How to transition a UICollectionViewCell via a button to another ViewController? - ios

Question

Question:
How do I transition a UICollectionViewCell I've assigned a button for a UICollection to another View Controller?
Summary:
I've created a UICollection, and UICollectionCells for each image I have.
I create a CollectionCell object for each image I find.
I'm able to create images and buttons for each object, but once I set the target of the button for the cell, I cannot redirect to another ViewController.
Attempts:
I read some other attempts, but they all required that the function be called from the original view controller.
Starting the view controller from within the current view controller:
let secondViewController:SecondViewController = SecondViewController()
self.presentViewController(secondViewController, animated: true, completion: nil)
}
Calling a function from the view controller:
button.addTarget(self,action:#selector(YourControllerName.buttonClicked(_:)),
forControlEvents:.TouchUpInside)
Current Code:
class CollectionViewCell: UICollectionViewCell {
var text: String!
var image_view: UIImageView!
var button: UIButton!
override func awakeFromNib() {
print("Number:" + card_text)
image_view = UIImageView(frame: contentView.frame)
image_view.contentMode = .scaleAspectFill
mage_view.clipsToBounds = true
contentView.addSubview(image_view)
let x_value = contentView.frame.width - contentView.frame.width
let y_value = (contentView.frame.height)/3
let rectangle = CGRect(x: x_value, y: y_value, width: contentView.frame.width, height: 40)
button = UIButton(frame: rectangle)
button.backgroundColor = UIColor.darkGray
button.setTitle(card_text, for: .normal)
button.layer.cornerRadius = 3
button.clipsToBounds = true
button.addTarget(self,action: #selector(ObjectViewCell.buttonPressed), for: .touchUpInside)
contentView.addSubview(button)
}
func buttonPressed(sender:UIButton!) {
print("Practicing: " + self.card_text)
}
}
class Selector: UIViewController
{
var collectionView: UICollectionView!
let base_image = UIImage(named: "blank")
var images = [UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank"), UIImage(named: "blank")]
#IBOutlet weak var main_view: UIView!
override func viewDidLoad() {
super.viewDidLoad()
print("Loading view in Selector")
setupCollectionView()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func setupCollectionView() {
let layout = UICollectionViewFlowLayout()
// Add spacing around each cell.
layout.minimumLineSpacing = 10
layout.minimumInteritemSpacing = 10
// Set each cell size to the size of the image.
layout.estimatedItemSize = CGSize(width: (base_image?.size.width)!, height: (base_image?.size.height)!)
// Set the collection view to the size of the view frame.
collectionView = UICollectionView(frame: main_view.frame, collectionViewLayout: layout)
// Register all images with the CollectionViewCell object.
collectionView.register(CollectionViewCell.self, forCellWithReuseIdentifier: "cell")
// Set the background color.
collectionView.backgroundColor = UIColor.white
collectionView.delegate = self
collectionView.dataSource = self
// Add the collections view to the main view.
view.addSubview(collectionView)
}
}
extension Selector: UICollectionViewDelegate, UICollectionViewDataSource
{
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return images.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! CollectionViewCell
cell.card_text = String(indexPath.item + 1)
cell.awakeFromNib()
return cell
}
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
let cardCell = cell as! ObjectViewCell
cardCell.image_view.image = images[indexPath.row]
}
Update:
Here is what I ended up doing. I read over everybody's comments and answers, and I resolved to make all necessary changes within the view controller who originates the UICollection cells. Therefore, I moved my logic out of the CollectionViewCell object, and instead perform all logic/subview additions in the initialization of the cells.
Now I just need to figure out how to transition a view controller. Thank you everyone.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
let contentView = cell.contentView
let image_view = UIImageView(image: base_image)
image_view.contentMode = .scaleAspectFill
image_view.clipsToBounds = true
contentView.addSubview(image_view)
let x_value = contentView.frame.width - contentView.frame.width
let y_value = (contentView.frame.height)/3
let rectangle = CGRect(x: x_value, y: y_value, width: contentView.frame.width, height: 40)
let button = UIButton(frame: rectangle)
let text = String(indexPath.item + 1)
button.setTitle(text, for: .normal)
button.accessibilityHint = text
button.addTarget(self, action: #selector(buttonPressed), for: .touchUpInside)
contentView.addSubview(button)
return cell
}
func buttonPressed(sender:UIButton!) {
print("Button pressed")
print(sender.accessibilityHint)
//let navController = UINavigationController(rootViewController: self)
// 2. Present the navigation controller
//self.present(navController, animated: true, completion: nil)
}

Answer 1

The problem is that your button's target is the cell, and so the buttonPressed action function is located in the cell. That's a pretty silly thing to do, because (as you rightly say) you cannot call present without a view controller to send it to.
What I would have done is set the button's target/selector in cellForItemAt:. That way, self is the view controller and we can set the target to self. But you didn't do that!
Thus, you need to get from the cell to the view controller that controls it.
However, there is a way. It's called walking the responder chain. Set a UIResponder variable to the button:
var responder : UIResponder = self
Now loop, calling next on responder to walk one step up the chain:
responder = responder.next
Each time, look to see if this responder is a UIViewController. When it is, stop looping and send it present! Thus:
var responder : UIResponder = self
repeat { responder = responder .next } while !(responder is UIViewController)
let vc = responder as! UIViewController
vc.present( // ...
(Still, even though the problem can be solved in this way, I think it was silly to get yourself into this mess in the first place. Making the view controller the target in the first place would have been a much better idea, in my opinion.)