Not able to change view colour in UICollection view - ios

I am trying to change colour of the view inside the uicollectionviewcell. But I am not able to change the colour. When I try to connect to the UIViewController to our view controller it say " cannot connect the repetitive content as an outlet.".
When I change the background of the cell it comes like this
As to make it round I am using view and the giving it layer radius properties.
What I am trying to achieve is:
The values are coming from the model class that I have created and assigned it to UIcolectionviewcell. Model contains only one text field that shows the tags.
When user select any tags the background and text colour will change.I am not to achieve this. It might be easy to do but somehow I am not able to achieve this.

Try to change the background color of your rounded element and not of the entire cell
You can create custom UICollectionViewCell and use it to access different items inside of it, like the textfield with your tag

I've added the sample code to achieve your requirements, Please refer and try implementing based on the following code:
//Your model class
class TagModel{
var tag:String!
var selected:Bool!
init(tag:String, selected:Bool) {
self.tag = tag
self.selected = selected
}
}
//your cell with Xib
class TagCell:UICollectionViewCell{
#IBOutlet weak var tagLabel: UILabel!
override func awakeFromNib() {
super.awakeFromNib()
}
func setTag(_ tagModel:TagModel){
tagLabel.layer.masksToBounds = true
tagLabel.layer.cornerRadius = tagLabel.frame.size.height/2
tagLabel.text = tagModel.tag
if tagModel.selected{
tagLabel.textColor = .white
tagLabel.backgroundColor = .blue
}else{
tagLabel.textColor = .gray
tagLabel.backgroundColor = .lightGray
}
}
}
//Your ViewController which has `UICollectionView`
class TagViewController:UIViewController, UICollectionViewDelegate, UICollectionViewDataSource{
var tagModels:[TagModel]!
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
tagModels[indexPath.item].selected = !tagModels[indexPath.item].selected
collectionView.reloadItems(at: [indexPath])
}
}
Note: Please take this code as sample and make modifications based on your implementations.

Related

Interact with element in UITableView.backgroundView

I have a UITableView which displays some data. If there is no data to display, I show an empty with a button in it. I'm taking advantage of the tableView's backgroundView feature to display my empty state. The problem is that I cannot interact with that button. I assume the tableView disables interaction with the background view. Is there some way to enable it?
You should create strong variable to your background view controller.
class ExampleController: UIViewController {
...
#IBOutlet weak var tableView: UITableView!
private let emptyStateVC = EmptyStateVc(nibName: "EmptyStateVc", bundle: nil)
...
private func setupTableView() {
tableView.backgroundView = emptyStateVC.view
tableView.backgroundView?.isUserInteractionEnabled = true
}
}

Why the CollectionViewCell is malfunctioning when scrolling up and down?

The problem
When scrolling up and down in my (programmatically) created collectionView the cells doesn't seem to dequeued properly. This is resulting in duplication of it contents.
Video
Bug replication
Wished behaviour
I wish that the cells correctly getting dequeued and that the content does not get duplicated.
Code snippet
Code snippets are provided via Pastebin below. I had to add some code to satisfy the markdown editor here on SO...
open class CollectionDataSource<Provider: CollectionDataProviderProtocol, Cell: UICollectionViewCell>: NSObject, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout where Cell: ConfigurableCell, Provider.T == Cell.T {
https://pastebin.com/CzHYxTDD
class ProductCell: UICollectionViewCell, ConfigurableCell {
}
https://pastebin.com/9Nkr3s4B
If anything else is need, please ask in the comments.
Each time you call
func configure(_ item: ProductViewModel, at indexPath: IndexPath) {
setupProductImage(with: item.productImage)
setupStackView()
setupProductLines(with: item.productLines)
}
You create new instance productLineLabel = UILabel() inside setupProductLines() and add it to the stackView
You should change this behavior or rather clear the stack view in prepareForReuse method.
Keep in mind, that addArrangedSubview increases suviews retain count for newly added elements. If you stop your applications execution using Debug View Hierarchy button (fig 1), most likely you will see more labels than you expect in the cell.
fig 1.
The problem
Each time I call:
func configure(_ item: ProductViewModel, at indexPath: IndexPath) {
setupProductImage(with: item.productImage)
setupStackView()
setupProductLines(with: item.productLines)
}
I create a new instance of productLineLabel = UILabel()
Therefore it will be duplicated each time the configure(_ item:) is being called from the cellForRowAtIndexPath.
The solution
I used prepareForReuse recommended by llb to remove the subviews that were kind of class UIStackview (containing UILabels). I wrote the following extension to make this less tedious:
func addSubviews(with subviews: [UIView], in parent: UIView) {
subviews.forEach { parent.addSubview($0) }
}
The implementation
The only thing what was left to do was calling the custom extension function from prepareForReuse like so:
override func prepareForReuse() {
let foundStackView = subviews.filter({$0.isKind(of: UIStackView.self)})[0] as? UIStackView
guard let labels = foundStackView?.arrangedSubviews.filter({$0.isKind(of: UILabel.self)}) else { return }
foundStackView?.removeArrangedSubviews(labels, shouldRemoveFromSuperview: true)
}
Credits go to llb, see comments below! <3 Thanks.

