I have a collection view, and you can select the items in it and toggle them on and off by changing the background colour. The cells are toggled on/off thanks to a boolean I have in an arrow I made for all of the cells. I have saved the bool value but when I try to write them back into the array and use collectionView.reloadData()the app crashes. My collectionViewcode is:
extension OLLViewController: UICollectionViewDataSource, UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { //set the amount of items in the CollectionView to the amount of items in the OLLData dictionary
return OLLData.OLLCasesList.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { //set each cell to a different mamber of the dict.
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "OLLCell", for: indexPath) as! OLLCell
cell.imageView.backgroundColor = OLLData.OLLCasesList[indexPath.item]._isSelected ? UIColor.orange : UIColor.clear //change colour if selected
let image = OLLData.OLLCasesList[indexPath.item]._imageName
cell.label.text = image
cell.imageView.image = UIImage(named: image)
let savedIsSelected = defaults.bool(forKey: Key.isSelected)
OLLData.OLLCasesList[indexPath.item]._isSelected = savedIsSelected
//collectionView.reloadData() //when uncommented it crashes the app
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) { //detect if case selected and reload CollectionView
let caseName = OLLData.OLLCasesList[indexPath.item]._imageName
print(caseName, OLLData.OLLCasesList[indexPath.item]._isSelected)
OLLData.OLLCasesList[indexPath.item]._isSelected = !OLLData.OLLCasesList[indexPath.item]._isSelected
defaults.set(OLLData.OLLCasesList[indexPath.item]._isSelected, forKey: Key.isSelected)
collectionView.reloadItems(at:[indexPath])
collectionView.reloadData()
if OLLData.OLLCasesList[indexPath.item]._isSelected == true { //if the item is selected, add to selectedCases array
selectedCases.append(OLLData.OLLCasesList[indexPath.item]._id)
selectedCaseNames.append(OLLData.OLLCasesList[indexPath.item]._imageName)
print(selectedCases, selectedCaseNames) //debugging
numberOfSelectedCases.text = String(selectedCases.count)
}
else if OLLData.OLLCasesList[indexPath.item]._isSelected == false { //remove from selectedCases array
selectedCases.removeAll(where: { $0 == OLLData.OLLCasesList[indexPath.item]._id })
selectedCaseNames.removeAll(where: { $0 == OLLData.OLLCasesList[indexPath.item]._imageName })
print(selectedCases, selectedCaseNames) //debugging
numberOfSelectedCases.text = String(selectedCases.count)
}
}
._isSelectedis the boolean that says whether the cell is 'toggled'.
Any ideas would be greatly appreciated.
First of all, uncommenting that line will produce an infinite loop. cellForRowAt happens because the collection view is reloading, so calling a refresh while the collection view is refreshing is no good.
So your issue is that you don't know how to display selected cells in your collection view, right?
Here's a function that fires right before the collection view is about to display a cell:
func collectionView(_ collectionView: UICollectionView,
willDisplay cell: UICollectionViewCell,
forItemAt indexPath: IndexPath)
{
<#code#>
}
Inside this function, you should:
Cast cell into your OLLCell (safely if you want to be thorough)
Look at your data and see if the cell should be selected OLLData.OLLCasesList[indexPath.item]._isSelected
Ask your casted cell to change its colors/UI/appearance according to your ._isSelected boolean
Step 3 has a VERY important caveat. You should be changing the UI when ._isSelected is false AND when it's true. Because the collection view reuses cells, old UI state will randomly recur. So setting it every time is a good way to ensure the behavior you want.
Here's an example:
func collectionView(_ collectionView: UICollectionView,
willDisplay cell: UICollectionViewCell,
forItemAt indexPath: IndexPath)
{
//Cast the vanilla cell into your custom cell so you have access
//to OLLCell's specific functions and properties.
//Also make sure the indexPath falls in the indices of your data
if let myCastedCell = cell as? OLLCell,
0 ..< OLLData.OLLCasesList.count ~= indexPath.item
{
myCastedCell.imageView.backgroundColor = OLLData
.OLLCasesList[indexPath.item]._isSelected
? UIColor.orange
: UIColor.clear
}
}
Related
I make a custom calendar using UICollectionView. From the calendar when I selected some dates and move forward to next month, then back again to the previous month, the selected item is deselected. Maybe it happens for reusable cell. How can I solve this problem.
