I'm very new to iOS development and Swift.
I have a UICollectionView that populates images from the array. My idea is to load initially 10 images and let user scroll to the bottom of the collectionView and then load next 10 images from the array by pressing button 'more' or just automatically.
Can you suggest the best way to do it?
My code is:
self.searches.insert(results, at: 0)
override func collectionView(_ collectionView: UICollectionView,
cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
//1
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier,
for: indexPath) as! CatPhotoCell
// this methods takes one photo from searches array
let flickrPhoto = photoForIndexPath(indexPath: indexPath)
cell.imageView.image = flickrPhoto.thumbnail
cell.cat_name.text = flickrPhoto.title
return cell
}
private extension CatsPhotosCollectionViewController {
func photoForIndexPath(indexPath: IndexPath) -> FlickrPhoto {
return searches[(indexPath as NSIndexPath).section].searchResults[(indexPath as IndexPath).row]
}
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView){
//step 2 here
}
1.Intially set array count as 10.
2.Increase array count whatever you want inside the above function and reload collectionView.
Related
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
}
}
I have a UICollectionView with flow layout, about 140 cells each with a simple UITextView. When a cell is recycled, I pop the textView onto a cache and reuse it later on a new cell. All works well until I reach the bottom and scroll back up. At that point I can see that the CollectionView vends cell number 85, but then before cell 85 is displayed it recycles it again for cell 87 so I now lose the content of the cell I had just prepared.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "FormCell", for: indexPath) as! FormCollectionViewCell
let textView = Cache.vendTextView()
textView.text = "\(indexPath.row)"
cell.addSubview(textView)
cell.textView = textView
return cell
}
And on the UIcollectionViewCelC
override func prepareForReuse() {
super.prepareForRuse()
self.textView.removeFromSuperView()
Cache.returnView(self.textView)
}
I would have thought that after cellForItemAtIndexPath() was called, it would then be removed from the reusable pool of cells but it seems it is immediately being recycled again for a neighbouring cell. maybe a bug or I am possibly misunderstanding the normal behaviour of UICollectionView?
As I understand it, what you're trying to do is just keep track of cell content - save it when cell disappears and restore it when it comes back again. What you're doing can't work well for couple of reasons:
vendTextView and returnView don't take indexPath as parameter - your cache is storing something and fetching something, but you have no way of knowing you're storing/fetching it for a correct cell
There's no point in caching the whole text view - why not just cache the text?
Try something like that:
Have your FormCollectionViewCell just have the text view as subview, and modify your code like so:
class YourViewController : UIViewController, UICollectionViewDataSource, UICollectionViewDelegate
{
var texts = [IndexPath : String]()
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "FormCell", for: indexPath)
if let formCell = cell as? FormCollectionViewCell {
cell.textView.text = texts[indexPath]
return cell
}
}
func collectionView(_ collectionView: UICollectionView,
didEndDisplaying cell: UICollectionViewCell,
forItemAt indexPath: IndexPath)
{
if let formCell = cell as? FormCollectionViewCell {
{
texts[indexPath] = formCell.textView.text
}
}
}
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 !
Having UICollectionView as a child of UITableView row. UICollectionView contains images, but whenever I scroll tableview down and up the collection view images got vanished randomly. I am attaching images for my problem reference. Please suggest me how to stop this.
I want my tableview to be like this. And its items should not change on scrolling.
----------------------------------------------------------------------------------------------------------------------------------------------
The collectionview images got vanish on scrolling tableview. It looks like this after scrolling up.
Code Is as follow:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{
let cell:PartOfLookTableViewCell = self.looksListTable.dequeueReusableCell(withIdentifier: "cell") as! PartOfLookTableViewCell
let oneRecord = looksArray[indexPath.row]
cell.myCollectionView.loadInitial(_dataArray: oneRecord.imagesArray, isLooks: 1)
return cell
}
Code for loading data to CollectionView:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: looksReuseIdentifier, for: indexPath) as! CustomCollectionViewCell
let oneRecord = inputArray[indexPath.row]
cell.productImage.sd_setImage(with: URL.init(string: oneRecord.thumb_url)){ (image, error, cacheType, url) in
DispatchQueue.main.async {
cell.productImage.image = image
}
}
}
}
}
#Sourabh Bissa :
UITableView reuses the cell using method CellForRowAtIndexPath whenever your new cell gets visible your this method reuse the data source.
The very important thing here is to maintain the data source:
In your case cell for the row at index path giving the updated value to the collection view method but you are not reloading in main Queue. Try to do it immediately after you get the data source.
Your Cell for the row at index path will look like this :
guard let cell = self.tableview.dequeueReusableCell(withIdentifier: "cell") as! PartOfLookTableViewCell else {
return UITableViewCell()
}
let oneRecord = looksArray[indexPath.row]
cell.configureCell(for record : oneRecord with looks : 1)
return cell
and Now in the cell, you will have collection view outlet, where you will implement a collection view data source method and there you download your images asynchronously.
Cell Class will look like this :
class PartOfLookTableViewCell: UITableViewCell {
#IBOutlet weak var collectionView: UICollectionView!
override func awakeFromNib() {
super.awakeFromNib()
// Initialization code
collectionView.delegate = self
collectionView.dataSource = self
}
override func setSelected(_ selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
// Configure the view for the selected state
}
func configureCell(for record : Record , with looks : Int) {
// Here reload your collection view
// This collection view will be specific to the cell.
collectionView.reloadData()
}
}
extension PartOfLookTableViewCell : UICollectionViewDelegate , UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
//return array
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
// Asyncronously download images
}
}
This is how you can achieve your requirements without using any tags. Please let me know if you have any Queries in it.
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()