I can't understand what I am doing wrong. I have a UITableView called TblView_Categorie, what I am trying to do is get the cell at desired indexpath:
Here is my code:
let myRecordindex = IndexPath(row: myRecordcheck, section: 0)
let cell = tblViewcategorie.cellForRow(at: myRecordindex) as! categorieTVC
The problem is if MyRecordIndex is shown screen (no scrolling needed) everything working fine
If MyRecordIndex is not shown on screen (scrolling needed) I have this error:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
If I manually scroll to the desired index and I enter the desired MyRecordIndex everything working fine
I tried to automatically scrolling using the code below: the scroll work but still same error
self.tblViewCategorie.scrollToRow(at: myRecordindex, at: UITableViewScrollPosition.middle, animated: true)
Why I have this error? All I am trying to do is getting the cell at desired indexpath to change color, font, etc.
// UPDATE cellForRowAt Implementation
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") as! categorieTVC
if let categorieName = self.fetchedResultsController.object(at: indexPath).categorieName{
cell.setListeDesCategories(categorieName: categorieName)
}
return cell
}
// Update code and crash screen shot
You can't explicit unwarp
let cell = TblView_Categorie.cellForRow(at: MyRecordIndex) as! CategorieTVC
as cell my be not visible so it will be nil -> crash
try
let cell = TblView_Categorie.cellForRow(at: MyRecordIndex) as? CategorieTVC
if(cell != nil)
{
}
Edit : scroll to the cell and dispatch after the cellForRow
let myRecordindex = IndexPath(row: myRecordcheck, section: 0)
self.tblViewCategorie.scrollToRow(at: myRecordindex, at: UITableViewScrollPosition.middle, animated: true)
DispatchQueue.main.asyncAfter(deadline: .now() + 1.0 )) {
let cell = TblView_Categorie.cellForRow(at: MyRecordIndex) as? CategorieTVC
if(cell != nil)
{
}
}
Related
I've seen everywhere that it's bad practice to iterate through a tableView but I'm afraid I have no other alternative. I want to have the AVSpeechSynthesizer read the content of the labels that are inside my custom UITableViewCells.
Of course, this could be done directly using the source array of the tableView but the problem is that I want to have the synthesiser read the labels and at the same time highlight the words that are being spoken.
I have done some tests but the problem is that as the cells are being reused by the table view, I end up with empty cells...
What is the right way of ensuring my cells are not empty ?
I've tried scrolling the tableView to ensure the cells aren't empty but it doesn't work either.
Here is my code so far ...
func scrollToRow(rowToGo: Int) {
self.collectionView.scrollToItem(at: self.indexPath as IndexPath, at: .centeredVertically, animated: true)
let colorCell = self.collectionView.dequeueReusableCell(withReuseIdentifier: "ColorCell", for:indexPath as IndexPath ) as! ColorCell
let myString = colorCell.colorLabel.text!
print(myString)
self.speakString(sender: self, str:(myString))
}
#IBAction func playPauseButton(_ sender: UIButton) {
if !self.speechSynthesizer.isSpeaking{
let btnImage = UIImage(named: "pausedButton.png")
self.playPauseButton.setImage(btnImage , for: UIControlState.normal)
self.isPaused = false
// var indexPath:Double = 0
self.indexPath = NSIndexPath(row: 0, section: 0)
for i in 0...36 {
print(i)
self.indexPath = NSIndexPath(row: i, section:0)
self.scrollToRow(rowToGo:i)
// self.indexPath = NSIndexPath(index:i)
// self.collectionView.selectItem(at: indexPath as IndexPath, animated: true, scrollPosition: .centeredVertically)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt
indexPath: IndexPath) -> UICollectionViewCell {
let myCell = collectionView.dequeueReusableCell(withReuseIdentifier:
"ColorCell", for: indexPath) as! ColorCell
myCell.colorLabel.text = self.wordList[indexPath.row]
myCell.colorImage.image = self.images[indexPath.row]
return myCell }
My collectionView is displayed correctly and all my labels inside the UICollectionViewCells contain text. However, when I press the play button, the first time, nothing gets spoken. If I scroll back and press again, only 3 or 4 cells actually exist and get their label.text printed and spoken while all the other indexes are empty.