buttons and labels resetting when scrolling through collection view

I have a collection view in which each cell possess the ability to be interacted with by the user. Each cell has a like button and a number of likes label. When the button is pressed, the button should turn cyan, and the label (which holds the number of likes) should increment. This setup currently works. However, when I scroll through the collection view and scroll back, the button reverts to its original color (white) and the label decrements down to its original value. I have heard of an ostensibly helpful method called prepareForReuse(), but perhaps I'm not using it correctly. Here is my code:
Here is the array which holds all the cells
var objects = [LikableObject]()
Here is the class definition for these objects
class LikableObject {
var numOfLikes: Int?
var isLikedByUser: Bool?
init(numOfLikes: Int, isLikedByUser: Bool) {
self.numOfLikes = numOfLikes
self.isLikedByUser = isLikedByUser
}
}
Mind you, there is more functionality present in this object, but they are irrelevant for the purposes of this question. One important thing to be noted is that the data for each cell are grabbed using an API. I'm using Alamofire to make requests to an API that will bring back the information for the numOfLikes and isLikedByUser properties for each cell.
Here is how I load up each cell using the collection view's delegate method:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ObjectCell", for: indexPath) as! ObjectCell
cell.configureCell(
isLikedByUser: objects[indexPath.row].isLikedByUser!,
numOfLikes: objects[indexPath.row].numOfLikes!,
)
return cell
}
The ObjectCell class has these three fields:
var isLikedByUser: Bool?
#IBOutlet weak var numOfLikes: UILabel!
#IBOutlet weak var likeBtn: UIButton!
And that configureCell() method, which belongs to the cell class, is here:
public func configureCell(numOfLikes: Int, isLikedByUser: Bool) {
self.isLikedByUser = isLikedByUser
self.numOfLikes.text = String(numOfLikes)
if isLikedByUser {
self.likeBtn.setFATitleColor(color: UIColor.cyan, forState: .normal)
} else {
self.likeBtn.setFATitleColor(color: UIColor.white, forState: .normal)
}
}
And lastly, the prepareForReuse() method is here:
override func prepareForReuse() {
if isLikedByUser! {
self.likeBtn.setTitleColor(UIColor.cyan, for: .normal)
} else {
self.likeBtn.setTitleColor(UIColor.white, for: .normal)
}
}
This doesn't work. And even if it did, I still don't know a way to keep the numOfLikes label from decrementing, or if it should anyway. I'm speculating that a big part of this problem is that I'm not using the prepareForReuse() method correctly... Any help is appreciated, thank you.
prepareForReuse is not the place to modify the cell, as the name states, you "only" have to prepare it for reuse. if you changed something (for example isHidden property of a view), you just have to change them back to initial state.
What you should do though, you can implement didSet for isLikedByUser inside the cell, and apply your modifications to likeBtn in there. (this is of-course the fast solution)
Long solution: It's an anti-pattern that your cell has a property named isLikedByUser, TableViewCell is a View and in all architectures, Views should be as dumb as they can about business logic. the right way is to apply these modifications in configure-cell method which is implemented in ViewController.
If you feel you'll reuse this cell in different viewControllers a lot, at least defined it by a protocol and talk to your cell through that protocol. This way you'll have a more reusable and maintainable code.
Currently all of this is good , the only missing part is cell reusing , you have to reflect the changes in the number of likes to your model array
class ObjectCell:UICollectionViewCell {
var myObject:LikableObject!
}
In cellForRowAt
cell.myObject = objects[indexPath.row]
Now inside cell custom class you have the object reflect any change to it , sure you can use delegate / callback or any observation technique
The prepareForResuse isn't needed here.
You do need to update the model underlying the tableview. One way to verify this is with mock data that is pre-liked and see if that data displays properly.