For better understand what I want:
From September I select 4,5 then move to August/July/November (In this month maybe select some other dates or not)
Then return to September. In September I want to showed 4,5 as selected
I tried this using didSelectItemAt indexPath, but when return back to the September the selected item is deselected
public func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) as? CalendarDateRangePickerCell {
if cell.isSelected == true {
cell.backgroundColor = .blue
cell.label.textColor = .white
cell.isUserInteractionEnabled = true
}
selectedDate = cell.date!
}
}
First create an array of selected Cells. If you are using a model to set data to cell, you can create an array of selected models. or you can create an array of selected rows.
Let's say you are using a model.
var selectedDates: [DateModel] = []
Then
public func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) as? CalendarDateRangePickerCell {
selectedDate = cell.date!
if !selectedDates.contains(dataSourceModel[indexPath.row]) {
selectedDates.append(dataSourceModel[indexPath.row])
}
}
}
then in your cellForItem
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if selectedDates.contains(dataSourceModel[indexPath.row]) {
cell.isSelected = true
}
}
Also make sure you remove you model when unSelected
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
if selectedDates.contains(dataSourceModel[indexPath.row]) {
selectedDates.remove(dataSourceModel[indexPath.row])
}
}
*may contain some syntax error, but you can follow this path to get where you want.
Cells in UITableView and UICollectionView are reused when you scroll, that is why you should store which days selected in another place. Then, in cellForItem you should set isSelected.
Have you tried setting clearsSelectionOnViewWillAppear to false in viewDidLoad()?
A Boolean value indicating if the controller clears the selection when the collection view appears.
The default value of this property is true. When true, the collection view controller clears the collection view’s current selection when it receives a viewWillAppear(_:) message. Setting this property to false preserves the selection.
Source: Apple Developer Documentation
I have a Horizontal UICollectionView like the horizontal Calender in iOS.
Paging is enabled but not allowsMultipleSelection.
self.allowsMultipleSelection = false
self.isPagingEnabled = true
There are only 5 cells per page.
let cellSize = CGSize(width: self.view.frame.width / 5 , height: 60)
CollectionView's height is also 60.
didSelectItemAt change background color to .red and didDeselectItem resets it to .white.
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at: indexPath)
if let cell = cell {
cell.backgroundColor = .red
}
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at: indexPath)
if let cell = cell {
cell.backgroundColor = .white
}
}
The collection view has multiple sections and rows. If I select a cell in the first visible page and scroll, random cells are selected in the next visible pages. That is to say random cells are red in the next pages. I do not want this to be so. I want to select/change color of cells manually.
How can I fix this?
Don't forget that UICollectionView has embedded reusing mechanism, so you should deselect your cells in the method "prepareToReuse" directly inside the cell class.
Take a class-level variable, say index
var index = -1
As you have said that multiple selections are not allowed so the following will do the job for you
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
index = indexPath.item
collectionView.reloadData()
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at: indexPath)
if let cell = cell {
cell.backgroundColor = indexPath.item == index ? .red : .white
}
}
Whenever user tap on any cell we save the position in index variable and then call the reloadData() to notify collectionView about the change
In cellForRowAt we check if the current cell us selected we set the color to red otherwise white
First, if you want to preserve multiple selection, you have to remember your selected ones in an array since it would get lost if a cell gets recycled and reused. For that use something like a [IndexPath] type). If one selected cell is enough, you could use a non-array version of below code.
var selectedItems: [IndexPath] = []
Then, do your recoloring in your cell's cellForItemAt(:):
cell.backgroundColor = selectedItems.contains(indexPath) ? .red : .white
Your didSelectItemAt delegate function should look like:
if !selectedItems.contains(indexPath) { selectedItems.append(indexPath)}
collectionView.cellForItem(at: indexPath)?.backgroundColor = .red
and your didDeselectItemAt delegate function:
if let index = selectedItems.firstIndex(of: indexPath) { selectedItems.remove(at: index) }
collectionView.cellForItem(at: indexPath)?.backgroundColor = .white
This should actually work. Let me know if we have to do adjustments.
