I have a UICollectionView (let name aCollection) inside a View controller and i use a UICollectionReusableView to show header at the top of collection view
I also have a another UICollectionView (let name bCollection) in UICollectionReusableView. I need to show here top user list. but when i am trying to connect an outlet from storyboard i am getting an error
I know how to reload data in collection view
self.aCollection.reloadData()
My issue is how to connect bCollection outlet and how to reload bCollection to show user list coming from web services?
To take the outlet of bCollection, you need to create a subclass of UICollectionReusableView.
Example:
UIViewController containing aCollection:
class ViewController: UIViewController, UICollectionViewDataSource
{
#IBOutlet weak var aCollectionView: UICollectionView!
override func viewDidLoad()
{
super.viewDidLoad()
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
return 10
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
return collectionView.dequeueReusableCell(withReuseIdentifier: "aCell", for: indexPath)
}
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView
{
return (collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "reusableView", for: indexPath) as! ReusableView)
}
}
UICollectionReusableView containing bCollection:
class ReusableView: UICollectionReusableView, UICollectionViewDataSource
{
#IBOutlet weak var bCollectionView: UICollectionView!
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
return 10
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
return collectionView.dequeueReusableCell(withReuseIdentifier: "bCell", for: indexPath)
}
}
Interface Screenshot
Edit:
To reload bCollection:
You need a reference to the reusableView that you are using. The way you are using it ReusableView() is not right.
Use it like this:
var reusableView: ReusableView?
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView
{
self.reusableView = (collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "reusableView", for: indexPath) as! ReusableView) //Storing the reference to reusableView
return self.reusableView!
}
Now, to reload bCollection,
self.reusableView?.bCollectionView.reloadData()
Since your UICollectionView (bCollection) is inside the UICollectionReusableView you can connect outlet to UICollectionReusableView's class only. So I believe you may have to create a custom class for UICollectionReusableView and assign it in the storyboard and connect bCollection 's outlet to that custom class
Related
this is screenshot(image) of my viewcontrollerI'm using collectionview and placed label in header, header and label created in storyboard
I want to change label text at runtime.
I know I can do it in viewForSupplementaryElementOfKind of collectionview but I want it in viewdidload method
my code is as below
Controller code
class DeleteViewController: UIViewController,UICollectionViewDelegate,UICollectionViewDataSource {
#IBOutlet weak var collectionView: UICollectionView!
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
cell.backgroundColor = .red
return cell
}
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "headerId", for: indexPath) as! TestCollectionReusableView
headerView.labelText.text = "dummy" // this line shows dummy
return headerView
}
let testCollectionReusableView = TestCollectionReusableView()
override func viewDidLoad() {
super.viewDidLoad()
collectionView.register(TestCollectionReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "headerId")
testCollectionReusableView.labelText.text = "Test"
// above line Xcode 12.4 shows error - **Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value**
}
}
Header Class File
class TestCollectionReusableView: UICollectionReusableView {
#IBOutlet weak var labelText: UILabel!
}
Probably the best place to do this is in your DeleteViewController assuming that this class holds your collection view and is a data source for it.
You can simply add a new property such as headerText: String which may then be user in your data source method. Whenever you change the text you should reload your collection view (or just the headers) for change to take effect.
So for instance
class DeleteViewController: UIViewController, UICollectionViewDataSource {
#IBOutlet private var collectionView: UICollectionView?
private var currentHeaderText: String = "Dummy"
override func viewDidLoad() {
super.viewDidLoad()
changeHeaderText(to: "Some other text")
}
private func changeHeaderText(to text: String) {
currentHeaderText = text
collectionView?.reloadData()
}
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "headerId", for: indexPath) as! TestCollectionReusableView
headerView.labelText.text = currentHeaderText
return headerView
}
}
A more optimized approach may be to detect which index paths need reloading and only reload those index paths. It would even be possible to use methods like collectionView?.visibleSupplementaryViews(ofKind: <#T##String#>) and loop through all visible views that correspond to your class to apply the change. But this is all up to you.
I need to use moveItem(at:to:) delegate method in order to move my collection view cells.
When I implement the data source delegation methods it's working fine, but I need to set my data source as UICollectionViewDiffableDataSource and in this way the moveItem(at:to:) did not call.
Any solution to handle,
This way it's work when using delegations :
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 10
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CustomCell
cell.textLabel.text = "Some value"
return cell
}
override func collectionView(_ collectionView: UICollectionView, canMoveItemAt indexPath: IndexPath) -> Bool {
true
}
override func collectionView(_ collectionView: UICollectionView, moveItemAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
print("OK")
}
set data source in this way is not work
func setupDataSource() {
dataSource = UICollectionViewDiffableDataSource<Section, Person>(collectionView: collectionView, cellProvider: {
(collectionView: UICollectionView, indexPath: IndexPath, person: Person) -> UICollectionViewCell? in
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CustomCell
cell.textLabel.text = "Some text"
return cell
})
}
For custom behavior create a subclass of UICollectionViewDiffableDataSource and override the methods there.
I'm looking for your help for my association between a tableview and a collection view.
I've got a CollectionView with 6 horizontal scrollable cells.
In each cell, I would like to put a table view.
