Why are 2 network calls using the same search string required before the UICollectionView decides there is data that needs to be refreshed? - ios

Question

I have a strange problem in a UIViewController that the user uses to search for a GIF.
There are essentially 2 issues:
The user has to enter the same search term twice before the UICollectionView triggers the cellForRowAt data source method after a call is made to reloadData().
After you enter the search term the first time, heightChanged() is called, but the self.GIFCollectionView.collectionViewLayout.collectionViewContentSize.height comes back as 0 even though I've confirmed that data is being received back from the server. The second time you enter the search term, the height is a non-zero value and the collection view shows the cells.
Here is an example of how I have to get the data to show up:
Launch app, go this UIViewController
Enter a search term (ie. "baseball")
Nothing shows up (even though reloadData() was called and new data is in the view model.)
Delete a character from the search term (ie. "basebal")
Type in the missing character (ie. "baseball")
The UICollectionView refreshes via a call to reloadData() and then calls cellForRowAt:.
Here is the entire View Controller:
import UIKit
protocol POGIFSelectViewControllerDelegate: AnyObject {
func collectionViewHeightDidChange(_ height: CGFloat)
func didSelectGIF(_ selectedGIFURL: POGIFURLs)
}
class POGIFSelectViewController: UIViewController {
//MARK: - Constants
private enum Constants {
static let POGIFCollectionViewCellIdentifier: String = "POGIFCollectionViewCell"
static let verticalPadding: CGFloat = 16
static let searchBarHeight: CGFloat = 40
static let searchLabelHeight: CGFloat = 24
static let activityIndicatorTopSpacing: CGFloat = 10
static let gifLoadDuration: Double = 0.2
static let gifStandardFPS: Double = 1/30
static let gifMaxDuration: Double = 5.0
}
//MARK: - Localized Strings
let localizedSearchGIFs = PALocalizedStringFromTable("RECOGNITION_IMAGE_SELECTION_GIF_BODY_TITLE", table: "Recognition-Osiris", comment: "Search GIFs") as String
//MARK: - Properties
var viewModel: POGIFSearchViewModel?
var activityIndicator = MDCActivityIndicator()
var gifLayout = PAGiphyCellLayout()
var selectedGIF: POGIFURLs?
//MARK: - IBOutlet
#IBOutlet weak var GIFCollectionView: UICollectionView!
#IBOutlet weak var searchGIFLabel: UILabel! {
didSet {
self.searchGIFLabel.text = self.localizedSearchGIFs
}
}
#IBOutlet weak var searchField: POSearchField! {
didSet {
self.searchField.delegate = self
}
}
#IBOutlet weak var activityIndicatorContainer: UIView!
//MARK: - Delegate
weak var delegate: POGIFSelectViewControllerDelegate?
//MARK: - View Lifecycle Methods
override func viewDidLoad() {
super.viewDidLoad()
self.setupActivityIndicator(activityIndicator: self.activityIndicator, activityIndicatorContainer: self.activityIndicatorContainer)
self.viewModel = POGIFSearchViewModel(data: PAData.sharedInstance())
if let viewModel = self.viewModel {
viewModel.viewDelegate = self
viewModel.viewDidBeginLoading()
}
self.gifLayout.delegate = self
self.gifLayout.isAXPGifLayout = true;
self.GIFCollectionView.collectionViewLayout = self.gifLayout
self.GIFCollectionView.backgroundColor = .orange
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
// This Patch is to fix a bug where GIF contentSize was not calculated correctly on first load.
