Interaction between UIPageViewController and it's Thumbnails CollectionView - swift

Question

In my app using UIPageViewController to display full size images, and at the bottom of screen have thumbnail CollectionView each thumbnail is representing UIPageViewController full size image.My question is how to achieve paging of UIpageViewController when user select different thumbnail collection view cell?
if anyone know how to achieve this functionality , please help me with code or advice or links. Thanks
I believe I have to work with UICollectionView’s didSelectItemAtIndexPath method ,but not too sure how best to do it and would really appreciate help, please.
My Collection View File
protocol ThumbnailViewDelegate: class {
func didSelectThumbnail(at index: Int)
}
class ThumbnailView: UIView, UICollectionViewDelegate, UICollectionViewDataSource,UICollectionViewDelegateFlowLayout, PhotoCollectionViewModelPresenter{
weak var delegate: ThumbnailViewDelegate?
var assets: [PHAsset] = []
private let viewModel = PhotoCollectionViewModel()
//private var myViewModel: DetailViewModel!
private let imageDownloader = ImageDownloader(targetSize: CGSize(width: 80, height: 80 ))
//var selectedImage: UIImage?
lazy var thumbnailCollectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .horizontal
let view = UICollectionView(frame: CGRect.zero, collectionViewLayout: layout)
view.translatesAutoresizingMaskIntoConstraints = false
view.isPagingEnabled = true
view.delegate = self
view.dataSource = self
view.isPrefetchingEnabled = false
view.register(ThumbnailCollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
let cellImageView = ThumbnailCollectionViewCell()
view.addSubview(cellImageView.imageView)
view.backgroundColor = UIColor.white
return view
}()
let imageView: ThumbnailCollectionViewCell = {
let view = ThumbnailCollectionViewCell()
view.contentMode = .scaleAspectFit
view.translatesAutoresizingMaskIntoConstraints = false
return view
}()
override init(frame: CGRect) {
super.init(frame: frame)
self.addSubview(thumbnailCollectionView)
thumbnailCollectionView.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
thumbnailCollectionView.rightAnchor.constraint(equalTo: rightAnchor).isActive = true
thumbnailCollectionView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
thumbnailCollectionView.heightAnchor.constraint(equalToConstant: 100).isActive = true
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
func propagateReload() {
thumbnailCollectionView.reloadData()
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return assets.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath as IndexPath) as! ThumbnailCollectionViewCell
cell.layer.masksToBounds = true
cell.layer.cornerRadius = 8
let image = assets[indexPath.item]
imageDownloader.download(asset: image) { [weak self] (image) in
self?.configureCell(indexPath: indexPath, image: image)
}
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
{
return CGSize(width: 80.0, height: 80.0)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
delegate?.didSelectThumbnail(at: indexPath.item)
}
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
}
func configureCell(indexPath: IndexPath, image: UIImage) {
guard let cell = thumbnailCollectionView.cellForItem(at: indexPath) as? ThumbnailCollectionViewCell else {
return
}
cell.configure(image: image)
}
}
PageViewController File
class MainPageViewController: UIPageViewController {
var mainImageIndex: Int?
var pageViewModels: [DetailPageViewModel]!
var viewModel: DetailViewModel!
var collectionAssets: [PHAsset] = []
var selectedAsset: UIImage?
private var pendingIndex: Int?
// Collection View
lazy var collectionView: ThumbnailView = {
let view = ThumbnailView()
view.delegate = self
view.assets = self.collectionAssets
view.translatesAutoresizingMaskIntoConstraints = false
return view
}()
//MARK: - Create VC
lazy var pageViewControllersArray: [PageViewController] = {
return pageViewModels.map {
return PageViewController(viewModel: $0)
}
}()
var currentIndex:Int {
get {
return pageViewControllersArray.index(of: self.viewControllers!.first! as! PageViewController)!
}
set {
guard newValue >= 0,
newValue < pageViewControllersArray.count else {
return
}
let vc = pageViewControllersArray[newValue]
let direction:UIPageViewController.NavigationDirection = newValue > currentIndex ? .forward : .reverse
self.setViewControllers([vc], direction: direction, animated: true, completion: nil)
}
}
override func viewDidLoad() {
super.viewDidLoad()
dataSource = self
delegate = self
view.backgroundColor = UIColor.white
setViewControllers([pageViewControllersArray[mainImageIndex ?? 0]], direction: .forward, animated: true, completion: nil)
self.view.addSubview(collectionView)
setupCollectioViewAutoLayout()
}
func setupCollectioViewAutoLayout(){
collectionView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
collectionView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
collectionView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
collectionView.heightAnchor.constraint(equalToConstant: 100).isActive = true
}
func viewWillAppear() {
super.viewWillAppear(true)
}
}
extension MainPageViewController: UIPageViewControllerDelegate, UIPageViewControllerDataSource, ThumbnailViewDelegate {
func didSelectThumbnail(at index: Int) {
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
guard let viewController = viewController as? PageViewController else {return nil}
if let index = pageViewControllersArray.index(of: viewController){
if index > 0{
return pageViewControllersArray[index - 1]
}
}
return nil
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
guard let viewController = viewController as? PageViewController else {return nil}
if let index = pageViewControllersArray.index(of: viewController){
if index < pageViewControllersArray.count - 1{
return pageViewControllersArray[index + 1]
}
}
return nil
}
func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
return pageViewControllersArray.count
}
func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
return currentIndex
}
}

Answer 1

When the select method is called, show another page view or page view controller on the whole screen.