I'm new to swift and building iOS Application from the scratch (using swift 4) and want to do something like below.
1. Implement Multiple cell selections in UICollectionView,
2. Pass selected cells data to Server.
Please anyone can help me, how to do that? Tell me the process and supporting articles to do that.
Below is reference Image. Thanks in Advance.
Well, the best way to handle multiple selections in UICollectionView
Enable Multiple Selection
myCollectionView.allowsMultipleSelection = true
put this code in your cell awakeFromNib
override func awakeFromNib() {
super.awakeFromNib()
let view = UIView(frame: bounds)
self.backgroundView = view
let coloredView = UIView(frame: bounds)
coloredView.backgroundColor = UIColor.red
self.selectedBackgroundView = coloredView
}
you can get the selected indexPath items
let items = myCollectionView.indexPathsForSelectedItems
This basic example. You can change as per your data.
When you select any cell then you need to check that selected cell is already selected before or not.
If not then add selected cell indexPath in indexArray and selected cell value in valueArray.
If current selected cell is previously selected then remove indexPath from indexArray and also remove selected cell value from valueArray
on continue button press pass arrSelectedData to server or next screen.
Define below 3 array.
var arrData = [String]() // This is your data array
var arrSelectedIndex = [IndexPath]() // This is selected cell Index array
var arrSelectedData = [String]() // This is selected cell data array
//UICollectionView Delegate & DataSource
extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout
{
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return self.arrData.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell : CollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "CollectionViewCell", for: indexPath) as! CollectionViewCell
if arrSelectedIndex.contains(indexPath) { // You need to check wether selected index array contain current index if yes then change the color
cell.vw.backgroundColor = UIColor.red
}
else {
cell.vw.backgroundColor = UIColor.lightGray
}
cell.layoutSubviews()
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 100, height: 100)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
print("You selected cell #\(indexPath.item)!")
let strData = arrData[indexPath.item]
if arrSelectedIndex.contains(indexPath) {
arrSelectedIndex = arrSelectedIndex.filter { $0 != indexPath}
arrSelectedData = arrSelectedData.filter { $0 != strData}
}
else {
arrSelectedIndex.append(indexPath)
arrSelectedData.append(strData)
}
collectionView.reloadData()
}
}
You can write the code like this to Enable Multiple Selection :-
yourCollectionViewName.allowsMultipleSelection = true
then you can Do it like this to see the cell Selected -
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
var cell = collectionView.cellForItemAtIndexPath(indexPath)
if cell?.selected == true {
cell?.backgroundColor = UIColor.orangeColor()
}
}
To Deselect You can do something Like this -
func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
var cell = collectionView.cellForItemAtIndexPath(indexPath)
cell?.backgroundColor = UIColor.clearColor()
}
Enable Multiple Selection
collectionView.allowsMultipleSelection = true
Overrider isSelected property of collectionViewCell.
override var isSelected: Bool {
didSet {
if self.isSelected {
//You can change this method according to your need.
setSelected()
}
else {
//You can change this method according to your need.
setUnselected()
}
}
}
func setSelected(){
bgView.layer.borderWidth = 4
bgView.layer.borderColor = UIColor.Palette.darkBlue.cgColor
bgView.backgroundColor = .blue.withAlphaComponent(0.2)
}
func setUnselected(){
bgView.layer.borderWidth = 0
bgView.backgroundColor = .white
}
You can print selected cell's indexPath
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
print(collectionView.indexPathsForSelectedItems)
}
Well, to achieve a thing like that, you need to mainly perform the following tasks
Whenever user clicks on a particular cell, you need to change the background colour for that item in the didSelectItemAt delegate method of UICollectionView
Now to send that data to server, you need an array to store all the selected cells and then send that array to server . You can perform the same in didSelectItemAt method as well
I can show you a prototype of what the function will look like:
Let's assume you have an array named arrayForPopulating for populating data inside Collection View and we have array named finalSelections which consist of names of all the selections that user made
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at: indexPath)
// Change the background colour of the cell here
cell.contentView.backgroundColor = UIColor.red
// Add the selected cell's data to the array
finalSelections.append(arrayForPopulating[indexPath.row])
}
Now you can send you finalSelections array to the server !
