UICollectionView inside a UITableViewCell -- dynamic height?

Question

One of our application screens requires us to place a UICollectionView inside of a UITableViewCell. This UICollectionView will have a dynamic number of items, resulting in a height which must be calculated dynamically as well. However, I am running into problems trying to calculate the height of the embedded UICollectionView.

Our overarching UIViewController was created in Storyboards and does make use of auto layout. But, I don't know how to dynamically increase the height of the UITableViewCell based on the height of the UICollectionView.

Can anyone give some tips or advice on how to accomplish this?

Answer 1

The right answer is YES, you CAN do this.

I came across this problem some weeks ago. It is actually easier than you may think. Put your cells into NIBs (or storyboards) and pin them to let auto layout do all the work

Given the following structure:

TableView

TableViewCell

CollectionView

CollectionViewCell

CollectionViewCell

CollectionViewCell

[...variable number of cells or different cell sizes]

The solution is to tell auto layout to compute first the collectionViewCell sizes, then the collection view contentSize, and use it as the size of your cell. This is the UIView method that "does the magic":

-(void)systemLayoutSizeFittingSize:(CGSize)targetSize 
     withHorizontalFittingPriority:(UILayoutPriority)horizontalFittingPriority 
           verticalFittingPriority:(UILayoutPriority)verticalFittingPriority

You have to set here the size of the TableViewCell, which in your case is the CollectionView's contentSize.

CollectionViewCell

At the CollectionViewCell you have to tell the cell to layout each time you change the model (e.g.: you set a UILabel with a text, then the cell has to be layout again).

- (void)bindWithModel:(id)model {
    // Do whatever you may need to bind with your data and 
    // tell the collection view cell's contentView to resize
    [self.contentView setNeedsLayout];
}
// Other stuff here...

TableViewCell

The TableViewCell does the magic. It has an outlet to your collectionView, enables the auto layout for collectionView cells using estimatedItemSize of the UICollectionViewFlowLayout.

Then, the trick is to set your tableView cell's size at the systemLayoutSizeFittingSize... method. (NOTE: iOS8 or later)

NOTE: I tried to use the delegate cell's height method of the tableView -(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath.but it's too late for the auto layout system to compute the CollectionView contentSize and sometimes you may find wrong resized cells.

@implementation TableCell

- (void)awakeFromNib {
    [super awakeFromNib];
    UICollectionViewFlowLayout *flow = (UICollectionViewFlowLayout *)self.collectionView.collectionViewLayout;

    // Configure the collectionView
    flow.minimumInteritemSpacing = ...;

    // This enables the magic of auto layout. 
    // Setting estimatedItemSize different to CGSizeZero 
    // on flow Layout enables auto layout for collectionView cells.
    // https://developer.apple.com/videos/play/wwdc2014-226/
    flow.estimatedItemSize = CGSizeMake(1, 1);

    // Disable the scroll on your collection view
    // to avoid running into multiple scroll issues.
    [self.collectionView setScrollEnabled:NO];
}

- (void)bindWithModel:(id)model {
    // Do your stuff here to configure the tableViewCell
    // Tell the cell to redraw its contentView        
    [self.contentView layoutIfNeeded];
}

// THIS IS THE MOST IMPORTANT METHOD
//
// This method tells the auto layout
// You cannot calculate the collectionView content size in any other place, 
// because you run into race condition issues.
// NOTE: Works for iOS 8 or later
- (CGSize)systemLayoutSizeFittingSize:(CGSize)targetSize withHorizontalFittingPriority:(UILayoutPriority)horizontalFittingPriority verticalFittingPriority:(UILayoutPriority)verticalFittingPriority {

    // With autolayout enabled on collection view's cells we need to force a collection view relayout with the shown size (width)
    self.collectionView.frame = CGRectMake(0, 0, targetSize.width, MAXFLOAT);
    [self.collectionView layoutIfNeeded];

    // If the cell's size has to be exactly the content 
    // Size of the collection View, just return the
    // collectionViewLayout's collectionViewContentSize.

    return [self.collectionView.collectionViewLayout collectionViewContentSize];
}

// Other stuff here...

