241 lines
11 KiB
Swift
241 lines
11 KiB
Swift
//
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// ThreeLayerCollectionViewController.swift
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// MVMCoreUI
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//
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// Created by Scott Pfeil on 4/6/20.
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// Copyright © 2020 Verizon Wireless. All rights reserved.
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//
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import Foundation
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/// A view controller that has three main layers, a header, collection rows, and a footer. The header is added as a supplement header to the first section, and the footer is added as a supplement footer to the last section. This view controller allows for flexible space between the three layers to fit the screeen.
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@objc open class ThreeLayerCollectionViewController: ProgrammaticCollectionViewController, UICollectionViewDelegateFlowLayout {
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private var topView: UIView?
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private var bottomView: UIView?
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private var headerView: ContainerCollectionReusableView?
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private var footerView: ContainerCollectionReusableView?
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private let headerID = "header"
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private let footerID = "footer"
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public var bottomViewOutsideOfScrollArea: Bool = false
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public var topViewOutsideOfScrollArea: Bool = false
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open override func updateViewConstraints() {
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// Update the spacing on constraint update
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updateFlexibleSpace()
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super.updateViewConstraints()
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}
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/// Updates the padding for flexible space (header or footer)
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private func updateFlexibleSpace() {
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guard let collectionView = collectionView else { return }
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let minimumSpace: CGFloat = minimumFillSpace()
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var currentSpace: CGFloat = 0
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var totalMinimumSpace: CGFloat = 0
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var fillTop = false
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if spaceBelowTopView() == nil, headerView != nil {
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fillTop = true
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currentSpace += headerView?.bottomConstraint?.constant ?? 0
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totalMinimumSpace += minimumSpace
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}
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var fillBottom = false
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if spaceAboveBottomView() == nil, footerView != nil {
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fillBottom = true
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currentSpace += footerView?.topConstraint?.constant ?? 0
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totalMinimumSpace += minimumSpace
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}
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guard fillTop || fillBottom else { return }
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let newSpace = MVMCoreUIUtility.getVariableConstraintHeight(currentSpace, in: collectionView, minimumHeight: totalMinimumSpace)
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if !MVMCoreGetterUtility.cgfequalwiththreshold(newSpace, currentSpace, 1) {
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if fillTop && fillBottom {
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// space both
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let half = newSpace / 2
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headerView?.bottomConstraint?.constant = half
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footerView?.topConstraint?.constant = half
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collectionView.collectionViewLayout.invalidateLayout()
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} else if fillTop {
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// Only top is spaced.
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headerView?.bottomConstraint?.constant = newSpace
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collectionView.collectionViewLayout.invalidateLayout()
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} else if fillBottom {
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// Only bottom is spaced.
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footerView?.topConstraint?.constant = newSpace
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collectionView.collectionViewLayout.invalidateLayout()
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}
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}
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}
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func addTopViewOutside() {
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guard let collectionView = collectionView, let topView = topView else { return }
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view.addSubview(topView)
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topView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true
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topView.leftAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leftAnchor).isActive = true
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view.safeAreaLayoutGuide.rightAnchor.constraint(equalTo: topView.rightAnchor).isActive = true
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collectionView.topAnchor.constraint(equalTo: topView.bottomAnchor).isActive = true
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}
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func addBottomViewOutside() {
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guard let collectionView = collectionView, let bottomView = bottomView else { return }
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view.addSubview(bottomView)
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bottomView.topAnchor.constraint(equalTo: collectionView.bottomAnchor).isActive = true
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bottomView.leftAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leftAnchor).isActive = true
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view.safeAreaLayoutGuide.rightAnchor.constraint(equalTo: bottomView.rightAnchor).isActive = true
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view.safeAreaLayoutGuide.bottomAnchor.constraint(equalTo: bottomView.bottomAnchor).isActive = true
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}
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//MARK: - ViewController
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open override func updateViews() {
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super.updateViews()
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// Needed due to dispatch in reloadCollectionData.
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DispatchQueue.main.async {
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let width = self.view.bounds.width
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if let topView = self.topView as? MVMCoreViewProtocol {
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topView.updateView(width)
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}
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if let bottomView = self.bottomView as? MVMCoreViewProtocol {
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bottomView.updateView(width)
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}
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if let cells = self.collectionView?.visibleCells {
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for cell in cells {
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self.update(cell: cell, size: width)
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}
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}
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self.invalidateCollectionLayout()
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}
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}
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open override func updateUI(for molecules: [MoleculeModelProtocol]? = nil) {
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super.updateUI(for: molecules)
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topView?.removeFromSuperview()
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bottomView?.removeFromSuperview()
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topView = viewForTop()
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bottomView = viewForBottom()
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if topViewOutsideOfScrollArea {
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topConstraint?.isActive = false
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addTopViewOutside()
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} else {
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topConstraint?.isActive = true
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}
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if bottomViewOutsideOfScrollArea {
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bottomConstraint?.isActive = false
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addBottomViewOutside()
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} else {
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bottomConstraint?.isActive = true
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}
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reloadCollectionData()
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}
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override open func viewDidLoad() {
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super.viewDidLoad()
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// Do any additional setup after loading the view.
