Scroll to bottom causes crash - ios

Question

So I have this snippet of code that is supposed to handle making my content scroll to the bottom upon toggling of the keyboard. However, all it does is crash every time that I try to do it.
Any insight?
Here is my code:
#objc func handleKeyboardNotification(notification: NSNotification){
if let userinfo = notification.userInfo{
let keyboardFrame = (userinfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
self.bottomConstraint?.constant = -(keyboardFrame.height)
let isKeyboardShowing = notification.name == NSNotification.Name.UIKeyboardWillShow
self.bottomConstraint?.constant = isKeyboardShowing ? -(keyboardFrame.height) : 0
UIView.animate(withDuration: 0, delay: 0, options: UIViewAnimationOptions.curveEaseOut, animations: {
self.view.layoutIfNeeded()
}, completion: { (completion) in
if self.comments.count > 0 && isKeyboardShowing {
let indexPath = IndexPath(item: self.comments.count-1, section: 0)
self.collectionView.scrollToItem(at: indexPath, at: .top, animated: true)
}
})
}
}
I am currently using IGLitkit to populate my view controller. The items are controlled and loaded through this view controller.
import UIKit
import IGListKit
import Foundation
protocol CommentsSectionDelegate: class {
func CommentSectionUpdared(sectionController: CommentsSectionController)
}
class CommentsSectionController: ListSectionController,CommentCellDelegate {
weak var delegate: CommentsSectionDelegate? = nil
var comment: CommentGrabbed?
var eventKey: String?
override init() {
super.init()
// supplementaryViewSource = self
//sets the spacing between items in a specfic section controller
inset = UIEdgeInsets(top: 5, left: 0, bottom: 0, right: 0)
}
// MARK: IGListSectionController Overrides
override func numberOfItems() -> Int {
return 1
}
override func sizeForItem(at index: Int) -> CGSize {
let frame = CGRect(x: 0, y: 0, width: collectionContext!.containerSize.width, height: 50)
let dummyCell = CommentCell(frame: frame)
dummyCell.comment = comment
dummyCell.layoutIfNeeded()
let targetSize = CGSize(width: collectionContext!.containerSize.width, height: 55)
let estimatedSize = dummyCell.systemLayoutSizeFitting(targetSize)
let height = max(40+8+8, estimatedSize.height)
return CGSize(width: collectionContext!.containerSize.width, height: height)
}
override var minimumLineSpacing: CGFloat {
get {
return 0.0
}
set {
self.minimumLineSpacing = 0.0
}
}
override func cellForItem(at index: Int) -> UICollectionViewCell {
guard let cell = collectionContext?.dequeueReusableCell(of: CommentCell.self, for: self, at: index) as? CommentCell else {
fatalError()
}
// print(comment)
cell.comment = comment
cell.delegate = self
return cell
}
override func didUpdate(to object: Any) {
comment = object as? CommentGrabbed
}
override func didSelectItem(at index: Int){
}
/*
func supportedElementKinds() -> [String] {
return [UICollectionElementKindSectionHeader]
}
func viewForSupplementaryElement(ofKind elementKind: String, at index: Int) -> UICollectionReusableView {
guard let view = collectionContext?.dequeueReusableSupplementaryView(ofKind: elementKind, for: self, class: CommentHeader.self, at: index) as? CommentHeader else{
fatalError()
}
view.handle = "Comments"
return view
}
*/
// func optionsButtonTapped(cell: CommentCell) {
// print("like")
//
//
// }
func optionsButtonTapped(cell: CommentCell){
print("like")
let comment = self.comment
_ = comment?.uid
// 3
let alertController = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)
// 4
if comment?.uid != User.current.uid {
let flagAction = UIAlertAction(title: "Report as Inappropriate", style: .default) { _ in
ChatService.flag(comment!)
let okAlert = UIAlertController(title: nil, message: "The post has been flagged.", preferredStyle: .alert)
okAlert.addAction(UIAlertAction(title: "Ok", style: .default))
self.viewController?.present(okAlert, animated: true, completion: nil)
}
let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
alertController.addAction(cancelAction)
alertController.addAction(flagAction)
}else{
let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
let deleteAction = UIAlertAction(title: "Delete Comment", style: .default, handler: { _ in
ChatService.deleteComment(comment!, (comment?.eventKey)!)
let okAlert = UIAlertController(title: nil, message: "Comment Has Been Deleted", preferredStyle: .alert)
okAlert.addAction(UIAlertAction(title: "Ok", style: .default))
self.viewController?.present(okAlert, animated: true, completion: nil)
self.onItemDeleted()
})
alertController.addAction(cancelAction)
alertController.addAction(deleteAction)
}
self.viewController?.present(alertController, animated: true, completion: nil)
}
func onItemDeleted() {
delegate?.CommentSectionUpdared(sectionController: self)
}
/*
func sizeForSupplementaryView(ofKind elementKind: String, at index: Int) -> CGSize {
return CGSize(width: collectionContext!.containerSize.width, height: 40)
}
*/
}
Also note the data source
extension NewCommentsViewController: ListAdapterDataSource {
// 1 objects(for:) returns an array of data objects that should show up in the collection view. loader.entries is provided here as it contains the journal entries.
