I have a filter operation which is done on a bottom sheet and this value is then converted to a dictionary, I have a collectionView embeded in a UIView to display filter parameters.
When an item is selected and a filter button is pressed, I want to save the selected value using UserDefault so I can persist the searched Item if the user decides to go to the filter page again until the user press rest then I clear everything.
Currently my filter works as expected but my issue now is the persistence. When I preselect the cells, and I try to deselect that field, I get a crash.
Here's what I do
fileprivate let data1 = UserDefaultsConfig.contributionTypeFilter["selectedPaymentIndex"] as? Data
var arrSelectedIndex = [IndexPath]() // This is selected cell Index array
var arrSelectedData = [String]()
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
let cell = collectionView.cellForItem(at: indexPath)
cell?.contentView.backgroundColor = UIColor.white.withAlphaComponent(0.8)
let strData = PaymentMethodFilter.allCases[indexPath.item].rawValue.capitalized
arrSelectedIndex.remove(at: indexPath.row)
arrSelectedData.remove(at: indexPath.row)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let strData = PaymentMethodFilter.allCases[indexPath.item].rawValue.capitalized
arrSelectedIndex.append(indexPath)
arrSelectedData.append(strData)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeue(dequeueableCell: PaymentMethodFilterCollectionCell.self, forIndexPath: indexPath)
cell.feedSubviews(with: PaymentMethodFilter.allCases[indexPath.row])
guard let selectedData = data1 else {
return cell
}
arrSelectedData = UserDefaultsConfig.contributionTypeFilter["payment_method_names"] as? [String] ?? []
arrSelectedIndex = NSKeyedUnarchiver.unarchiveObject(with: selectedData) as? [IndexPath] ?? []
arrSelectedIndex.forEach {
collectionView.selectItem(at: $0, animated: true, scrollPosition: .right)
}
return cell
}
Fatal error: Index out of range: file
/Library/Caches/com.apple.xbs/Sources/swiftlang/swiftlang-1103.2.25.8/swift/stdlib/public/core/Array.swift,
line 1221 2020-08-16 15:36:26.359431+0100 Riby[40882:1056506] Fatal
error: Index out of range: file
/Library/Caches/com.apple.xbs/Sources/swiftlang/swiftlang-1103.2.25.8/swift/stdlib/public/core/Array.swift,
line 1221
I want to save the selected value
To record what is selected, do not make an array of index paths, because index paths can change (and in your code, that's just what happens). Instead, make an array of unique identifiers for the data represented by the selected cells. That way, you can always find them again. What doesn't change is the data, so that's the way to identify things.
Basically, your underlying data model should consist of uniquely identifiable entries. (If you use a diffable data source, that rule will be enforced for you, which is just one many reasons why diffable data sources are great.) You can always convert between actual data objects and current cells in the collection view, in both directions.
Related
I have a ViewController that have a collectionView and I managed to make it selectable and all but the problem is that I have a checkmark image that stays in the first cell when the VC opens but in fact the cell is not selected at all and still the checkmark is there!
Code of the VC:
var selected = IndexPath(item: 0, section: 0)
var properties = connectedProperties(StatusCode: 0)
var propertiesNew = connectedProperties(StatusCode: 0)
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return properties.Result?.count ?? 0
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "dashboardCollectionViewCell", for: indexPath) as? dashboardCollectionViewCell else { return UICollectionViewCell() }
let currentPropertie = properties.Result?[indexPath.row]
cell.checkMarkButton.isHidden = !(indexPath == selected)
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let selectedCell = properties.Result?[indexPath.row]
changeCustomerKey.DefaultsKeys.keyTwo = indexPath.row
changeCustomerKey.DefaultsKeys.keyThree = selectedCell!.id!
let previous = selected.dropLast()
selected = indexPath
collectionView.reloadItems(at: [previous, selected])
}
If you want to tell your collection view to select a specific cell, you need to call the UICollectionView method selectItem(at:animated:scrollPosition:).