Any suggestion would be welcome
Here is my code.
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell: CellAvailableJobs = self.tblJobs.dequeueReusableCell(withIdentifier: "CellAvailableJobs") as! CellAvailableJobs
let jobsNearByObj:JobsNearBy = self.jobsArray![indexPath.row]
cell.loadCell(jobsNearByObj: jobsNearByObj)
cell.btnHeart.addTarget(self, action: #selector(JobsVC.btnBookmarkAction), for: .touchUpInside)
cell.btnHeart.tag = indexPath.row
return cell
}
#IBAction func btnBookmarkAction(_ sender: AnyObject){
let button = sender as? UIButton
print("tag: \(String(describing: button?.tag))")
let cell = button?.superview?.superview as? UITableViewCell
let indexPath = tblJobs.indexPath(for: cell!)
print("bookmarkedJobId: \(String(describing: indexPath.row))")
}
I'm fetching data from web and populating them on tableview, everything is working well. I want to print indexpath.row when the button on cell is tapped. On above method the compiler is complaining that the cell is nil. This line: let indexPath = tblJobs.indexPath(for: cell!).
What is the problem with this code. How the cell is nil in this code. Can anyone help me with this issue?
The problem is when cell is currently not visible it's value is nil , you can't explicitly unwrap an optional value
let cell = button?.superview?.superview as? UITableViewCell
Try this
if(cell != nil)
{
let indexPath = tblJobs.indexPath(for: cell!)
}
beside type of cell is CellAvailableJobs and you use as? UITableViewCell
Line let cell = button?.superview?.superview as? UITableViewCell seems to fail to be the UITableViewCell instance, thus cell is nil.
As you figured out, this is what you wanted in fact:
let cell = button?.superview?.superview?.superview as? UITableViewCell
I've never run into this issue before, but here is what I am currently experiencing:
I have a UITableView in a view controller. Delegate and dataSource are setup properly.
Now I'm running into performance issues after showing/inserting a few cells.
The issue is that the tableview seems to not dequeue some of the cells but rather creates a new one each time (always calls awakeFromNib in the custom class).
The ones with which the dequeuing seems to not work are just simple ones with a label and some with a label, an image and another label.
There is however one case in which dequeuing seems to work. I have a custom cell class that just contains a vertical stack view into which I dynamically add a variable amount of custom buttons.
I have a class that is responsible for setting up the cells. It has a method for each of the cell classes I use.
func initialModeratorCell(at indexPath: IndexPath, with message: Message, in tableView: UITableView) -> OnboardingInitialModeratorCell{
guard let cell = tableView.dequeueReusableCell(withIdentifier: initalModeratorCellIndentifier) as? OnboardingInitialModeratorCell else{
fatalError("No cell with \(initalModeratorCellIndentifier) identifier")
}
if indexPath.row != 0{
cell.moderatorImage.isHidden = true
}
let attributedMessage = attributedString(for: message, with: paragraphStyleFor(message: message))
cell.mesageText.attributedText = attributedMessage
cell.dateLabel.text = message.userType.name()
cell.mesageText.sizeToFit()
cell.dateLabel.sizeToFit()
return cell
}
All those methods look similar to this. This is one that doesn't seem to get reused.
This here is the one that does get reused (awakeFromNib only called once):
func componentCell(from item: ConversationItem, in tableView: UITableView, with owner: OnboardingComponentCellDelegate) -> OnboardingComponentCell{
guard let comp = item as? Component else{
fatalError("Type of item is not Component, but should be!")