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + .seconds(1)) {
self.viewModel?.viewDidBeginLoading()
}
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
self.heightChanged()
}
//MARK: - Helper Methods
func heightChanged() {
guard let delegate = self.delegate else { return }
let height = self.GIFCollectionView.collectionViewLayout.collectionViewContentSize.height + Constants.verticalPadding * 3 + Constants.searchLabelHeight + Constants.searchBarHeight + activityIndicatorContainer.frame.size.height + Constants.activityIndicatorTopSpacing
print("**** Items in Collection View -> self.viewModel?.gifModel.items.count: \(self.viewModel?.gifModel.items.count)")
print("**** self.GIFCollectionView.collectionViewLayout.collectionViewContentSize.height: \(self.GIFCollectionView.collectionViewLayout.collectionViewContentSize.height); height: \(height)")
delegate.collectionViewHeightDidChange(height)
}
func reloadCollectionView() {
self.GIFCollectionView.collectionViewLayout.invalidateLayout()
self.GIFCollectionView.reloadData()
self.GIFCollectionView.layoutIfNeeded()
self.heightChanged()
}
func imageAtIndexPath(_ indexPath: IndexPath) -> UIImage? {
guard let previewURL = self.viewModel?.gifModel.items[indexPath.row].previewGIFURL else { return nil }
var loadedImage: UIImage? = nil
let imageManager = SDWebImageManager.shared()
imageManager.loadImage(with: previewURL, options: .lowPriority, progress: nil) { (image: UIImage?, data: Data?, error: Error?, cacheType: SDImageCacheType, finished: Bool, imageURL: URL?) in
loadedImage = image
}
return loadedImage
}
func scrollViewDidScrollToBottom() {
guard let viewModel = self.viewModel else { return }
if viewModel.viewDidSearchMoreGIFs() {
self.activityIndicator.startAnimating()
} else {
self.activityIndicator.stopAnimating()
}
}
}
extension POGIFSelectViewController: POSearchFieldDelegate {
func searchFieldTextChanged(text: String?) {
guard let viewModel = self.viewModel else { return }
viewModel.viewDidSearchGIFs(withSearchTerm: text)
}
}
extension POGIFSelectViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
print("**** CELL FOR ROW AT -> self.viewModel?.gifModel.items.count: \(self.viewModel?.gifModel.items.count)")
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: Constants.POGIFCollectionViewCellIdentifier, for: indexPath) as! POGIFCollectionViewCell
guard let previewURL = self.viewModel?.gifModel.items[indexPath.row].previewGIFURL else {
return cell
}
var cellState: POGIFCollectionViewCell.CellState = .dimmedState
if self.selectedGIF == nil {
cellState = .defaultState
} else if (self.selectedGIF?.previewGIFURL?.absoluteString == previewURL.absoluteString) {
cellState = .selectedState
}
cell.setupUI(withState: cellState, URL: previewURL) { [weak self] () in
UIView.animate(withDuration: Constants.gifLoadDuration) {
guard let weakSelf = self else { return }
weakSelf.GIFCollectionView.collectionViewLayout.invalidateLayout()
}
}
if cell.GIFPreviewImageView.animationDuration > Constants.gifMaxDuration {
cell.GIFPreviewImageView.animationDuration = Constants.gifMaxDuration
}
cell.backgroundColor = .green
return cell
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
guard let viewModel = self.viewModel else { return 0 }
return viewModel.gifModel.items.count
}
}
extension POGIFSelectViewController: UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
guard let selectedGIF = self.viewModel?.gifModel.items[indexPath.row],
let delegate = self.delegate else {
return
}
self.selectedGIF = selectedGIF
delegate.didSelectGIF(selectedGIF)
self.reloadCollectionView()
}
}
extension POGIFSelectViewController: POGIFSearchViewModelToViewProtocol {
func didFetchGIFsWithSuccess() {
self.activityIndicator.stopAnimating()
print("**** didFetchGIFsWithSuccess() -> about to reload collection view")
self.reloadCollectionView()
}
func didFetchGIFsWithError(_ error: Error!, request: PARequest!) {
self.activityIndicator.stopAnimating()
}
}
extension POGIFSelectViewController: PAGiphyLayoutCellDelegate {
func heightForCell(givenWidth cellWidth: CGFloat, at indexPath: IndexPath!) -> CGFloat {
guard let image = self.imageAtIndexPath(indexPath) else {
return 0
}
if (image.size.height < 1 || image.size.width < 1 || self.activityIndicator.isAnimating) {
return cellWidth
}
let scaleFactor = image.size.height / image.size.width
let imageViewToHighlightedViewSpacing: CGFloat = 4 // this number comes from 2 * highlightedViewBorderWidth from POGIFCollectionViewCell
return cellWidth * scaleFactor + imageViewToHighlightedViewSpacing
}
func heightForHeaderView() -> CGFloat {
return 0
}
}
You'll see that the heightChanged() method calls a delegate method. That method is in another UIViewController:
func collectionViewHeightDidChange(_ height: CGFloat) {
self.collectionViewHeightConstraint.constant = height
}
So, I can't figure out why I need to either delete a character from the search term and re-add it in order for the data to refresh even though the very first call populated the view model with new data.
It's bizarre. Please help.