@end

TableViewController

Remember to enable the auto layout system for the tableView cells at your TableViewController:

- (void)viewDidLoad {
    [super viewDidLoad];

    // Enable automatic row auto layout calculations        
    self.tableView.rowHeight = UITableViewAutomaticDimension;
    // Set the estimatedRowHeight to a non-0 value to enable auto layout.
    self.tableView.estimatedRowHeight = 10;

}

CREDIT: @rbarbera helped to sort this out

Answer 2

I think my solution is much simpler than the one proposed by @PabloRomeu.

Step 1. Create outlet from UICollectionView to UITableViewCell subclass, where UICollectionView is placed. Let, it's name will be collectionView

Step 2. Add in IB for UICollectionView height constraint and create outlet to UITableViewCell subclass too. Let, it's name will be collectionViewHeight.

Step 3. In tableView:cellForRowAtIndexPath: add code:

// deque a cell
cell.frame = tableView.bounds;
[cell layoutIfNeeded];
[cell.collectionView reloadData];
cell.collectionViewHeight.constant = cell.collectionView.collectionViewLayout.collectionViewContentSize.height;

Answer 3

Both table views and collection views are UIScrollView subclasses and thus don't like to be embedded inside another scroll view as they try to calculate content sizes, reuse cells, etc.

I recommend you to use only a collection view for all your purposes.

You can divide it in sections and "treat" some sections' layout as a table view and others as a collection view. After all there's nothing you can't achieve with a collection view that you can with a table view.

If you have a basic grid layout for your collection view "parts" you can also use regular table cells to handle them. Still if you don't need iOS 5 support you should better use collection views.

Answer 4

Pablo Romeu's answer above (https://stackoverflow.com/a/33364092/2704206) helped me immensely with my issue. I had to do a few things differently, however, to get this working for my problem. First off, I didn't have to call layoutIfNeeded() as often. I only had to call it on the collectionView in the systemLayoutSizeFitting function.

Secondly, I had auto layout constraints on my collection view in the table view cell to give it some padding. So I had to subtract the leading and trailing margins from the targetSize.width when setting the collectionView.frame's width. I also had to add the top and bottom margins to the return value CGSize height.

To get these constraint constants, I had the option of either creating outlets to the constraints, hard-coding their constants, or looking them up by an identifier. I decided to go with the third option to make my custom table view cell class easily reusable. In the end, this was everything I needed to get it working:

class CollectionTableViewCell: UITableViewCell {

    // MARK: -
    // MARK: Properties
    @IBOutlet weak var collectionView: UICollectionView! {
        didSet {
            collectionViewLayout?.estimatedItemSize = CGSize(width: 1, height: 1)
            selectionStyle = .none
        }
    }

    var collectionViewLayout: UICollectionViewFlowLayout? {
        return collectionView.collectionViewLayout as? UICollectionViewFlowLayout
    }

    // MARK: -
    // MARK: UIView functions
    override func systemLayoutSizeFitting(_ targetSize: CGSize, withHorizontalFittingPriority horizontalFittingPriority: UILayoutPriority, verticalFittingPriority: UILayoutPriority) -> CGSize {
        collectionView.layoutIfNeeded()

        let topConstraintConstant = contentView.constraint(byIdentifier: "topAnchor")?.constant ?? 0
        let bottomConstraintConstant = contentView.constraint(byIdentifier: "bottomAnchor")?.constant ?? 0
        let trailingConstraintConstant = contentView.constraint(byIdentifier: "trailingAnchor")?.constant ?? 0
        let leadingConstraintConstant = contentView.constraint(byIdentifier: "leadingAnchor")?.constant ?? 0

        collectionView.frame = CGRect(x: 0, y: 0, width: targetSize.width - trailingConstraintConstant - leadingConstraintConstant, height: 1)

        let size = collectionView.collectionViewLayout.collectionViewContentSize
        let newSize = CGSize(width: size.width, height: size.height + topConstraintConstant + bottomConstraintConstant)
        return newSize
    }
}

As a helper function to retrieve a constraint by identifier, I add the following extension:

extension UIView {
    func constraint(byIdentifier identifier: String) -> NSLayoutConstraint? {
        return constraints.first(where: { $0.identifier == identifier })
    }
}

NOTE: You will need to set the identifier on these constraints in your storyboard, or wherever they are being created. Unless they have a 0 constant, then it doesn't matter. Also, as in Pablo's response, you will need to use UICollectionViewFlowLayout as the layout for your collection view. Finally, make sure you link the collectionView IBOutlet to your storyboard.