For each tableView, I need to know in which cell I am to put my wanted data.
Actually, I make my code work for displaying tableView inside the cells but I'm blocked for finding in which collection view cell I am.
BTW, my Meal_vc_cell controller is actually Empty, it just has a simple outlet. Nothing else.
Here is my code
class TrainFoodPlanViewController: BaseViewController, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout, UITableViewDataSource, UITableViewDelegate {
let train_meals_list: [String] = ["breakfast", "snack_1", "pre_intra_post", "lunch", "snack_2", "diner"]
#IBOutlet weak var trainCollectionView: UICollectionView!
override func viewDidLoad() {
super.viewDidLoad()
self.title = "Food Plan"
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 1
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
return UITableViewCell()
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return train_meals_list.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collection_cell", for: indexPath) as! Meal_vc_cell
cell.meal_number.text = train_meals_list[indexPath.row]
return cell
}
}
Here is what I'm trying to do
There are a number of ways this can be achieved. My recommendation is to subclass UITableView and add a parentCollectionViewIndexPath property
class MyCustomTableView: UITableView {
var parentCollectionViewIndexPath: IndexPath?
}
I'm assuming Meal_vc_cell has an outlet to the relevant tableView. Change that tableView's type to MyCustomTableView
class Meal_vc_cell: UITableViewCell {
#IBOutlet weak var tableView: MyCustomTableView
}
Note: If you're using storyboard, don't forget to update the tableView's class in storyboard as well
Now, just set parentCollectionViewIndexPath in the collectionView's cellForItemAt method
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collection_cell", for: indexPath) as! Meal_vc_cell
cell.tableView.parentCollectionViewIndexPath = indexPath
return cell
}
In my match app Xcode project I have an error stating:
Use of unresolved identifier 'cell'.
My Code:
import UIKit
class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
}
#IBOutlet weak var collectionView: UICollectionView!
var model = CardModel()
var cardArray:[Card] = []
override func viewDidLoad() {
super.viewDidLoad()
//call the getCards method of the card model
cardArray = model.getCards()
collectionView.delegate = self
collectionView.dataSource = self
}
//mark: -UICollectionView Protocol Methods
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return cardArray.count
}
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
//get a cardCollectionViewcell object
let cell =
collectionView.dequeueReusableCell(withReuseIdentifier: "CardCell", for: indexPath) as! CardCollectionViewCell
//get card that
let card = cardArray[indexPath.row]
cell.setCard(card)
return
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
_ = collectionView.cellForItem(at: indexPath) as!CardCollectionViewCell
//flip the card
cell.flip() <--------- THIS IS THE ERROR
Once the error is fixed I am supposed to be able run a match app example on the fake iPhone. It would allow me to flip the cards on a click.
I think you forgot to set reusable identifier
I hope this will be resolve your issue.
To access that cell method you have to declare variable
let cell = collectionView.cellForItem(at: indexPath) as!CardCollectionViewCell
First of all you are misusing collectionView:willDisplay:forItemAt. Move everything into collectionView:cellForItemAt, replace return with return cell and delete willDisplay:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CardCell", for: indexPath) as! CardCollectionViewCell
//get card that
let card = cardArray[indexPath.row]
cell.setCard(card)
return cell
}
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) { ... }
The error is pretty clear: You never declared cell is the scope of didSelectItemAt. Change
let cell = collectionView.cellForItem(at: indexPath) as! CardCollectionViewCell
Have an issue where:
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
is called when an item is selected, but I cannot change any cell properties from this method.
I created a new project with a stripped down UICollectionViewController to change the background color of a cell when selected. It also doesn't work. Here it is:
import UIKit
private let reuseIdentifier = "Cell"
class CollectionViewController: UICollectionViewController {
override func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 5
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath)
cell.backgroundColor = UIColor.blue
return cell
}
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = self.collectionView(self.collectionView, cellForItemAt: indexPath)
cell.backgroundColor = UIColor.green
}
}
The only thing I did in Storyboard is delete the standard View Controller and replace it with a UICollectionViewController, create a subclass of UICollectionViewController and set the controller in the storyboard as that class.
Also, I can confirm that the cell's index path is returned from this method when called from inside the didSelectItemAt method:
self.collectionView.indexPathsForSelectedItems
You are using the wrong API. Never call the delegate method collectionView(_ cellForItemAt:, use cellForItem(at:
if let cell = collectionView.cellForItem(at: indexPath) {
cell.backgroundColor = UIColor.green
}
But be aware that this change is not persistent. When the user scrolls the color will change back to blue.
You can achieve that as below,
ViewController
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ColoursViewCell", for: indexPath) as! ColoursViewCell
return cell
}
UICollectionViewCell
class ColoursViewCell: UICollectionViewCell {
#IBOutlet var photoImageView: UIImageView?
override var bounds: CGRect {
didSet {
self.layoutIfNeeded()
}
}
override var isSelected: Bool{
didSet{
if self.isSelected{
self.photoImageView?.backgroundColor = UIColor.random
}else{
self.photoImageView?.backgroundColor = UIColor.lightGray
}
}
}
}
you can have sample projects from this link I have in GitHub
https://github.com/hadanischal/RandomColors/tree/develop