Details
- Xcode 10.2 (10E125), Swift 5
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Coding for iOS 11: How to drag & drop into collections & tables
Full Sample
ViewController
import UIKit
enum CellModel {
case simple(text: String)
case availableToDrop
}
class ViewController: UIViewController {
private lazy var cellIdentifier = "cellIdentifier"
private lazy var supplementaryViewIdentifier = "supplementaryViewIdentifier"
private lazy var sections = 10
private lazy var itemsInSection = 2
private lazy var numberOfElementsInRow = 3
private lazy var data: [[CellModel]] = {
var count = 0
return (0 ..< sections).map { _ in
return (0 ..< itemsInSection).map { _ -> CellModel in
count += 1
return .simple(text: "cell (count)")
}
}
}()
override func viewDidLoad() {
super.viewDidLoad()
let collectionViewFlowLayout = UICollectionViewFlowLayout()
collectionViewFlowLayout.minimumLineSpacing = 5
collectionViewFlowLayout.minimumInteritemSpacing = 5
let _numberOfElementsInRow = CGFloat(numberOfElementsInRow)
let allWidthBetwenCells = _numberOfElementsInRow == 0 ? 0 : collectionViewFlowLayout.minimumInteritemSpacing*(_numberOfElementsInRow-1)
let width = (view.frame.width - allWidthBetwenCells)/_numberOfElementsInRow
collectionViewFlowLayout.itemSize = CGSize(width: width, height: width)
collectionViewFlowLayout.headerReferenceSize = CGSize(width: 0, height: 40)
let collectionView = UICollectionView(frame: .zero, collectionViewLayout: collectionViewFlowLayout)
collectionView.backgroundColor = .white
view.addSubview(collectionView)
collectionView.translatesAutoresizingMaskIntoConstraints = false
collectionView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true
collectionView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
collectionView.leftAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leftAnchor).isActive = true
collectionView.rightAnchor.constraint(equalTo: view.safeAreaLayoutGuide.rightAnchor).isActive = true
collectionView.register(CollectionViewCell.self, forCellWithReuseIdentifier: cellIdentifier)
collectionView.register(SupplementaryView.self,
forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader,
withReuseIdentifier: supplementaryViewIdentifier)
collectionView.dragInteractionEnabled = true
collectionView.reorderingCadence = .fast
collectionView.dropDelegate = self
collectionView.dragDelegate = self
collectionView.delegate = self
collectionView.dataSource = self
}
}
extension ViewController: UICollectionViewDelegate { }
extension ViewController: UICollectionViewDataSource {
func numberOfSections(in collectionView: UICollectionView) -> Int { return data.count }
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return data[section].count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
switch data[indexPath.section][indexPath.item] {
case .simple(let text):
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! CollectionViewCell
cell.label?.text = text
cell.backgroundColor = .gray
return cell
case .availableToDrop:
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! CollectionViewCell
cell.backgroundColor = UIColor.green.withAlphaComponent(0.3)
return cell
}
}
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: supplementaryViewIdentifier, for: indexPath as IndexPath) as! SupplementaryView
return headerView
}
}
extension ViewController: UICollectionViewDragDelegate {
func collectionView(_ collectionView: UICollectionView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem] {
let itemProvider = NSItemProvider(object: "(indexPath)" as NSString)
let dragItem = UIDragItem(itemProvider: itemProvider)
dragItem.localObject = data[indexPath.section][indexPath.row]
return [dragItem]
}
func collectionView(_ collectionView: UICollectionView, itemsForAddingTo session: UIDragSession, at indexPath: IndexPath, point: CGPoint) -> [UIDragItem] {
let itemProvider = NSItemProvider(object: "(indexPath)" as NSString)
let dragItem = UIDragItem(itemProvider: itemProvider)
dragItem.localObject = data[indexPath.section][indexPath.row]
return [dragItem]
}
func collectionView(_ collectionView: UICollectionView, dragSessionWillBegin session: UIDragSession) {
var itemsToInsert = [IndexPath]()
(0 ..< data.count).forEach {
itemsToInsert.append(IndexPath(item: data[$0].count, section: $0))
data[$0].append(.availableToDrop)
}
collectionView.insertItems(at: itemsToInsert)