With the custom table view cell above, I can now subclass it in any other table view cell that needs a collection view and have it implement the UICollectionViewDelegateFlowLayout and UICollectionViewDataSource protocols. Hope this is helpful to someone else!

Answer 5

I read through all the answers. This seems to serve all cases.

override func systemLayoutSizeFitting(_ targetSize: CGSize, withHorizontalFittingPriority horizontalFittingPriority: UILayoutPriority, verticalFittingPriority: UILayoutPriority) -> CGSize {
        collectionView.layoutIfNeeded()
        collectionView.frame = CGRect(x: 0, y: 0, width: targetSize.width , height: 1)
        return collectionView.collectionViewLayout.collectionViewContentSize
}

Answer 6

An alternative to Pablo Romeu's solution is to customise UICollectionView itself, rather than doing the work in table view cell.

The underlying problem is that by default a collection view has no intrinsic size and so cannot inform auto layout of the dimensions to use. You can remedy that by creating a custom subclass which does return a useful intrinsic size.

Create a subclass of UICollectionView and override the following methods

override func intrinsicContentSize() -> CGSize {
    self.layoutIfNeeded()

    var size = super.contentSize
    if size.width == 0 || size.height == 0 {
        // return a default size
        size = CGSize(width: 600, height:44)
    }

    return size
 }

override func reloadData() {
    super.reloadData()
    self.layoutIfNeeded()
    self.invalidateIntrinsicContentSize()
}

(You should also override the related methods: reloadSections, reloadItemsAtIndexPaths in a similar way to reloadData())

Calling layoutIfNeeded forces the collection view to recalculate the content size which can then be used as the new intrinsic size.

Also, you need to explicitly handle changes to the view size (e.g. on device rotation) in the table view controller

    override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator)
{
    super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)
    dispatch_async(dispatch_get_main_queue()) {
        self.tableView.reloadData()
    }
}

Answer 7

Easiest approach I've came up with, so far, Credits to @igor answer above,

In your tableviewcell class just insert this

override func layoutSubviews() {
    self.collectionViewOutlet.constant = self.postPoll.collectionViewLayout.collectionViewContentSize.height
}

and of course, change the collectionviewoutlet with your outlet in the cell's class

Answer 8

I was facing the same issue recently and I almost tried every solution in the answers, some of them worked and others didn't my main concern about @PabloRomeu approach is that if you have other contents in the cell (other than the collection view) you will have to calculate their heights and the heights of their constraints and return the result to get the auto layout right and I don't like to calculate things manually in my code. So here is the solution that worked fine for me without doing any manual calculations in my code.

in the cellForRow:atIndexPath of the table view I do the following:

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    //do dequeue stuff
    //initialize the the collection view data source with the data
    cell.frame = CGRect.zero
    cell.layoutIfNeeded()
    return cell
}

I think what happens here is that I force the tableview cell to adjust its height after the collection view height has been calculated. (after providing the collectionView date to the data source)

Answer 9

I would put a static method on the collection view class that will return a size based on the content it will have. Then use that method in the heightForRowAtIndexPath to return the proper size.

Also note that you can get some weird behavior when you embed these kinds of viewControllers. I did it once and had some weird memory issues I never worked out.