Swift animate view in tableviewcell

For an app that I'm developing, I'm using a tableview. My tableview, has of course a tableviewcell. In that tableviewcell I'm adding a view programmatically (so nothing in storyboard). It's a view where I draw some lines and text and that becomes a messagebubble. If the messagebubble is seen by the other user you sent it too , a line of the bubble will go open.
So I have the animation function inside the class of that UIView (sendbubble.swift)
Now, it already checks if it is read or not and it opens the right bubble. But normally it should animate (the line that goes open should rotate) in 0.6 seconds. But it animates instantly. So my question is, how do I animate it with a duration?
I would also prefer to still call it in my custom UIView class (sendbubble.swift) . Maybe I need code in my function to check if the cell is presented on my iphone?
Thanks in advance!
func openMessage() {
UIView.animate(withDuration: 0.6, delay: 0.0, options: [], animations: {
var t = CATransform3DIdentity;
t = CATransform3DMakeRotation(CGFloat(3 * Float.pi / 4), 0, 0, 1)
self.moveableLineLayer.transform = t;
}, completion:{(finished:Bool) in })
}
First you need to grab the cell.
Get the indexPath of that cell where you need to show open bubble.
Get the cell from tableView.cellForRowAt(at:indexPath)
We will now have access to that bubble view now you can animate using the same function func openMessage()
Any question? comment.
You need to implement the UITableViewDelegate method tableView(_:willDisplay:forRowAt:) https://developer.apple.com/reference/uikit/uitableviewdelegate/1614883-tableview
That is triggered when the cell is about to be drawn - not when it is created. You will also need to store a state in your model that says if the animation has occurred, otherwise it will happen every time the cell comes back into view.
EXAMPLE
In the view controller (pseudo code)
class CustomViewController: UITableViewDelegate {
//where ever you define your tableview
var tableView:UITableView
tableView.delegate = self
var dataSource //some array that is defining your cells - each object has a property call hasAnimated
func tableView(_ tableView: UITableView, willDisplay cell: ITableViewCell,
forRowAt indexPath: IndexPath) {
if let cell = cell as? CustomTableViewCell, dataSource[indexPath.row].hasAnimated == false {
dataSource[indexPath.row].hasAnimated = true
cell.openMessage()
}
}
}
class CustomTableViewCell: UITableViewCell {
func openMessage() { //your method
}
}

Adding Activity/Loading Indicator at the Bottom of UCollectionView

I am wondering what is the best approach to add an Activity Indicator to the bottom of the UICollectionView.
I would like to able to show and display this cell, and I am wondering how should I do this.
I have searched SO and I have found people suggesting adding a new cell to the last row. But I would like to have the instance of the activity indicator so that I can turn it on or off.
Any suggestions?
You can add a new cell to the last row of your collection view and create a custom UICollectionViewCell class for that cell where you can enter the logic of your cell e.g.:
import UIKit
class LoadingCollectionViewCell: UICollectionViewCell {
#IBOutlet weak var activityIndicator: UIActivityIndicatorView!
override func awakeFromNib() {
self.activityIndicator.startAnimating()
}
func stopLoading() {
self.activityIndicator.stopAnimating()
}
}
You can then call the function stopLoading() in your ViewController when you want the activity indicator to stop.

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