}
func collectionView(_ collectionView: UICollectionView, dragSessionDidEnd session: UIDragSession) {
var removeItems = [IndexPath]()
for section in 0..<data.count {
for item in 0..<data[section].count {
switch data[section][item] {
case .availableToDrop: removeItems.append(IndexPath(item: item, section: section))
case .simple: break
}
}
}
removeItems.forEach { data[$0.section].remove(at: $0.item) }
collectionView.deleteItems(at: removeItems)
}
}
extension ViewController: UICollectionViewDropDelegate {
func collectionView(_ collectionView: UICollectionView, performDropWith coordinator: UICollectionViewDropCoordinator) {
let destinationIndexPath: IndexPath
if let indexPath = coordinator.destinationIndexPath {
destinationIndexPath = indexPath
} else {
let section = collectionView.numberOfSections - 1
let row = collectionView.numberOfItems(inSection: section)
destinationIndexPath = IndexPath(row: row, section: section)
}
switch coordinator.proposal.operation {
case .move:
reorderItems(coordinator: coordinator, destinationIndexPath:destinationIndexPath, collectionView: collectionView)
case .copy:
copyItems(coordinator: coordinator, destinationIndexPath: destinationIndexPath, collectionView: collectionView)
default: return
}
}
func collectionView(_ collectionView: UICollectionView, canHandle session: UIDropSession) -> Bool { return true }
func collectionView(_ collectionView: UICollectionView, dropSessionDidUpdate session: UIDropSession, withDestinationIndexPath destinationIndexPath: IndexPath?) -> UICollectionViewDropProposal {
if collectionView.hasActiveDrag, let destinationIndexPath = destinationIndexPath {
switch data[destinationIndexPath.section][destinationIndexPath.row] {
case .simple:
return UICollectionViewDropProposal(operation: .move, intent: .insertAtDestinationIndexPath)
case .availableToDrop:
return UICollectionViewDropProposal(operation: .move, intent: .insertIntoDestinationIndexPath)
}
} else { return UICollectionViewDropProposal(operation: .forbidden) }
}
private func reorderItems(coordinator: UICollectionViewDropCoordinator, destinationIndexPath: IndexPath, collectionView: UICollectionView) {
let items = coordinator.items
if items.count == 1, let item = items.first,
let sourceIndexPath = item.sourceIndexPath,
let localObject = item.dragItem.localObject as? CellModel {
collectionView.performBatchUpdates ({
data[sourceIndexPath.section].remove(at: sourceIndexPath.item)
data[destinationIndexPath.section].insert(localObject, at: destinationIndexPath.item)
collectionView.deleteItems(at: [sourceIndexPath])
collectionView.insertItems(at: [destinationIndexPath])
})
}
}
private func copyItems(coordinator: UICollectionViewDropCoordinator, destinationIndexPath: IndexPath, collectionView: UICollectionView) {
collectionView.performBatchUpdates({
var indexPaths = [IndexPath]()
for (index, item) in coordinator.items.enumerated() {
if let localObject = item.dragItem.localObject as? CellModel {
let indexPath = IndexPath(row: destinationIndexPath.row + index, section: destinationIndexPath.section)
data[indexPath.section].insert(localObject, at: indexPath.row)
indexPaths.append(indexPath)
}
}
collectionView.insertItems(at: indexPaths)
})
}
}
Cells
import UIKit
class CollectionViewCell: UICollectionViewCell {
weak var label: UILabel?
override init(frame: CGRect) {
super.init(frame: frame)
clipsToBounds = true
let label = UILabel(frame: .zero)
label.contentMode = .scaleAspectFill
addSubview(label)
label.translatesAutoresizingMaskIntoConstraints = false
label.topAnchor.constraint(equalTo: topAnchor).isActive = true
label.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
label.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
label.rightAnchor.constraint(equalTo: rightAnchor).isActive = true
label.textAlignment = .center
label.textColor = .white
self.label = label
layer.borderWidth = 1
layer.borderColor = UIColor.white.cgColor
backgroundColor = .white
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override func prepareForReuse() {
super.prepareForReuse()
label?.text = nil
backgroundColor = .white
}
}
import UIKit
class SupplementaryView: UICollectionReusableView {
weak var label: UILabel?
override init(frame: CGRect) {
super.init(frame: frame)
backgroundColor = UIColor.blue.withAlphaComponent(0.7)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
}
Result
