: UIViewController {
override var preferredContentSize: CGSize {
get {
let compressedSize = view.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize)
// this is always (0, 0) because the subviews are not resized, yet
return compressedSize
}
set {
super.preferredContentSize = newValue
}
}
}
To conclude: The compression does not work.
So I just fixed the problem myself as you can see when looking at the Bitbucket repository.
The layout is now fixed both in MyTableViewController and MySettingsViewController. The former one now looks like this:
class MyTableViewController: UITableViewController {
var heightConstraint: NSLayoutConstraint?
var tableViewEdgesConstraints: [NSLayoutConstraint]?
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
if let container = tableView.superview where tableViewEdgesConstraints == nil {
layout(tableView, container, replace: ConstraintGroup()) { [unowned self] tableView, container in
self.tableViewEdgesConstraints = tableView.edges == inset(container.edges, 0)
}
}
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
if let heightConstraint = heightConstraint {
if Int(heightConstraint.constant) != Int(tableView.contentSize.height) {
heightConstraint.constant = self.tableView.contentSize.height
}
} else {
layout(view, replace: ConstraintGroup()) { [unowned self] view in
if (self.tableView.contentSize.height > 0) {
self.heightConstraint = view.height == self.tableView.contentSize.height
}
}
}
}
}
So basically, I constraint the height of the table to its content's height and change the constraint if the content's height changes. This is done as soon as the table is laid out. Furthermore, the nested table view is pinned by its edges to the edges of the container view. I think that this is mandatory because I could not find out how to constrain two views of different scenes right in Interface Builder.
In MySettingsViewController the scrollview's size is set to the size of the content view's frame (which is accessible via an outlet) as soon as this size is known. Furthermore, to make the popover compress, the preferredContentSize of the settings controller is adapted accordingly, when the height changes (if you omit the condition you might get yourself in a layout endless loop. Furthermore I did 3 things to make it possible to have a navigation controller wrapped around MySettingsViewController:
The width of the popover is set to a fixed value (otherwise it would sometimes expand to the full width).
The presentedViewController's preferredContentSize needs to be set equally.
I had to set the insets of the scrollView to 0 to avoid an ugly vertical offset - this solution is sub-optimal because it breaks the scroll view experience a bit. But it works.
Here is the code:
class MySettingsViewController: UIViewController {
#IBOutlet weak var contentView: UIView!
#IBOutlet weak var scrollView: UIScrollView!
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
scrollView.contentSize = contentView.frame.size
if (preferredContentSize.height != scrollView.contentSize.height) {
let newSize = CGSize(width: 400, height: scrollView.contentSize.height)
preferredContentSize = newSize
presentingViewController?.presentedViewController?.preferredContentSize = newSize
scrollView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0)
}
}
}
And this is the result: