UICollection View is not reloading while Navigating back? - ios

Question

I need to reload the collection view while navigating back to that particular view.
I tried implementing all the following things but its not working
1.calling self.collectionView.reloadData() in viewDidAppear()
2.calling self.collectionView.reloadData() in viewWillAppear()
even i tried calling viewDidLoad() in viewDidAppear but yet it is not working.
And checked the other same type of questions but it is not working...
the only way it works is by performing segue action but I dont think so it is efficent can anyone suggest me any idea??
enter code here class RoomDeviceListVC: UIViewController , UICollectionViewDelegate , UICollectionViewDataSource , UICollectionViewDelegateFlowLayout ,segueAction{
let functions = DataFunctionalities()
#IBOutlet weak var collectionView1: UICollectionView!
#IBOutlet weak var collectionView2: UICollectionView!
var horizontalBarLeadingConstraint : NSLayoutConstraint?
static var isVisible : Bool?
static var CollectionViewSection : Int!
static var reloadFlag : Int!
static var delegates : CollectionViewRotation? = nil
var uiFunctions = UIFunctions()
var selectedIndex = IndexPath(item: 0, section: 0)
var constant : CGFloat?
let headerView = UIView()
override func viewDidLoad() {
super.viewDidLoad()
uiFunctions.setViewBackground(view: self.view)
self.navigationItem.hidesBackButton = true
setupHeader()
setupConstraints()
setupHorizontalBar()
collectionView2.clipsToBounds = true
RoomDeviceListVC.CollectionViewSection = selectedIndex.section
BottomViewRoomCell.delegates = self
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
// self.collectionView2.reloadData()
}
override func viewDidAppear(_ animated: Bool) {
super.viewWillAppear(true)
self.collectionView2.reloadData()
RoomDeviceListVC.isVisible = true
}
override func viewDidDisappear(_ animated: Bool) {
RoomDeviceListVC.isVisible = false
}
func setupHorizontalBar(){
let horizontalBar = UIView()
self.view.addSubview(horizontalBar)
horizontalBar.translatesAutoresizingMaskIntoConstraints = false
horizontalBar.backgroundColor = .white
horizontalBarLeadingConstraint = horizontalBar.leadingAnchor.constraint(equalTo: collectionView2.leadingAnchor)
horizontalBarLeadingConstraint?.isActive = true
horizontalBar.heightAnchor.constraint(equalToConstant: 3).isActive = true
NSLayoutConstraint(item: horizontalBar, attribute: .width, relatedBy: .equal, toItem: collectionView1, attribute: .width, multiplier: 0.5, constant: 1).isActive = true
horizontalBar.bottomAnchor.constraint(equalTo: collectionView2.topAnchor).isActive = true
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 2
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let menuName = ["Rooms" , "DeviceList"]
let color :[UIColor] = [.green , .blue]
if collectionView == collectionView1{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "MenuBarCell", for: indexPath) as! MenuBarCell
cell.menuLabel.text = menuName[indexPath.section]
cell.menuLabel.textColor = UIColor.darkGray
DispatchQueue.main.async {
self.collectionView1.selectItem(at: self.selectedIndex, animated: false, scrollPosition: .centeredHorizontally)
}
return cell
}
else {
if indexPath.section == 0{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "BottomViewRoomCell", for: indexPath) as! BottomViewRoomCell
cell.backgroundColor = .clear
cell.layer.cornerRadius = 9
cell.layer.masksToBounds = true
return cell
}
else{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "BottomViewDeviceCell", for: indexPath) as! BottomViewDeviceCell
cell.backgroundColor = .clear
cell.layer.cornerRadius = 9
cell.layer.masksToBounds = true
return cell
}
}
}
public func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize{
if collectionView == collectionView1{
return CGSize(width: self.view.frame.width / 2, height: collectionView1.frame.height)
}
else{
return CGSize(width: self.view.frame.width, height: collectionView2.frame.height)
}
}

Answer 1

you may use UINavigationControllerDelegate to handle this situation.
add UINavigationControllerDelegate, sign self to the delegate of your collectionView's navigationController, and then put your personal function inside "willShow/didShow" delegate method. your personal function will be called when you pop back to the collectionView.
some method about cell display is not shown
class HomeCollectionViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout, UINavigationControllerDelegate{
private let cellId = "cellId"
override func viewDidLoad() {
super.viewDidLoad()
// sign navigationController's delegate to collectionViewController itself.
navigationController?.delegate = self
}
// push view controller when cell is selected
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let vc = CustomViewController()
navigationController?.pushViewController(vc, animated: true)
}
// call your personal function when this collection view controller shows back
func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
if viewController == self {
print("will show self")
}
}
func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
if viewController == self {
print("did show self")
}
}
}