please bear with me as I am new to swift programming.
I have a myCollectionViewController that is a subclass of UICollectionViewController. The cells for the MyCollectionViewController are a class of MyCollectionViewCell, which is a custom UICollectionViewCell.
What I am trying to do is change the background of the MyCollectionViewCell based on the user selection AND have this selection persist when the user scrolls to other cells of the MyCollectionViewController. I have tried two ways to do this, and so far both have failed.
The first way was to write code in the didSelectItemAt method of the MyCollectionViewController:
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "myCell", for: indexPath) as! MyCollectionViewCell
cell.contentView.backgroundColor = UIColor.red
}
However, this did not work and the cell colour was not changed.
The other way I tried to do this was by changing the isSelected property of the MyCollectionViewCell.
override var isSelected: Bool {
// Change what happens when the user selects a cell
didSet {
if self.isSelected {
self.contentView.backgroundColor = Colours.primary
} else {
self.contentView.backgroundColor = Colours.secondary
}
}
}
Although this worked, the selection did not persist. That is when the user scrolled to a different cell in the collectionView and then scrolled back, the selection was gone.
Any advice would be appreciated.
Don't use dequeue in didSelectItemAt as it'll return other cell than the clicked
var allInde = [IndexPath]()
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at:indexPath) as! MyCollectionViewCell
cell.contentView.backgroundColor = UIColor.red
if !(allIndex.contains(indexPath)) {
allInde.append(indexPath)
}
}
and in cellForItem check whether indexpath to show is in the array and color it
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "id", for: indexPath as IndexPath) as! MyCollectionViewCell
if allIndex.contains(indexPath) {
cell.contentView.backgroundColor = Colours.primary
}
else {
cell.contentView.backgroundColor = Colours.secondary
}
}
// se here updated code
SPRAIN
Related
How to change the color of view in collection view when it select and when the select the other view before view came to original color How to set it?
You can use the didSelectItemAtIndexPath method and the didDeselectItemAtIndexPath method from the UICollectionViewDelegate protocol. UICollectionViewDelegate is an Objective-C protocol, indicated by #objc, that allows you to have optional methods like didSelectItemAtIndexPath and didDeselectItemAtIndexPath that you can choose to implement optionally in your delegate.
When UICollectionView gets instantiated initially, it goes through all the available methods you've implemented in the instance of UICollectionViewDelegate with responds(to:), which takes a selector parameter and returns a bool, to see which methods from the UICollectionViewDelegate protocol you've implemented without actually sending a message to them. As it detects the following methods, it remembers them and calls those methods whenever you select or deselect a cell from the collection view:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
if let indexPaths = collectionView.indexPathsForSelectedItems, let firstIndex = indexPaths.first {
cell.backgroundColor = firstIndex == indexPath ? .white : .gray
}
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) {
cell.backgroundColor = .white
}
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
guard let cell = collectionView.cellForItem(at: indexPath) else {
return
}
cell.backgroundColor = .gray
}
Alternatively, you can use the collectionView(_:didHighlightItemAt:) method and the collectionView(_:didUnhighlightItemAt:) method. The following sample code is from here:
func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) {
cell.contentView.backgroundColor = #colorLiteral(red: 1, green: 0.4932718873, blue: 0.4739984274, alpha: 1)
}
}
func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) {
cell.contentView.backgroundColor = nil
}
}
You can simply add two methods for changing colour of the view or cell in the collectionView:-
//When cell got selected
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath){
cell.backgroundColor = .green
}
}
//When cell deselected
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath){
cell.backgroundColor = .clear
}
}
If you have view inside your cell as backgroundView then you can use same functions and just need to replace cell.backgroundView.backgroundColor in place of the cell.backgroundColor. Just remember "backgroundView" is the name of the view you have inside cell.
If you want more information about this then you can follow below attached links:-
1). https://www.tutorialfor.com/questions-296884.html
2). https://en.it1352.com/article/fccf358a040b4ddba872d7324602754c.html
I have a variabel selectedIndexPath, which gets the indexPath selected from previous view controller. I am getting the required backgroundColor for cell in the collection view of present view controller. But when I select another cell in the collection view, the selected cell of previous view controller remains same without being deselected. So, now I have two cells with the background color. Following is my code
var selectedIndexPath = IndexPath()
override func viewDidLoad() {
super.viewDidLoad()
self.collectionView.allowsMultipleSelection = false
self.collectionView.allowsSelection = true
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! TestCollectionViewCell
if (indexPath == selectedIndexPath)
{
cell.backgroundColor = UIColor.white
}
else
{
cell.backgroundColor = UIColor.clear
}
collectionView.allowsMultipleSelection = false
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
{
let cell = collectionView.cellForItem(at: indexPath)
cell?.backgroundColor = UIColor.white
collectionView.allowsMultipleSelection = false
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath)
{
let cell = collectionView.cellForItem(at: indexPath)
cell?.backgroundColor = UIColor.clear
collectionView.allowsMultipleSelection = false
}
How do I deselect the cell in cellForItemAt, when I select new cell in didSelectItemAt. Thanks in advance.