The "tricky bit" is that you can't call that until the collection view has finished populating itself (by calling your data source methods) and the first cell has been added to the collection view.
You might need to resort to something a bit hacky like adding an "initialDisplay" bool property who's value starts as true.
In your data source method that returns cells, check if initialDisplay==true and the requested indexPath is (0,0). If so, set initialDisplay=false, and fire a one-shot timer with a short delay. In the timer's closure, call selectItem(at:animated:scrollPosition:). The timer delay will return control to the event loop and give the system time to add the cell to the collection view.
There might be a better way to do this, but I can't think of it offhand, since you can't be sure when you will be asked to return your cell at IndexPath (0,0)
I have a collection view that is being populated with images created from parsed data. It is being populated and updated by using an NSFetchedResultsController as the data source. The code is in Swift 4, so to do so I am using the data source methods for the collection view along with the delegate methods for the NSFetchedResultsControllerDelegate as shown here:
func collectionView (_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if let count = fetchedResultsController.sections?[0].numberOfObjects {
return count
}else {
return 0
}
}
func collectionView (_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
print("Setting cell with photo")
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "photoCell", for: indexPath) as! CollectionViewCell
let photoForCell = fetchedResultsController.object(at: indexPath)
cell.cellImage.image = UIImage(data: photoForCell.imageData!)
print(photoForCell.imageData!)
return cell
}
I am trying to calculate how many images were pulled in the parsed data and use this information to temporarily populate that many cells in the collection view with the same placeholder image in all of them. Then, once the images have all been downloaded and saved the NSFetchedResultsController will trigger the data source methods to refresh and populate the collection view with the new photos instead of the placeholder photos.
I have not been able to find any videos or posts that show how to do so. I tried creating a variable that holds the count of objects in the parsed data. That variable is then used in an if statement in the (:numberOfItemsInSection:) and (:cellForItemAt:) to determine whether it should populate the collection from saved photos or using the temporary photos like this:
func collectionView (_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if self.placeHolderCount != nil {
return placeHolderCount
}
if let count = fetchedResultsController.sections?[0].numberOfObjects {
return count
}else {
return 0
}
}
func collectionView (_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
print("Setting cell with photo")
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "photoCell", for: indexPath) as! CollectionViewCell
let photoForCell = fetchedResultsController.object(at: indexPath)
if self.placeHolderCount != nil {
cell.cellImage.image = #imageLiteral(resourceName: "VirtualTourist_5112")
return cell
}
cell.cellImage.image = UIImage(data: photoForCell.imageData!)
print(photoForCell.imageData!)
return cell
}
Unfortunately, that causes the app to crash with an error saying "NSInvalidArgumentException reason: 'no object at index 0 in section at index 0"
During my troubleshooting, I found that this crash happens at the point when the view context is saved after downloading all the images. Everything in the application works perfectly including loading the downloaded images until I add the changes to the delegate methods. Does anyone know if I am on the right track? Should I be going about it in a completely different way? I have seen external libraries around that will accomplish this, but I cannot use any external libraries or frameworks for this particular application.
I got a collection view with 2 different sections. I want to tap a cell in one of the sections and pass the text in that cell to a text view, which is in a separate cell in its own section.
This is what I tried so far, but nothing happened. I am trying to send the notes data to another cell. I can print the data when the cell is tapped.
Updated: This is the cell with the text view that I want to pass the selected cell data to.
// cell that I am trying to passing data to
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = myCollectionView.dequeueReusableCell(withReuseIdentifier: "notesView", for: indexPath) as! TestViewCollectionViewCell
cell.myTextView.text = .....
return cell
}
// Cell that I am passing data from
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if indexPath.section == 0 {
// Cell that I want to send data to
let cell = myCollectionView.dequeueReusableCell(withReuseIdentifier: "notesView", for: indexPath) as! TestViewCollectionViewCell
let myNotes = notes[indexPath.row]
cell.myTextView.text = myNotes.textView
}
}
Here is the way you can correct that:
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if indexPath.section == 0 {
//First get your selected cell
if let cell = collectionView.cellForItem(at: indexPath) as? TestViewCollectionViewCell {
//Now get selected cell text here
//update your section two array with new values
//Reload your collection view.
