Handle scrollview size in UICollectionViewCell

Question

Im making an horizontal UICollectionView, and inside UICollectionViewCell i have scrollview and inside the scrollview i have an imageView.

The issue I'm having is that when i zoom-in the imageView,scrollView is taking all the cell size, so its not fitting to the image size height and width.thus by scrolling up and down the image disappear from scrollview, i have no idea whats going wrong in my code.

My ColectionViewCell code:

class CollectionViewCell: UICollectionViewCell {
    @IBOutlet var scrollView: UIScrollView!
    @IBOutlet var ImageV: UIImageView!
}

CollectionView code :

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
  let cell = collectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) as! CollectionViewCell

  cell.scrollView.contentMode = UIViewContentMode.ScaleAspectFit
  cell.scrollView.delegate = self
  cell.ImageV.image = UIImage(named: array[indexPath.row])
  cell.ImageV.contentMode = UIViewContentMode.ScaleAspectFit

  cell.scrollView.minimumZoomScale = 1
  cell.scrollView.maximumZoomScale = 4;
  cell.scrollView.contentSize = cell.ImageV.frame.size

  return cell
}

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {

  return CGSize(width: self.collectionView.frame.size.width , height: self.collectionView.frame.size.height - 100)

}

func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {

  let indexPath = NSIndexPath(forItem: Int(currentIndex), inSection: 0)

  if let cell1 = self.collectionView.cellForItemAtIndexPath(indexPath) {  
    let cell = cell1 as! CollectionViewCell
    let boundsSize = cell.scrollView.bounds.size
    var contentsFrame = cell.ImageV.frame

    if contentsFrame.size.width < boundsSize.width{
      contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2
    }else{
      contentsFrame.origin.x = 0
    }

    if contentsFrame.size.height < boundsSize.height {
      contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2
    }else{
      contentsFrame.origin.y = 0
    }
    return cell.ImageV    
  }      
   return UIView()     
 }


func scrollViewDidEndDecelerating(scrollView: UIScrollView) {

  currentIndex = self.collectionView.contentOffset.x / self.collectionView.frame.size.width;
  oldcell = currentIndex - 1

  let indexPath = NSIndexPath(forItem: Int(oldcell), inSection: 0)
  if let cell1 = self.collectionView.cellForItemAtIndexPath(indexPath) {
    let cell = cell1 as! CollectionViewCell
    cell.scrollView.zoomScale = 0 
  }
}

Image preview: https://i.imgur.com/Gr2p09A.gifv

My project found here : https://drive.google.com/file/d/0B32ROW7V8Fj4RVZfVGliXzJseGM/view?usp=sharing

Answer 1

Well First lets start with UIViewController that is holding your UICollectionView:

Define a variable to hold the collection view layout:

var flowLayout:UICollectionViewFlowLayout = UICollectionViewFlowLayout()

You will have to override viewWillLayoutSubviews and this is going to handle the collectionView size.

override func viewWillLayoutSubviews() {
    super.viewWillLayoutSubviews()

    flowLayout.itemSize = CGSize(width: view.frame.width, height:view.frame.height)

}

Also you will need to override viewDidLayoutSubviews to handle the size of each new cell to set it to default size:

    override func viewDidLayoutSubviews() {

        if let currentCell = imageCollectionView.cellForItemAtIndexPath(desiredIndexPath) as? GalleryCell {
            currentCell.configureForNewImage()
        }
}

in ViewDidLoad setup the collectionView to be horizontal with flow layout:

    // Set up flow layout
    flowLayout.scrollDirection = UICollectionViewScrollDirection.Horizontal
    flowLayout.minimumInteritemSpacing = 0
    flowLayout.minimumLineSpacing = 0

    // Set up collection view
    imageCollectionView = UICollectionView(frame: CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height), collectionViewLayout: flowLayout)

    imageCollectionView.translatesAutoresizingMaskIntoConstraints = false
    imageCollectionView.registerClass(GalleryCell.self, forCellWithReuseIdentifier: "GalleryCell")
    imageCollectionView.dataSource = self
    imageCollectionView.delegate = self
    imageCollectionView.pagingEnabled = true
    view.addSubview(imageCollectionView)

    imageCollectionView.contentSize = CGSize(width: 1000.0, height: 1.0)

In your UICollectionView method cellForItemAtIndexPath load the image only without setting anything:

 cell.image = UIImage(named: array[indexPath.row])

Now lets move to GalleryCell class and to handle scrollView when zooming:

class GalleryCell: UICollectionViewCell, UIScrollViewDelegate {

    var image:UIImage? {
        didSet {
            configureForNewImage()
        }
    }

     var scrollView: UIScrollView
     let imageView: UIImageView

   override init(frame: CGRect) {

        imageView = UIImageView()
        imageView.translatesAutoresizingMaskIntoConstraints = false
        scrollView = UIScrollView(frame: frame)
        scrollView.translatesAutoresizingMaskIntoConstraints = false

        super.init(frame: frame)
        contentView.addSubview(scrollView)
        contentView.addConstraints(scrollViewConstraints)

        scrollView.addSubview(imageView)

        scrollView.delegate = self
        scrollView.maximumZoomScale = 4
    }

    required public init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    internal func configureForNewImage() {
        imageView.image = image
        imageView.sizeToFit()

        setZoomScale()
        scrollViewDidZoom(scrollView)
    }

    public func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
        return imageView
    }

    public func scrollViewDidZoom(scrollView: UIScrollView) {

        let imageViewSize = imageView.frame.size
        let scrollViewSize = scrollView.bounds.size

        let verticalPadding = imageViewSize.height < scrollViewSize.height ? (scrollViewSize.height - imageViewSize.height) / 2 : 0
        let horizontalPadding = imageViewSize.width < scrollViewSize.width ? (scrollViewSize.width - imageViewSize.width) / 2 : 0

        if verticalPadding >= 0 {
            // Center the image on screen
            scrollView.contentInset = UIEdgeInsets(top: verticalPadding, left: horizontalPadding, bottom: verticalPadding, right: horizontalPadding)
        } else {
            // Limit the image panning to the screen bounds
            scrollView.contentSize = imageViewSize
        }


}

I've tested it with example and it should solve your issue with scrollview and @Spencevail explained mostly why it's being caused !