First of all set allowsMultipleSelection in Interface Builder and remove all redundant occurrences of setting it in code
You have to update the selectedIndexPath variable. Manipulating the cell directly is always a bad idea.
Reloading the cells is much more reliable.
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
{
guard selectedIndexPath != indexPath else { return }
let indexPathsToUpdate = [selectedIndexPath, indexPath]
selectedIndexPath = indexPath
tableView.reloadRows(at: indexPathsToUpdate, with: .none)
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath)
{
guard selectedIndexPath == indexPath else { return }
selectedIndexPath = IndexPath()
tableView.reloadRows(at: [indexPath], with: .none)
}
There is only one problem: If you want to have an empty selection you have to declare selectedIndexPath as optional and handle it properly.
First of all, you don't need to override didDeselect for this. All you need to do is deselect the previously selected item while selecting the current item in didSelectItem. For that you can choose to maintain states in the cell as:
func changeToSelectedState() {
self.backgroundColor = UIColor.white
}
func changeToUnselectedState() {
self.backgroundColor = UIColor.clear
}
Or you can choose to write the same in the controller itself. And then you need to perform the deselection and selection in the following manner.
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
{
let previousSelectedCell = collectionView.cellForItem(at: selectedIndexPath)
previousSelectedCell.changeToUnselectedState()
let currentCell = collectionView.cellForItem(at: indexPath)
currentCell.changeToSelectedState()
selectedIndexPath = indexPath
}
I am trying on my viewDidLoad() to fetch images from my DB and then present the images, and highlight the first one.
My code thus far is:
profile?.fetchImages(onComplete: { (errors, images) in
for error in errors {
print("Error", error)
}
for imageMap in images {
self.photos.append(imageMap.value)
}
if self.photos.count < self.MAX_PHOTOS {
self.photos.append(self.EMPTY_IMAGE)
}
DispatchQueue.main.async {
self.photoCollectionView.reloadData()
}
self.updateSlideshowImages()
let indexPath = IndexPath(row: 0, section: 0)
let cell = self.photoCollectionView.cellForItem(at: indexPath)
if cell != nil {
self.setBorder(cell!)
}
})
However, for me cell is always nil, despite images existing and being fetched, and thus the setBorder is never called. Why is the cell always nil? I just want to set the border on the first cell.
You have placed self.photoCollectionView.reloadData() in async block so the let cell = self.photoCollectionView.cellForItem(at: indexPath) will run immediately before collection view reload, thats the reason you are getting nil for first cell.
You need to make sure that after collection view reload, I mean when all collection view cells are loaded then you can get and do your operations.
Alternatively, you can do this in cellForItemAtIndexPath like below...
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: CellIdentifier.jobCollectionViewCellIdentifier, for: indexPath) as! <#Your UICollectionViewCell#>
if indexPath.section == 0 && indexPath.row == 0 {
//highlight cell here
}
return cell
}
And if you want to highlight cell after all images load in collection view then you need to check for datasource of collection view.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = ...
if indexPath.row == arrImages.count-1 {
let newIndexPath = IndexPath(row: 0, section: 0)
if let cellImg = self.photoCollectionView.cellForItem(at: newIndexPath) {
self.setBorder(cellImg)
}
}
}
Instead of highlighting the UICollectionViewCell in viewDidLoad() after receiving the response, highlight it in willDisplay delegate method, i.e.
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath)
{
if indexPath.row == 0
{
cell.isHighlighted = true
}
}
And add border of cell in the isHighlighted property of UICollectionViewCell according to the cell highlight status, i.e.
class CustomCell: UICollectionViewCell
{
override var isHighlighted: Bool{
didSet{
self.layer.borderWidth = self.isHighlighted ? 2.0 : 0.0
}
}
}
You can use isSelected property the same way in case you want to change appearance of the cell based on the selection status.
Let me know if you still face any issue.
Set your cell's border in cellForRow method.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellIdentifier", for: indexPath) as! YourCustomCell
if indexPath.row == 0 {
self.setBorder(cell)
}
return cell
}
I have UICollectionView 2 rows 10+ cells.
deselected by default. when I click it becomes selected but when I click again not deselect.