I have an odd problem with my UICollectionView. When I select the first cell in my Collection View the last cell is highlighted but does not show up in the array of selected index paths. Why is this happening?
Here is the code I am using to select and deselect the cells?
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
// handle tap events
print("You selected cell #\(indexPath.item)!")
let cell = collectionView.cellForItem(at: indexPath)
cell?.layer.borderWidth = highlightedCellBorderWidth
cell?.layer.borderColor = UIColor.yellow.cgColor
selectedImages.append(imageArray[indexPath.item])
print(selectedImages)
print(collectionView.indexPathsForSelectedItems)
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at: indexPath)
cell?.layer.borderWidth = 0
let index = selectedImages.index(of: imageArray[indexPath.item])
selectedImages.remove(at: index!)
print(selectedImages)
print(collectionView.indexPathsForSelectedItems)
}
You don't show how your cell is initialized, but...
collectionView(_:didDeselectItemAt:) is only called when the user successfully deselects an item. It does not get called if you deselect an item programmatically. If you are not resetting your layer's borderWidth when initializing a cell, the non-zero width will carry forward when the cell is reused by the collection view.
I found this link on S.O. which was helpful. To solve the problem I simply added the following code to my func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {}.
Code...
if collectionView.indexPathsForSelectedItems?.contains(indexPath) == true {
print("This cell is selected \(indexPath.item)")
cell?.layer.borderWidth = 3
cell?.layer.borderColor = UIColor.yellow.cgColor
}else{
cell?.layer.borderWidth = 0
}
I have inserted a collectionView inside my tableViewCell. Tableview contains the list of categories and the collectionView contains all the product. How can I have a different number of items in the collectionView based off of which table view row was selected? I've tried storing the selected table view row and using that to define the number of items to be returned however it either crashes with no error code, tells me the value is nil or just does not display any clitems in the collectionView. Any help would be greatly appreciated. Thank you for your time.
Below is my code:
My Custom table view cell:
extension ExpandableCell: UICollectionViewDelegate, UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
let toReturn = categoryItems.count
return counter
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
//
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CollectionCell", for: indexPath) as! CustomCollectionViewCell
//What is this CustomCollectionCell? Create a CustomCell with SubClass of UICollectionViewCell
//Load images w.r.t IndexPath
print(self.selectedCategory.description)
let newArray = starbucksMenu[selectedCategory]
//cell.image.image = UIImage(named: (allItems[selectedCategory]?[indexPath.row])!)
cell.label.text = categoryItems[indexPath.row]
//cell.layer.borderWidth = 0.1
return cell
}
My table view delegate method:
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
print(indexPath.row)
word = indexPath.row
guard let cell = tableView.cellForRow(at: indexPath) as? ExpandableCell
else { return }
switch cell.isExpanded
{
case true:
self.expandedRows.remove(indexPath.row)
self.selectedCategory = ""
case false:
self.expandedRows.insert(indexPath.row)
}
self.selectedCategory = categories[indexPath.row]
print(self.selectedCategory)
//self.array = starbucksMenu[starbucksMenuCategories[indexPath.row]]!
//self.collectionView.reloadData()
cell.menuItems = allItems[selectedCategory]!
cell.categoryItems = allItems[selectedCategory]!
cell.isExpanded = !cell.isExpanded
self.itemsArray = allItems[selectedCategory]!
self.tableView.beginUpdates()
self.tableView.endUpdates()
}
I've tried many things, I've tried adding the items in an array and returning the count (displays nothing). I have a dictionary with the necessary items so I've also tried returning allItems[selectedCategory]?.count and this always returns an error, I believe selectedCategory has no value once this is called.
Make a for loop of collection view item with appropriate operation Between beginUpdate() and endUpdate()