How to preselect and highlight a cell from a UICollectionView - ios

Question

I've an array where I've position of previously selected cells.
I'd like to show to the user the cells that were previously selected (at another moment, can be months ago) by highlighting them and selecting them (if I click on one previously selected I'd like that it unselect it) when my popover appears, as I did in :
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
I tried different things like :
if (indexPath.row == 0 && indexPath.section == 0){
collectionView.selectItem(at: indexPath, animated: false, scrollPosition: UICollectionViewScrollPosition.centeredHorizontally)
}
Or :
let indexPathForFirstRow = IndexPath(item: 0, section: 0)
collectionView.cellForItem(at: indexPathForFirstRow)?.isSelected = true
But nothing worked (Or I couldn't see it...)
Have you any help to bring on this?
Thanks!
EDIT:
Here is what I do now:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
// get a reference to our storyboard cell
var cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! MyCollectionViewCell
// Use the outlet in our custom class to get a reference to the UILabel in the cell
if (swipeDown![2][0] == (settings!.rowSelect) && indexPath.row == 4 && indexPath.section == 4) {
let indexPathspec = IndexPath(row: 4, section: 4)
var cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPathspec) as! MyCollectionViewCell
cell.isSelected = true
cell.myLabel.text = self.items[indexPath.item]
//cell.backgroundColor = UIColor(red:0.13, green:0.37, blue:0.58, alpha:0.7)
cell.layer.borderColor = UIColor.black.cgColor
cell.layer.borderWidth = 2
print("test")
return cell
}
cell.myLabel.text = self.items[indexPath.item]
cell.backgroundColor = UIColor(red:0.13, green:0.37, blue:0.58, alpha:0.7)
cell.layer.borderColor = UIColor.black.cgColor
cell.layer.borderWidth = 2
print(cell.isSelected)
print("11")
return cell
}
With this in MyCollectionViewCell
import UIKit
class MyCollectionViewCell: UICollectionViewCell {
#IBOutlet weak var myLabel: UILabel!
override var isSelected: Bool{
didSet{
//super.isSelected = true
self.contentView.backgroundColor = self.isSelected ? .blue : .green
}
}
}
The cell is in blue, so it's selected, but I can't unselect it once it's done.
No problem for the cells I select after the launch, I can select and deselect them without problem.

Answer 1

For what you are trying to do, use isSelected property of UICollectionViewCell.
On how isSelected works, refer to: https://medium.com/#p.gpt10/uicollectionviewcell-selection-made-easy-41dae148379d
For initially selecting a UICollectionViewCell use,
self.contentCollectionView.selectItem(at: IndexPath(row: 0, section: 0), animated: true, scrollPosition: .left)
Also, in didSelectItemAt method, you don't need to change isSelected or call above method. Just refer to the above tutorial and you will get everything you need.
Edit:
class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate
{
#IBOutlet weak var aCollectionView: UICollectionView!
override func viewDidLoad()
{
super.viewDidLoad()
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
return 10
}
func numberOfSections(in collectionView: UICollectionView) -> Int
{
collectionView.allowsMultipleSelection = true
return 1
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "aCell", for: indexPath as IndexPath) as! myCollectionViewCell
cell.myLabel.text = "ok"
cell.isSelected = false
cell.layer.borderColor = UIColor.black.cgColor
cell.layer.borderWidth = 2
if indexPath.row == 5
{
collectionView.selectItem(at: indexPath, animated: true, scrollPosition: .left) //Add this line
cell.isSelected = true
}
return cell
}
override func didReceiveMemoryWarning()
{
super.didReceiveMemoryWarning()
}
}
class myCollectionViewCell: UICollectionViewCell
{
#IBOutlet weak var myLabel: UILabel!
override var isSelected: Bool{
didSet{
if self.isSelected
{
super.isSelected = true
self.contentView.backgroundColor = UIColor(red:0.08, green:0.28, blue:0.45, alpha:1)
}
else
{
super.isSelected = false
self.contentView.backgroundColor = UIColor(red:0.13, green:0.37, blue:0.58, alpha:0.7)
}
}
}
}

Answer 2

I have done some stuff for you, i hope it will help to you :
declare variables :
var selectIndex = 0
var selectIndexSec = 0
in viewDidload() :
collectionview.scrollToItem(at: IndexPath(item: selectIndex, section: selectIndexSec) , at: .centeredHorizontally, animated: false)
in collectionview delegate :
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! CustomCollectionViewCell
if selectIndexSec == (indexPath as NSIndexPath).section
{
if selectIndex == (indexPath as NSIndexPath).row
{
cell.isSelected=true
}
else
{
cell.isSelected=false
}
}
else
{
cell.isSelected=false
}
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
{
selectIndex = (indexPath as NSIndexPath).row
selectIndexSec = (indexPath as NSIndexPath).section
collectionview.reloadData()
}