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
print(indexPath)
let cell = collectionView.cellForItem(at: indexPath)
let collectionActive: UIImageView = {
let image=UIImageView(image: #imageLiteral(resourceName: "collectionActive"))
image.contentMode = .scaleAspectFill
return image
}()
let collectionInactive: UIImageView = {
let image=UIImageView(image: #imageLiteral(resourceName: "collectionInactive"))
image.contentMode = .scaleAspectFill
return image
}()
if cell?.isSelected == true {
cell?.backgroundView = collectionActive
}else{
cell?.backgroundView = collectionInactive
}
}
how fix that problem?
in viewDidLoad()
collectionView.allowsMultipleSelection = true;
afterword I implemented these methods
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
let cell = collectionView.cellForItemAtIndexPath(indexPath) as! MyCell
cell.toggleSelected()
}
func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
let cell = collectionView.cellForItemAtIndexPath(indexPath) as! MyCell
cell.toggleSelected()
}
finally in my class
class MyCell : UICollectionViewCell {
func toggleSelected ()
{
if (selected){
backgroundColor = UIColor.redColor()
}else {
backgroundColor = UIColor.whiteColor()
}
}
}
For Swift 5 +
in viewDidLoad()
collectionView.allowsMultipleSelection = true
afterword I implemented these methods
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at: indexPath) as! MovieDetailsDateCollectionViewCell
cell.toggleSelected()
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at: indexPath) as! MovieDetailsDateCollectionViewCell
cell.toggleSelected()
}
In TableView Cell class
class MyCell : UICollectionViewCell {
func toggleSelected ()
{
if (isSelected){
backgroundColor = .red
}else {
backgroundColor = .white
}
}
}
If you don't want to enable multiple selection and only want one cell to be selected at a time, you can use the following delegate instead:
If the cell is selected then this deselects all cells, otherwise if the cell is not selected, it selects it as normal.
func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
let cell = collectionView.cellForItem(at: indexPath) as! CustomCell
if cell.isSelected {
collectionView.selectItem(at: nil, animated: true, scrollPosition: [])
return false
}
return true
}
According to UICollectionView class doc, you can use:
var selectedBackgroundView: UIView? { get set }
You can use this view to give the cell a custom appearance when it is selected. When the cell is selected, this view is layered above the backgroundView and behind the contentView.
In your example in the cellForItem(at indexPath: IndexPath) -> UICollectionViewCell? function you can set:
cell.backgroundView = collectionInactive
cell.selectedBackgroundView = collectionActive
If the cell is selected, just set cell.isSelected = false in shouldSelectItemAt delegate and in a DispatchQueue.main.async { } block. So the state is actually changed to false (very) soon after the shouldSelectItemAt has been executed.
It may look like a hack but it actually works.
func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
if let cell = collectionView.cellForItem(at: indexPath), cell.isSelected {
DispatchQueue.main.async { // change the isSelected state on next tick of the ui thread clock
cell.isSelected = false
self.collectionView(collectionView, didDeselectItemAt: indexPath)
}
return false
}
return true
}
Please let me know if you find/know any cons to do this. Thanks 🙏
In iOS 14 and newer, you can set the backgroundConfiguration property of a cell. Once set, all necessary visual effects for selecting and deselecting works automatically. You can use one of the preconfigured configurations, like this:
cell.backgroundConfiguration = .listSidebarCell()
…or create a UIBackgroundConfiguration object from scratch. You can also change a preconfigured configuration before applying.
More info here: https://developer.apple.com/documentation/uikit/uibackgroundconfiguration
Im using UIcollection view as my tabbar
when I scroll collection view horizontally previous selected cell will not deselect when i select new one
this is my code to change colour when i select a cell and deselect a cell
var selectedIndexPath : IndexPath = []
func collectionView(_ collectionView: UICollectionView,
didSelectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) as?
BottomCollectionViewCell {
cell.contentView.backgroundColor = UIColor.orange
cell.backgroundColor = UIColor.orange
}
if let preViousSelectedcell = collectionView.cellForItem(at:
selectedIndexPath) as? BottomCollectionViewCell {
preViousSelectedcell.contentView.backgroundColor=UIColor.purple
preViousSelectedcell.backgroundColor = UIColor.purple
}
selectedIndexPath = indexPath
}
while scrolling cells are reused that time cellForItemAt will call so you need to change some modification in your code
func collectionView(_ collectionView: UICollectionView,
didSelectItemAt indexPath: IndexPath) {
selectedIndexPath = indexPath
YOUR_COLLECTION_VIEW.reloadData()
}
and add below lines inside your collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath)
if indexPath == selectedIndexPath {
cell.contentView.backgroundColor=UIColor.purple
cell.backgroundColor = UIColor.purple
} else {
cell.contentView.backgroundColor = UIColor.orange
cell.backgroundColor = UIColor.orange
}
Hope this will help you