Swift 3 - UICollectionview Problems on iOS 11.2

Question

I have two problems with UICollectionView. Following are the scenarios:

Problem 1

I have an app that is created in Xcode 8. It's build on iOS 10.3 simulator and everything was good. But when I tried on my device with iOS 11.2, I have a problem with the UICollectionView. When a new data comes, it should be appears on bottom (that's what I want and have done on iOS 10.3). But iOS 11.2 makes it to scroll to top when the new data comes on bottom.

Problem 2

Then I have migrated from Xcode 8 to Xcode 9.2 because Xcode 8 has no direct support to iOS 11. But now on Xcode 9.2 iOS 11.2 simulator, I can't scroll the collectionview clearly and then it breaks in UIAppDelegate with Thread 1: signal SIGABRT.

As long as I know, this kind of error will appear whenever I have a disconnected outlet. But I'm pretty sure all of my outlets have connected.

import UIKit

class cvViewController: UIViewController, UICollectionViewDataSource, UIImagePickerControllerDelegate, UINavigationControllerDelegate, UICollectionViewDelegate {

@IBOutlet var collectionView: UICollectionView!

override func viewDidLoad() {
    super.viewDidLoad()

    collectionView.delegate = self

    collectionView.register(UINib.init(nibName: "Cell", bundle: nil), forCellWithReuseIdentifier: "Cell")
    if let flowLayout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
        flowLayout.estimatedItemSize = CGSize(width: 1,height: 1)
    }

    loadAPI(Page: 1) //display data

    scrollDownButton.clipsToBounds = true
    scrollDownButton.layer.cornerRadius = 15

    sendButton.addTarget(self, action: #selector(cvViewController.sendMessage), for: .touchDown) //push a new data

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    scheduledTimerWithTimeInterval()
    if move == 0{
        scrollToBottomAnimated(animated: true)
    }

    scrollDownButton.addTarget(self, action: #selector(cvchatViewController.scrollToBottomAnimated), for: .touchDown) //it will display last item on screen

    flowLayout.scrollDirection = .vertical

}

func scrollToBottomAnimated(animated: Bool) {
    guard self.collectionView.numberOfSections > 0 else{
        return
    }

    let items = self.collectionView.numberOfItems(inSection: 0)
    if items == 0 { return }

    let collectionViewContentHeight = self.collectionView.collectionViewLayout.collectionViewContentSize.height
    let isContentTooSmall: Bool = (collectionViewContentHeight < self.collectionView.bounds.size.height)

    if isContentTooSmall {
        self.collectionView.scrollRectToVisible(CGRect(x: 0, y: collectionViewContentHeight - 1, width: 1, height: 1), animated: animated)
        return
    }

    self.collectionView.scrollToItem(at: NSIndexPath(item: items - 1, section: 0) as IndexPath, at: .bottom, animated: animated)
}


public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return chatPages.count
}

public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! Cell

     cell.vNameLabel.text = chatPages[indexPath.row].username
     cell.VCDateLabel.text = chatPages[indexPath.row].timeSent
     cell.vImageSend.image = UIImage(named: "1x1px")

    return cell
}


func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
    return true
}

Can anyone help me to solve this? I am just a beginner on Swift by the way. I appreciate all of your responses. Thanks!

NB: I've simplicize the code because the actual code is really complicated.

Answer 1

I solved my problem 1 with replacing collectionView.reloadData() with collectionView.reloadSections(IndexSet(integer: 0)). I got reference from UITableview Scrolls to Top on Reload

Problem 2 solved by removing collectionView.reloadData()

Thanks.