}
guard let cell = tableView.dequeueReusableCell(withIdentifier: componentButtonsCellIdentifier) as? OnboardingComponentCell else{
fatalError("No cell with \(componentButtonsCellIdentifier) identifier")
}
cell.componentStack.translatesAutoresizingMaskIntoConstraints = false
setupComponentCell(cell, for: comp, owner: owner)
return cell;
}
This is setupCell():
setupComponentCell(_ cell: OnboardingComponentCell, for comp: Component, owner: OnboardingComponentCellDelegate){
cell.reset()
cell.component = comp
OnboardingComponentManager.createComponent(for: comp, in: cell, delegate: owner)
}
The cell.reset() method looks like this:
func reset(){
component = nil
delegate = nil
componentStack.removeAll() //removeAll is in an extension on UIStackView
}
The call OnboardingComponentManager.createComponent() just populates the stackview with the correct buttons for said component.
The methods above (componentCell(from:) and initialModeratorCell(at:) are called from the public method onboardingCellForItem(at indexPath: IndexPath, ..):
static func onboardingCellForItem(at indexPath: IndexPath, with displayedItems: Items, in tableView: Table, typingDelegate: IndicatorDelegate, buttonOwner: CellDelegate, onboardingType: ConvType) -> UITableViewCell{
let item = displayedItems[indexPath.row]
if item.type == .message{
return messageCell(from: item, at: indexPath, in: tableView, with: displayedItems)
}else if item.type == .component{
return componentCell(from: item, in: tableView, with: buttonOwner)
}else if item.type == .typingIndicator{
return typingIndicatorCell(with: typingDelegate, in: tableView)
}
return UITableViewCell()
}
This method then is called from the dataSource method cellForRowAtIndexPath like this:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
return OnboardingCellManager.onboardingCellForItem(at: indexPath, with: displayedItems, in: tableView, typingDelegate: self, buttonOwner: self, onboardingType: .onboarding)
}
The cells were prototyped in a storyboard in the tableView (as prototype cells).
I'm somewhat hitting a wall here. I've never run into this issue before and I can't seem to find the reason as to why it happens.
This performance degradation is most notable on older devices (iPhone 5, etc).
I have a FollowVC and FollowCell Setup with collection View. I can display all the datas correctly into my uIcollection view cell using the following code with no problem.
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
if let cell = collectionView.dequeueReusableCellWithReuseIdentifier("FollowCell", forIndexPath: indexPath) as? FollowCell {
let post = posts[indexPath.row]
cell.configureCell(post, img: img)
if cell.selected == true {
cell.checkImg.hidden = false
} else {
cell.checkImg.hidden = true
}
return cell
}
}
Note that I could also select and deselect multiple images using the following code
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
if deletePressed == true {
let cell = collectionView.cellForItemAtIndexPath(indexPath) as! FollowCell
cell.checkImg.hidden = false
} else {
let post = posts[indexPath.row]
performSegueWithIdentifier(SEGUE_FOLLOW_TO_COMMENTVC, sender: post)
}
}
func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
let cell = collectionView.cellForItemAtIndexPath(indexPath) as! FollowCell
cell.checkImg.hidden = true
}
When In "Select" mode, I can perform the selction of each cell and a check mark will be displayed on the cell. However, what I want to do is to have a cancel buttom to disable all the selected cell and removing the checkImg.
I have tried
func clearSelection() {
print("ClearSelection posts.count = \(posts.count)")
for item in 0...posts.count - 1 {
let indexP = NSIndexPath(forItem: item, inSection: 0)
followCollectionView.deselectItemAtIndexPath(indexP, animated: true)
let cell = followCollectionView.cellForItemAtIndexPath(indexP) as! FollowCell
cell.checkImg.hidden = true
}
}
The program crashes here giving me a fatal error: Unexpectedly found nil while unwrapping an optional error at
let cell = followCollectionView.cellForItemAtIndexPath(indexP) as! FollowCell
I dont know why it is having trouble unwrapping the cell to be my FollowCell which contains an instance of the checkImg. I already used it before in a similar situation in didSelectItemAtIndexPath and it seems to work?