Answer 10

Maybe my variant will be useful; i've been deciding this task during last two hours. I don't pretend it's 100% correct or optimal, but my skill's very small yet and i'd like to hear comments from experts. Thank you. One important note: this works for static table - it's specified by my current work. So, all I use is viewWillLayoutSubviews of tableView. And a little bit more.

private var iconsCellHeight: CGFloat = 500 

func updateTable(table: UITableView, withDuration duration: NSTimeInterval) {
    UIView.animateWithDuration(duration, animations: { () -> Void in
        table.beginUpdates()
        table.endUpdates()
    })
}

override func viewWillLayoutSubviews() {
    if let iconsCell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow: 0, inSection: 1)) as? CategoryCardIconsCell {
        let collectionViewContentHeight = iconsCell.iconsCollectionView.contentSize.height
        if collectionViewContentHeight + 17 != iconsCellHeight {
            iconsCellHeight = collectionViewContentHeight + 17
            updateTable(tableView, withDuration: 0.2)
        }
    }
}

override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
    switch (indexPath.section, indexPath.row) {
        case ...
        case (1,0):
            return iconsCellHeight
        default:
            return tableView.rowHeight
    }
}

1. I know, that the collectionView is located in the first row of the second section;
2. Let the height of the row is 17 p. bigger, than its content height;
3. iconsCellHeight is a random number as the program starts (i know, that in the portrait form it has to be exactly 392, but it's not important). If the content of collectionView + 17 is not equal this number, so change its value. Next time in this situation the condition gives FALSE;
4. After all update the tableView. In my case its the combination of two operations (for nice updating of extending rows);
5. And of course, in the heightForRowAtIndexPath add one row to code.

Answer 11

I get idea from @Igor post and invest my time to this for my project with swift

Just past this in your

 func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    //do dequeue stuff
    cell.frame = tableView.bounds
    cell.layoutIfNeeded()
    cell.collectionView.reloadData()
    cell.collectionView.heightAnchor.constraint(equalToConstant: cell.collectionView.collectionViewLayout.collectionViewContentSize.height)
    cell.layoutIfNeeded()
    return cell
}

Addition: If you see your UICollectionView choppy when loading cells.

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {       
  //do dequeue stuff
  cell.layer.shouldRasterize = true
  cell.layer.rasterizationScale = UIScreen.main.scale
  return cell
}

Answer 12

Pablo's solution did not work very well for me, I had strange visual effects (the collectionView not adjusting correctly).

What worked was to adjust the height constraint of the collectionView (as a NSLayoutConstraint) to the collectionView contentSize during layoutSubviews(). This is the method called when autolayout is applied to the cell.

// Constraint on the collectionView height in the storyboard. Priority set to 999.
@IBOutlet weak var collectionViewHeightConstraint: NSLayoutConstraint!


// Method called by autolayout to layout the subviews (including the collectionView).
// This is triggered with 'layoutIfNeeded()', or by the viewController
// (happens between 'viewWillLayoutSubviews()' and 'viewDidLayoutSubviews()'.
override func layoutSubviews() {

    collectionViewHeightConstraint.constant = collectionView.contentSize.height
    super.layoutSubviews()
}

// Call `layoutIfNeeded()` when you update your UI from the model to trigger 'layoutSubviews()'
private func updateUI() {
    layoutIfNeeded()
}

Answer 13

func configure(data: [Strings]) {
        
        names = data
        contentView.layoutIfNeeded()
        collectionviewNames.reloadData()
    }

Short and sweet. Consider the above method in your tableViewCell class. You would probably call it from func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell after dequeing your cell. Before calling reloadData on your collection view, in your tableCell, you need to tell the collection view to lay out its subviews, if layout updates are pending.

Answer 14

In your UITableViewDelegate:

-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return ceil(itemCount/4.0f)*collectionViewCellHeight;
}

Substitute itemCount and CollectionViewCellHeight with the real values. If you have an array of arrays itemCount might be:

self.items[indexPath.row].count

Or whatever.

Answer 15

1.Create dummy cell.
2.Use collectionViewContentSize method on UICollectionViewLayout of UICollectionView using current data.

Answer 16

You can calculate the height of the collection based on its properties like itemSize, sectionInset, minimumLineSpacing, minimumInteritemSpacing, if your collectionViewCell has the border of a rule.