I am using swift. I'm trying to create a collectionView segue to lead to a new viewController.
I have a series of (lets say 8) different images and labels as an array within the collectionView, and the when selected, I want the user to be sent to another view controller (with 8 different possibilities - one for each cell). I have been able to get the app to build, but the behaviour from selecting a cell is wrong.
The first cell that is selected has no response, then the next cell initiates a segue - but to the previously selected one! Each time a different cell is selected, it segues to the previous selected cell. Can anyone help me correct this error?
I have used performSegue and pushViewController separately, following different tutorials on youtube, but each resolves to the same issue.
The various view controllers to segue to have been allocated their own storyboardID in the main.storyboard file. The initial view controller is embedded within a navigation controller, and each new veiwcontroller (to segue to) has been connected to the collection view of the main view controller.
import UIKit
class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
#IBOutlet var CollectionView: UICollectionView!
// created an array for labels
let NamesForSectionTitles = ["Overview","Canopy trees","Mid-story trees","Understory plants","Birds","Mammals","Ferns","Butterflys"]
// created list of images to be loaded in the collectionview
let sectionIconImages: [UIImage] = [
UIImage(named: "IMG_8750_landscape_night")!,
UIImage(named: "IMG_8789_Trees")!,
UIImage(named: "IMG_2185_Tree_Olearia")!,
UIImage(named: "_MG_9528_Herb_Flower")!,
UIImage(named: "IMG_3654-")!,
UIImage(named: "IMG_9892-2")!,
UIImage(named: "IMG_9496_Ferns_crozier")!,
UIImage(named: "IMG_7707_Butterfly")!,
]
override func viewDidLoad() {
super.viewDidLoad()
// load the data sources and delegate
CollectionView.dataSource = self
CollectionView.delegate = self
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return NamesForSectionTitles.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) ->
UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CollectionViewCell
cell.SectionTitle.text = NamesForSectionTitles[indexPath.row]
cell.sectionImages.image = sectionIconImages[indexPath.row]
return cell
}
// tells the collection view that upon selecting a cell, show the next UIView controller, as suggested in storyboard name (main.storyboard property) - tutoral from https://www.youtube.com/watch?v=pwZCksvXGRw&list=PLPUDRZDcNNsMdyfZVw4CJDT1Wu8cYx_6E&index=7&t=0s
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
performSegue(withIdentifier: NamesForSectionTitles[indexPath.row], sender: self)
}
}
The viewer should see an image view with a label, that when selected takes them to a new collection view.
Can't Comment so posting an answer
I think
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) is causing the issue.
Please try changing that line to:
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
Related
I'm trying to show some images and hide others using ".isHidden" in my CollectionView. But when I scroll down or reload the collectionView they either get reordered incorrectly or hidden entirely.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ReadBookCell", for: indexPath) as! ReadBookCell
let item = readBookArray[indexPath.item]
for star in cell.starImgOutletCollection {
if star.tag <= item.starRating {
star.isHidden = false
} else {
star.isHidden = true
}
}
return cell
}
Edit: Here is my prepareForReuse
override func prepareForReuse() {
super.prepareForReuse()
for star in starImgOutletCollection {
star.isHidden = true
}
}
Assuming your "stars" are 5 image views in a stack view like this:
And, assuming your starRating will be between 0 and 5 (Zero being no rating yet)...
In your cell class, create a reference to the stack view - since your question mentions starImgOutletCollection I'm assuming you are using #IBOutlet (that is, not creating your views via code), so:
#IBOutlet var starsStackView: UIStackView!
Then, still in your cell class, add this func:
func updateStars(_ starRating: Int) {
for i in 0..<starsStackView.arrangedSubviews.count {
starsStackView.arrangedSubviews[i].isHidden = i >= starRating
}
}
Now, in cellForRowAt
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ReadBookCell", for: indexPath) as! ReadBookCell
let item = readBookArray[indexPath.item]
cell.updateStars(item.starRating)
// do the other stuff to set labels, images, etc
// in the cell
return cell
}
You no longer need the outlet collection for the "star" image views, and you no longer need to implement prepareForReuse().
Why UICollectionView ReloadItems always calls CellForItemAt twice for each item? And how to prevent duplicate calls? How to prevent spending double resources for reloading of selected cells? ReloadData() calls CellForItemAt only once. But it's a waste of resources either to reload all rows and sections when only 2-3 items needed to be updated.
The code example may anything with UICollectiionView. For example:
import UIKit
class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
#IBOutlet weak var collectionView: UICollectionView!
#IBAction func onTestButton(_ sender: Any) {
print("test button tapped")
collectionView.reloadItems(at: [IndexPath(item: 2, section: 0)])
}
let reuseIdentifier = "my cell"
var items = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10"]
override func viewDidLoad() {
collectionView.delegate = self
collectionView.dataSource = self
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return self.items.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! MyCollectionViewCell
cell.myLabel.text = self.items[indexPath.row]
cell.backgroundColor = UIColor.cyan
print("cell for item at \(indexPath.row)")
return cell
}
}
When tapping "test button", console output will be:
test button tapped
cell for item at 2
cell for item at 2
But I need to reload "item at 2" only once, and I don't want to reload all items using reloadData().