func objects(for listAdapter: ListAdapter) -> [ListDiffable] {
var items:[ListDiffable] = comments
print("comments = \(comments)")
return [addHeader] + items
}
// 2 For each data object, listAdapter(_:sectionControllerFor:) must return a new instance of a section controller. For now you’re returning a plain IGListSectionController to appease the compiler — in a moment, you’ll modify this to return a custom journal section controller.
func listAdapter(_ listAdapter: ListAdapter, sectionControllerFor object: Any) -> ListSectionController {
//the comment section controller will be placed here but we don't have it yet so this will be a placeholder
if let object = object as? ListDiffable, object === addHeader {
return CommentsHeaderSectionController()
}
let sectionController = CommentsSectionController()
sectionController.delegate = self
return sectionController
}
// 3 emptyView(for:) returns a view that should be displayed when the list is empty. NASA is in a bit of a time crunch, so they didn’t budget for this feature.
func emptyView(for listAdapter: ListAdapter) -> UIView? {
let view = UIView()
view.backgroundColor = UIColor.white
return view
}
}
Controller which contains keyboard function that causes crash
import UIKit
import IGListKit
import Firebase
class NewCommentsViewController: UIViewController, UITextFieldDelegate,CommentsSectionDelegate {
//array of comments which will be loaded by a service function
var comments = [CommentGrabbed]()
var messagesRef: DatabaseReference?
var bottomConstraint: NSLayoutConstraint?
public let addHeader = "addHeader" as ListDiffable
public var eventKey = ""
//This creates a lazily-initialized variable for the IGListAdapter. The initializer requires three parameters:
//1 updater is an object conforming to IGListUpdatingDelegate, which handles row and section updates. IGListAdapterUpdater is a default implementation that is suitable for your usage.
//2 viewController is a UIViewController that houses the adapter. This view controller is later used for navigating to other view controllers.
//3 workingRangeSize is the size of the working range, which allows you to prepare content for sections just outside of the visible frame.
lazy var adapter: ListAdapter = {
return ListAdapter(updater: ListAdapterUpdater(), viewController: self)
}()
// 1 IGListKit uses IGListCollectionView, which is a subclass of UICollectionView, which patches some functionality and prevents others.
let collectionView: UICollectionView = {
// 2 This starts with a zero-sized rect since the view isn’t created yet. It uses the UICollectionViewFlowLayout just as the ClassicFeedViewController did.
let view = UICollectionView(frame: CGRect.zero, collectionViewLayout: UICollectionViewFlowLayout())
// 3 The background color is set to white
view.backgroundColor = UIColor.white
return view
}()
//will fetch the comments from the database and append them to an array
fileprivate func fetchComments(){
comments.removeAll()
messagesRef = Database.database().reference().child("Comments").child(eventKey)
print(eventKey)
// print(comments.count)
var query = messagesRef?.queryOrderedByKey()
query?.observe(.value, with: { (snapshot) in
guard var allObjects = snapshot.children.allObjects as? [DataSnapshot] else {
return
}
print(snapshot)
allObjects.forEach({ (snapshot) in
guard let commentDictionary = snapshot.value as? [String: Any] else{
return
}
guard let uid = commentDictionary["uid"] as? String else{
return
}
UserService.show(forUID: uid, completion: { (user) in
if let user = user {
var commentFetched = CommentGrabbed(user: user, dictionary: commentDictionary)
commentFetched.commentID = snapshot.key
let filteredArr = self.comments.filter { (comment) -> Bool in
return comment.commentID == commentFetched.commentID
}
if filteredArr.count == 0 {
self.comments.append(commentFetched)
}
self.adapter.performUpdates(animated: true)
}
self.comments.sort(by: { (comment1, comment2) -> Bool in
return comment1.creationDate.compare(comment2.creationDate) == .orderedAscending
})
self.comments.forEach({ (comments) in
})
})
})
}, withCancel: { (error) in
print("Failed to observe comments")
})
//first lets fetch comments for current event
}
lazy var submitButton : UIButton = {
let submitButton = UIButton(type: .system)
submitButton.setTitle("Submit", for: .normal)
submitButton.setTitleColor(.black, for: .normal)
submitButton.titleLabel?.font = UIFont.boldSystemFont(ofSize: 14)
submitButton.addTarget(self, action: #selector(handleSubmit), for: .touchUpInside)
submitButton.isEnabled = false
return submitButton
}()
//allows you to gain access to the input accessory view that each view controller has for inputting text
lazy var containerView: UIView = {
let containerView = UIView()
containerView.backgroundColor = .white
containerView.addSubview(self.submitButton)
self.submitButton.anchor(top: containerView.topAnchor, left: nil, bottom: containerView.bottomAnchor, right: containerView.rightAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 12, width: 50, height: 0)
containerView.addSubview(self.commentTextField)
self.commentTextField.anchor(top: containerView.topAnchor, left: containerView.leftAnchor, bottom: containerView.bottomAnchor, right: self.submitButton.leftAnchor, paddingTop: 0, paddingLeft: 12, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
