How to display specific cell of UICollectionView using viewForSupplementaryElementOfKind - swift - ios

Question

I am a new iOS programming. and now i am developing an app which display similar to appstore. But i have some problems which when user open the app so, i want cell of data should be display the second cell. for example, i have three cell then when user open the app the second cell should be automatically scrolled to that position.
Here is how i created header section: (programmatically)
/// banner section
override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
let header = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: headerCellId, for: indexPath) as! HeaderBanner
header.sectionCategory = dashbordCell?[indexPath.item]
return header
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
let size = CGSize(width: view.frame.width, height: 370)
return size
}
Here is I created HeaderBanner
let dataBannerCollectionView: UICollectionView = {
var scrollInterval: Int = 3
let flowLayout = UICollectionViewFlowLayout()
flowLayout.scrollDirection = .horizontal
let collectionView = UICollectionView(frame: .zero,collectionViewLayout: flowLayout)
collectionView.backgroundColor = UIColor.clear
collectionView.translatesAutoresizingMaskIntoConstraints = false
return collectionView
}()
func setupViewsCell(){
dataBannerCollectionView.showsHorizontalScrollIndicator = false
dataBannerCollectionView.dataSource = self
dataBannerCollectionView.delegate = self
dataBannerCollectionView.register(HeaderBannerDataCell.self, forCellWithReuseIdentifier: headerCellId)
addSubview(dataBannerCollectionView)
setupConstraintDataBannerCollectionView()
}
Here is behavior of HeaderBanner file.
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if let count = sectionCategory?.dataBanner?.count {
return count
}
return 0
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: headerCellId, for: indexPath) as! HeaderBannerDataCell
cell.dataBannerCell = sectionCategory?.dataBanner![indexPath.item]
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
print(frame.width)
let size = CGSize(width: frame.width - 100 , height: 350)
return size
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
print("Banner selected")
}
As you can see the header section display the first cell of image. I just my app look like this when user opens the app .
Here is output of my sample app:
Here is my expectation which i want to display the middle cell of all cells.

Answer 1

You can use the scrollToItem function of UICollectionView:
if you have three cells for example:
dataBannerCollectionView.scrollToItem(at: IndexPath(item: 2, section: 0), at: UICollectionViewScrollPosition.centeredHorizontally, animated: false)
Add that code in setupViewsCell() function