You should not make any assumptions about how often the system will call your collectionView(_:cellForItemAt:) method. Just build and return cells when it asks you to. If it sometimes asks you for the same cell twice, just give it the same cell twice.
Collection views and table views ask your to return cells frequently, as the user scrolls. Your collectionView(_:cellForItemAt:) method (or the equivalent table view method) needs to be fast. It shouldn't do network requests, or even decompress JPEG or compressed PNG images from disk unless you cache the results.
I have the following code. For some strange reason, the cell is not registering properly and the cell is not rendered.
I expect there to be 5 purple cells but instead there is only red background.
class RateController: UICollectionViewController {
var user: User?
let cellId = "cellId"
override func viewDidLoad() {
super.viewDidLoad()
collectionView?.backgroundColor = .red
collectionView?.register(UICollectionViewCell.self, forCellWithReuseIdentifier: cellId)
}
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: cellId, for: indexPath)
cell.backgroundColor = .purple
return cell
}
}
There's nothing wrong with your code. I pasted it right into a fresh project, defined the User class, made the necessary adjustments in the storyboard, and ran it:
So if there's a problem, it's somewhere else — not in that code!
I've been thinking about where else the problem could be; the problem you are describing would happen if you disabled the Flow layout in the storyboard and replaced it with an empty Custom layout, like this:
If you did that, set the Layout back to Flow.
The background is black and the cells are white though none of the cells are showing in the simulator? would any one know why this might be?
import UIKit
import Foundation
class ChatLog: UICollectionViewController, UITextFieldDelegate, UICollectionViewDelegateFlowLayout {
let cellId = "cellId"
override func viewDidLoad() {
super.viewDidLoad()
collectionView?.backgroundColor = UIColor.black
collectionView?.register(UICollectionViewCell.self, forCellWithReuseIdentifier: cellId)
}
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: cellId, for: indexPath)
cell.backgroundColor = UIColor.white
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: view.frame.height, height: 80)
}
}
Update:
Initialising the ChatLog view controller programmatically as follows means that the UICollectionView datasource methods aren't called e.g collectionView(_:cellForItemAt:) isn't called.
let newViewController = ChatLog(collectionViewLayout: UICollectionViewLayout())
Replace with this:
let newViewController = ChatLog(collectionViewLayout: UICollectionViewFlowLayout())
--
As you have declared a UICollectionViewController, you don't actually need to set explicitly in code, the delegate and dataSource properties of your collection view.
Simply make sure that in the Main.storyboard, you have set the class of your UICollectionViewController to ChatLog by clicking on the view controller and then the identity inspector. Also ensure that you have clicked the UICollectionViewCell and set it's Identifier to "cellId".
If this is a multiple view controller project, ensure that it is possible to navigate to ChatLog view controller by making it initial view controller or providing segue/navigation to this view controller from another view controller.
Pictures below outline my solution.
Set the delegate and datasource of the collectionView. The datasource and delegate methods(numberOfItemsInSection, cellForItemAtIndexpath, etc) will be called only if you have set the delegate and datasource. You can set it either in code or in storyboard(if you have used storyboard to design the collectionView)
In the viewDidLoad you can add
collectionView.delegate = self
collectionView.datasource = self
I want to dynamically add collection view inside tableview. I have make following code.
A cell class for collectionview
class NewsFeedCollectionViewCell : UICollectionViewCell{
#IBOutlet weak var imageViewSlider: UIImageView!
}
Than assign collectionview in Tableview cellforrow at indexpath
cell.collectionViewNewsFeed.tag = indexPath.row
cell.collectionViewNewsFeed.reloadData()
Than added following delegates of collectionview
// MARK: - Collection view Delegates / Datasources
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return (mutableArrayNewsFeed[collectionView.tag]["images"] as! NSArray).count
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("NewsFeedCollectionViewCell", forIndexPath: indexPath) as! NewsFeedCollectionViewCell
print("tag : \(collectionView.tag) , Row : \(indexPath.row)")
let img = (mutableArrayNewsFeed[collectionView.tag]["images"] as! NSArray)[indexPath.row] as? String ?? "imgLoginScreenLogo"
cell.imageViewSlider.image = UIImage(named: img)
return cell
}
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
print("Collection View Row : \(indexPath.row)")
}
func collectionView(collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize{
return collectionView.frame.size
}
Its adjusting properly but the indexes gets changes while i scroll the collectionview. For ex, I scroll collectionview upto 3 cell than i go to the tableview 4th index than it also set the index of 4th index of collectionview to 3rd.
Simply want to add collection view with multiple images inside Table view. I have added, but after scrolling the collection view to 3rd image on 1st cell of tableview, i move to 4th cell of Tableview, there also the collectionview gets scrolled automatically upto 4th cell.
Need to get out of this.
There was an issue with the indexpath, I get the solution by keeping the indexpath in an array.
Refer Following link
https://github.com/ashfurrow/Collection-View-in-a-Table-View-Cell