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collectionView?.frameChangeAction = { [weak self] in
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self?.invalidateCollectionLayout()
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}
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}
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//MARK: - Spacing
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// If both are subclassed to return a value, then the buttons will not be pinned towards the bottom because neither spacing would try to fill the screen.
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/// Space between the top view and the collection rows, nil to fill. 0 default
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open func spaceBelowTopView() -> CGFloat? {
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return 0
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}
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/// Space between the bottom view and the collection rows, nil to fill. nil default
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open func spaceAboveBottomView() -> CGFloat? {
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return nil
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}
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/// can override to return a minimum fill space. 0 default
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open func minimumFillSpace() -> CGFloat {
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return 0
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}
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//MARK: - Functions to subclass
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/// Subclass for a top view.
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open func viewForTop() -> UIView? {
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return nil
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}
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/// Subclass for a bottom view.
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open func viewForBottom() -> UIView? {
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return nil
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}
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//MARK: - Collection
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/// Should be used to refresh the layout of the collection view. Updates flexible padding.
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open func invalidateCollectionLayout() {
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self.collectionView?.collectionViewLayout.invalidateLayout()
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// TODO: Improve this workaround (autolayout for cells happens async so contentSize isn't accurate immediately)
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DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.1, execute: {
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self.updateFlexibleSpace()
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})
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}
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/// Should be used to reload the data of the collection view. Updates flexible padding.
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open func reloadCollectionData() {
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collectionView?.reloadData()
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// TODO: Improve this workaround (autolayout for cells happens async so contentSize isn't accurate immediately)
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DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.1, execute: {
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self.updateFlexibleSpace()
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})
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}
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/// Called in updateView, updates the cell.
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open func update(cell: UICollectionViewCell, size: CGFloat) {
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(cell as? MVMCoreViewProtocol)?.updateView(size)
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}
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open override func registerCells() {
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super.registerCells()
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collectionView?.register(ContainerCollectionReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: headerID)
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collectionView?.register(ContainerCollectionReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionFooter, withReuseIdentifier: footerID)
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}
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open override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
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return 0
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}
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open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
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guard section == 0 else { return .zero }
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// Calculate the height of the header since apple doesn't support autolayout. Width is fixed, height is tall as content.
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let header = headerView ?? self.collectionView(collectionView, viewForSupplementaryElementOfKind: UICollectionView.elementKindSectionHeader, at: IndexPath(row: 0, section: section))
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return header.systemLayoutSizeFitting(CGSize(width: collectionView.frame.width, height: UIView.layoutFittingExpandedSize.height), withHorizontalFittingPriority: .required, verticalFittingPriority: .fittingSizeLevel)
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}
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open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
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guard section == numberOfSections(in: collectionView) - 1 else { return .zero }
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// Calculate the height of the footr since apple doesn't support autolayout. Width is fixed, height is tall as content.
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let footer = footerView ?? self.collectionView(collectionView, viewForSupplementaryElementOfKind: UICollectionView.elementKindSectionFooter, at: IndexPath(row: 0, section: section))
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return footer.systemLayoutSizeFitting(CGSize(width: collectionView.frame.width, height: UIView.layoutFittingExpandedSize.height), withHorizontalFittingPriority: .required, verticalFittingPriority: .fittingSizeLevel)
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}
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open func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
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if kind == UICollectionView.elementKindSectionFooter,
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let footerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: footerID, for: indexPath) as? ContainerCollectionReusableView {
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let bottomView = (bottomViewOutsideOfScrollArea ? nil : self.bottomView) ?? MVMCoreUICommonViewsUtility.getView(with: 0.5)
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footerView.addAndContain(view: bottomView)
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footerView.topConstraint?.constant = spaceAboveBottomView() ?? 0
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self.footerView = footerView
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return footerView
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} else if kind == UICollectionView.elementKindSectionHeader,
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let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: headerID, for: indexPath) as? ContainerCollectionReusableView {
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let topView = (topViewOutsideOfScrollArea ? nil : self.topView) ?? MVMCoreUICommonViewsUtility.getView(with: 0.5)
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headerView.addAndContain(view: topView)
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headerView.bottomConstraint?.constant = spaceBelowTopView() ?? 0
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self.headerView = headerView
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return headerView
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}
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fatalError()
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}
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open func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
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(collectionView.cellForItem(at: indexPath) as? CollectionTemplateItemProtocol)?.didSelectCell(at: indexPath, delegateObject: delegateObjectIVar, additionalData: nil)
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}
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}
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