所以我有这段代码可以处理，使我的内容在切换键盘时滚动到底部。但是，每次尝试这样做时，它都会崩溃。
有什么见解？
这是我的代码：
@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)
}
})
}
}
我目前正在使用IGLitkit来填充我的视图控制器。通过此视图控制器控制和加载项目。
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)
}
*/
}
另请注意数据源
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
}
}
包含导致崩溃的键盘功能的控制器
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)
}
}