Thanks,
Not all of the selected cells may be on screen at the point when you are clearing the selection status, so collectionView.cellForItemAtIndexPath(indexPath) may return nil. Since you have a force downcast you will get an exception in this case.
You need to modify your code to handle the potential nil condition but you can also make your code more efficient by using the indexPathsForSelectedItems property of UICollectionView
let selectedItems = followCollectionView.indexPathsForSelectedItems
for (indexPath in selectedItems) {
followCollectionView.deselectItemAtIndexPath(indexPath, animated:true)
if let cell = followCollectionView.cellForItemAtIndexPath(indexPath) as? FollowCell {
cell.checkImg.hidden = true
}
}
Using Extension in Swift 4
extension UICollectionView {
func deselectAllItems(animated: Bool) {
guard let selectedItems = indexPathsForSelectedItems else { return }
for indexPath in selectedItems { deselectItem(at: indexPath, animated: animated) }
}
}
To simplify further, you could just do
followCollectionView.allowsSelection = false
followCollectionView.allowsSelection = true
This will in fact correctly clear your followCollectionView.indexPathsForSelectedItems even though it feels very wrong.
collectionView.indexPathsForSelectedItems?
.forEach { collectionView.deselectItem(at: $0, animated: false) }
This answer may be useful in swift 4.2
let selectedItems = followCollectionView.indexPathsForSelectedItems
for (value in selectedItems) {
followCollectionView.deselectItemAtIndexPath(value, animated:true)
if let cell = followCollectionView.cellForItemAtIndexPath(value) as? FollowCell {
cell.checkImg.hidden = true
}
}
I got it solved easier by doing this:
tableView.selectRow(at: nil, animated: true, scrollPosition: UITableView.ScrollPosition.top)
I have a table view like this:
when the user tap one row, I want uncheck the last row and check the selected row. So I wrote my code like this:
(for example my lastselected = 0)
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
var lastIndexPath:NSIndexPath = NSIndexPath(forRow: lastSelected, inSection: 0)
var lastCell = self.diceFaceTable.cellForRowAtIndexPath(lastIndexPath) as! TableViewCell
var cell = self.diceFaceTable.cellForRowAtIndexPath(indexPath) as! TableViewCell
lastCell.checkImg.image = UIImage(named: "uncheck")
cell.checkImg.image = UIImage(named: "check")
lastSelected = indexPath.row
}
every thing working fine when I tap a row without scrolling. I realize that when I run the code and scrolling the table immediately and selected the one row. My program will crash with error:
"fatal error: unexpectedly found nil while unwrapping an Optional value"
the error show in this line:
I don't know what wrong in here?
Because you are using reusable cells when you try to select a cell that is not in the screen anymore the app will crash as the cell is no long exist in memory, try this:
if let lastCell = self.diceFaceTable.cellForRowAtIndexPath(lastIndexPath) as! TableViewCell{
lastCell.checkImg.image = UIImage(named: "uncheck")
}
//update the data set from the table view with the change in the icon
//for the old and the new cell
This code will update the check box if the cell is currently in the screen. If it is not currently on the screen when you get the cell to reused (dequeuereusablecellwithidentifier) you should set it properly before display. To do so you will need to update the data set of the table view to contain the change.
Better approach will be storing whole indexPath. not only the row. Try once i think this will work. I had the same problem in one of my app.
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
var lastCell = self.diceFaceTable.cellForRowAtIndexPath(lastSelectedIndexPath) as! TableViewCell
var cell = self.diceFaceTable.cellForRowAtIndexPath(indexPath) as! TableViewCell
lastCell.checkImg.image = UIImage(named: "uncheck")
cell.checkImg.image = UIImage(named: "check")
lastSelectedIndexPath = indexPath
}
EDIT: or you can try this.
func tableView(tableView: UITableView, didDeselectRowAtIndexPath indexPath: NSIndexPath) {
var lastCell = self.diceFaceTable.cellForRowAtIndexPath(indexPath) as! TableViewCell
lastCell.checkImg.image = UIImage(named: "uncheck")
}