} else {
// Error indexPath is not on screen: this should never happen.
}
}
}
I have an array of NSObjects that I need to read in another viewcontroller. However I'm unsure what level I should be setting the data for it.
This screen shot below best explains what I'm trying to do. Each HomeController has a title, members list, description and inset collectionview (yellow bar). I need the collection views number of cells to equal the number of members.
I tried creating a reference to HomeController inside the inset collectionview by using lazy var but that got the the error:
fatal error: Index out of range
lazy var homeController: HomeController = {
let hc = HomeController()
hc.liveCell = self
return hc
}()
Again this is done from within the inset collectionview
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath :
IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: profileImageCellId, for: indexPath) as! profileImageCell
let room = homeController.rooms[indexPath.row]
print(room.members?.count)
return cell
}
Any suggestions?
EDIT
Data is added to the array using this function
var rooms = [Room]()
func fetchAllRooms(){
Database.database().reference().child("rooms").observe(.childAdded, with: { (snapshot) in
if let dictionary = snapshot.value as? [String: AnyObject] {
let room = Room()
room.rid = snapshot.key
room.setValuesForKeys(dictionary)
self.rooms.append(room)
print(snapshot)
DispatchQueue.main.async(execute: {
self.collectionView?.reloadData()
})
}
print("end of room snap")
}, withCancel: nil)
}
Here is the cell for item at index path at the HomeController level
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
var cell = UICollectionViewCell()
let section = indexPath.section
let liveCell = collectionView.dequeueReusableCell(withReuseIdentifier: LiveCellId, for: indexPath) as! LiveCell
let cell = liveCell
let room = rooms[indexPath.row]
liveCell.liveStreamNameLabel.text = room.groupChatName
liveCell.descriptionLabel.text = room.groupChatDescription
return cell
}
You need to check the count of your array in order to prevent the crash Index out of range
if homeController.rooms.count > indexPath.row {
let room = homeController.rooms[indexPath.row]
print(room.members?.count)
}
Can you Debug and share below two things then we can look further on this
Check whats the index path you are getting
Check if your array have data
Hi so I'm using a side scrolling UICollectionView to display groups of people that the user makes. The groups are stored on my server and when the view loads, they load from the server. However I want the first cell to always be the same which is a cell which lets you create groups. This is the layout i need.
I know how to use multiple different custom cells, but how do I make it so the first cell is static and the cells after load content from my servers? Thanks :)
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return familyName.count
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
if indexPath.row == 0 {
let cell : AddGroupCollectionViewCell = collectionViewOutlet.dequeueReusableCellWithReuseIdentifier("Add", forIndexPath: indexPath) as! AddGroupCollectionViewCell
return cell
} else {
let cell : FriendGroupsCell = collectionViewOutlet.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as! FriendGroupsCell
cell.groupImage.image = UIImage(named: "pp")
cell.groupNameLabel.text = familyName[indexPath.row]
return cell
}
}
This is my code and it misses out the first person in the array because the index path skips over it. How can i modify this so it works
UICollectionViewCell is leveraging reusing techniques to improve performance. Remember this. Nothing can be static in a cell, because this cell later will be on another index.
You can use collectionView:cellForItemAtIndexPath: to make the first cell always load the same images/labels via indexPath.row == 0
You can use prepareReuse method to clean up the resources in the cell. So if cell No.2 is going to be the new No.1 cell, it get a chance to clean up old resources.
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell : AddGroupCollectionViewCell = collectionViewOutlet.dequeueReusableCellWithReuseIdentifier("Add", forIndexPath: indexPath) as! AddGroupCollectionViewCell
if indexPath.row == 0 {
cell.groupImage.image = UIImage(named: "new")
cell.groupNameLabel.text = "new"
} else {
cell.groupImage.image = UIImage(named: "pp")
cell.groupNameLabel.text = familyName[indexPath.row]
}
return cell
}