self.commentTextField.delegate = self
let lineSeparatorView = UIView()
lineSeparatorView.backgroundColor = UIColor.rgb(red: 230, green: 230, blue: 230)
containerView.addSubview(lineSeparatorView)
lineSeparatorView.anchor(top: containerView.topAnchor, left: containerView.leftAnchor, bottom: nil, right: containerView.rightAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0.5)
return containerView
}()
lazy var commentTextField: UITextField = {
let textField = UITextField()
textField.placeholder = "Add a comment"
textField.delegate = self
textField.addTarget(self, action: #selector(textFieldDidChange(_:)), for: .editingChanged)
return textField
}()
#objc func textFieldDidChange(_ textField: UITextField) {
let isCommentValid = commentTextField.text?.characters.count ?? 0 > 0
if isCommentValid {
submitButton.isEnabled = true
}else{
submitButton.isEnabled = false
}
}
#objc func handleSubmit(){
guard let comment = commentTextField.text, comment.characters.count > 0 else{
return
}
let userText = Comments(content: comment, uid: User.current.uid, profilePic: User.current.profilePic!,eventKey: eventKey)
sendMessage(userText)
// will remove text after entered
self.commentTextField.text = nil
}
#objc func handleKeyboardNotification(notification: NSNotification){
if let userinfo = notification.userInfo {
if let keyboardFrame = (userinfo[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
self.bottomConstraint?.constant = -(keyboardFrame.height)
let isKeyboardShowing = notification.name == NSNotification.Name.UIKeyboardWillShow
self.bottomConstraint?.constant = isKeyboardShowing ? -(keyboardFrame.height) : 0
UIView.animate(withDuration: 0, delay: 0, options: UIViewAnimationOptions.curveEaseOut, animations: {
self.view.layoutIfNeeded()
}, completion: { (completion) in
if self.comments.count > 0 && isKeyboardShowing {
let indexPath = IndexPath(item: self.comments.count-1, section: 0)
self.collectionView.scrollToItem(at: indexPath, at: .top, animated: true)
}
})
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(collectionView)
collectionView.addSubview(containerView)
collectionView.alwaysBounceVertical = true
containerView.anchor(top: nil, left: view.leftAnchor, bottom: nil, right: view.rightAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 40)
//view.addConstraintsWithFormatt("H:|[v0]|", views: containerView)
// view.addConstraintsWithFormatt("V:[v0(48)]", views: containerView)
bottomConstraint = NSLayoutConstraint(item: containerView, attribute: .bottom, relatedBy: .equal, toItem: view, attribute: .bottom, multiplier: 1, constant: 0)
view.addConstraint(bottomConstraint!)
adapter.collectionView = collectionView
adapter.dataSource = self
NotificationCenter.default.addObserver(self, selector: #selector(handleKeyboardNotification), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(handleKeyboardNotification), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
collectionView.register(CommentCell.self, forCellWithReuseIdentifier: "CommentCell")
collectionView.register(CommentHeader.self, forCellWithReuseIdentifier: "HeaderCell")
self.collectionView.contentInset = UIEdgeInsetsMake(20, 0, 0, 0)
fetchComments()
// Do any additional setup after loading the view.
}
//look here
func CommentSectionUpdared(sectionController: CommentsSectionController){
print("like")
self.fetchComments()
self.adapter.performUpdates(animated: true)
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
tabBarController?.tabBar.isHidden = true
submitButton.isUserInteractionEnabled = true
}
//viewDidLayoutSubviews() is overridden, setting the collectionView frame to match the view bounds.
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
collectionView.frame = view.bounds
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
extension NewCommentsViewController: ListAdapterDataSource {
// 1 objects(for:) returns an array of data objects that should show up in the collection view. loader.entries is provided here as it contains the journal entries.
func objects(for listAdapter: ListAdapter) -> [ListDiffable] {
var items:[ListDiffable] = comments
print("comments = \(comments)")
return [addHeader] + items
}
// 2 For each data object, listAdapter(_:sectionControllerFor:) must return a new instance of a section controller. For now you’re returning a plain IGListSectionController to appease the compiler — in a moment, you’ll modify this to return a custom journal section controller.
func listAdapter(_ listAdapter: ListAdapter, sectionControllerFor object: Any) -> ListSectionController {
//the comment section controller will be placed here but we don't have it yet so this will be a placeholder
if let object = object as? ListDiffable, object === addHeader {
return CommentsHeaderSectionController()
}
let sectionController = CommentsSectionController()
sectionController.delegate = self
return sectionController
}
// 3 emptyView(for:) returns a view that should be displayed when the list is empty. NASA is in a bit of a time crunch, so they didn’t budget for this feature.
func emptyView(for listAdapter: ListAdapter) -> UIView? {
let view = UIView()
view.backgroundColor = UIColor.white
return view
}
}
extension NewCommentsViewController {
func sendMessage(_ message: Comments) {
ChatService.sendMessage(message, eventKey: eventKey)
}
}