indexToScrollTo不适用于TableViewCell Swift中的最后一个CollectionView(indexToScrollTo doesnt work with last CollectionView in a TableViewCell Swift)

 我在TableView为垂直和水平滚动和可定制的单元格创建了一个CollectionView 。 这工作到目前为止。 
 
 我希望它在第一次打开应用程序时（以及如果我手动刷新页面）在特定的IndexPath中显示来自CollectionView特定单元格。 我得到了正确的IndexPath，它适用于每个TableViewCell （ CollectionView所在的位置），除了最后一个。 
 
 这是我的代码： 
 
import UIKit
import RealmSwift


class HomeVTwoTableViewCellSmall: UITableViewCell{

//belongs to the center Method
var onceOnly = false
var counterIndexPath = 0

//serves as a translator from ChannelName to the ChannelId
var channelOverview: [String:String] = ["Some: Values"]

//Initiaize the CellChannel Container and Live Programm
var cellChannel: Results<Community>!  
var liveProgramm: Results<Live>?

//Initialize the translated ChannelId
var channelId: String = ""
override func prepareForReuse() {
    channelId = ""
}


var channelTitle = "" {
    didSet {
        let realm = try! Realm()
        //Getting the ChannelId from Dictionary
        self.channelId = self.channelOverview[self.channelTitle]!

        //load data from Realm into variables
        self.cellChannel = realm.objects(Community.self).filter("channelId = \(self.channelId) ").sorted(byKeyPath: "startTime")
        self.liveProgramm = realm.objects(Live.self).filter("channelId = \(self.channelId) ")
        self.collectionView.reloadData()
    }
}
@IBOutlet weak var collectionView: UICollectionView!

override func awakeFromNib() {
    super.awakeFromNib()
    collectionView.delegate = self
    collectionView.dataSource = self
}
}

extension HomeVTwoTableViewCellSmall: UICollectionViewDataSource,UICollectionViewDelegate {

//MARK: Datasource Methods
func numberOfSections(in collectionView: UICollectionView) -> Int
{
    return 1
}

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

//gets the IndexPath to use  
func getLiveIndexPath(){
    var counter = 0
    counterIndexPath = 0
    for i in 0 ..< cellChannel.count
         {
        if (cellChannel[i].communityId != liveProgramm?[0].communityId) {
            counter += 1
        }
        else {
            counterIndexPath = counter
            return
        }
    }
}

//TODO: Center collection view on Live programm
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {

    getLiveIndexPath()

    if !onceOnly {
        let indexToScrollTo = IndexPath(item: counterIndexPath, section: 0)
        //Change position of the Live cell by Changing position "at: ..."
        self.collectionView.scrollToItem(at: indexToScrollTo, at: .centeredHorizontally, animated: false)
        onceOnly = true
    }
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
    guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCellSmall", for: indexPath) as? HomeVTwoCollectionViewCellSmall else
    {
        fatalError("Cell has wrong type")
    }
    let realm = try! Realm()

    let selectedCommunityObject = realm.object(ofType: Community.self, forPrimaryKey: cellChannel[indexPath.row].communityId)!

    //removes the old image and Titel
    cell.imageView.image = UIImage(named: "No Image")
    cell.titleLbl.text = nil

    //inserting the channel specific data
    let url : String = (cellChannel[indexPath.row].pictureId)
    let name : String = (cellChannel[indexPath.row].communityName)
    cell.titleLbl.text = name
    cell.imageView.downloadedFrom(link :"")
    return cell
}


func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    selectedCommunity = (cellChannel[indexPath.row].communityId)
    let home = HomeViewController()
    home.showCommunityDetail()
}
}
 
 它看起来像在最后一个CollectionView ，“onceOnly”布尔值已经是true，但我不明白为什么它在开始时运行，而不是在最后一个运行。 它滚动但不在正确的IndexPath 

I have made a CollectionView in a TableView for vertical and horizontal scrolling and customisable cells. This works so far. 
 
I want it to display specific Cells from the CollectionView at specific IndexPath at the first time opening the app (and if I refresh the page manually). I get the right IndexPath and it works with every TableViewCell (where the CollectionView is inside), except the last one.
 
Here is my Code:
 
import UIKit
import RealmSwift


class HomeVTwoTableViewCellSmall: UITableViewCell{

//belongs to the center Method
var onceOnly = false
var counterIndexPath = 0

//serves as a translator from ChannelName to the ChannelId
var channelOverview: [String:String] = ["Some: Values"]

//Initiaize the CellChannel Container and Live Programm
var cellChannel: Results<Community>!  
var liveProgramm: Results<Live>?

//Initialize the translated ChannelId
var channelId: String = ""
override func prepareForReuse() {
    channelId = ""
}


var channelTitle = "" {
    didSet {
        let realm = try! Realm()
        //Getting the ChannelId from Dictionary
        self.channelId = self.channelOverview[self.channelTitle]!

        //load data from Realm into variables
        self.cellChannel = realm.objects(Community.self).filter("channelId = \(self.channelId) ").sorted(byKeyPath: "startTime")
        self.liveProgramm = realm.objects(Live.self).filter("channelId = \(self.channelId) ")
        self.collectionView.reloadData()
    }
}
@IBOutlet weak var collectionView: UICollectionView!

override func awakeFromNib() {
    super.awakeFromNib()
    collectionView.delegate = self
    collectionView.dataSource = self
}
}

extension HomeVTwoTableViewCellSmall: UICollectionViewDataSource,UICollectionViewDelegate {

//MARK: Datasource Methods
func numberOfSections(in collectionView: UICollectionView) -> Int
{
    return 1
}

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

//gets the IndexPath to use  
func getLiveIndexPath(){
    var counter = 0
    counterIndexPath = 0
    for i in 0 ..< cellChannel.count
         {
        if (cellChannel[i].communityId != liveProgramm?[0].communityId) {
            counter += 1
        }
        else {
            counterIndexPath = counter
            return
        }
    }
}

//TODO: Center collection view on Live programm
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {

    getLiveIndexPath()

    if !onceOnly {
        let indexToScrollTo = IndexPath(item: counterIndexPath, section: 0)
        //Change position of the Live cell by Changing position "at: ..."
        self.collectionView.scrollToItem(at: indexToScrollTo, at: .centeredHorizontally, animated: false)
        onceOnly = true
    }
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
    guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCellSmall", for: indexPath) as? HomeVTwoCollectionViewCellSmall else
    {
        fatalError("Cell has wrong type")
    }
    let realm = try! Realm()

    let selectedCommunityObject = realm.object(ofType: Community.self, forPrimaryKey: cellChannel[indexPath.row].communityId)!

    //removes the old image and Titel
    cell.imageView.image = UIImage(named: "No Image")
    cell.titleLbl.text = nil

    //inserting the channel specific data
    let url : String = (cellChannel[indexPath.row].pictureId)
    let name : String = (cellChannel[indexPath.row].communityName)
    cell.titleLbl.text = name
    cell.imageView.downloadedFrom(link :"")
    return cell
}


func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    selectedCommunity = (cellChannel[indexPath.row].communityId)
    let home = HomeViewController()
    home.showCommunityDetail()
}
}
 
It seems like the in the last CollectionView the "onceOnly" boolean is already true but I don`t get why it works at the beginning but not with the last one. It scrolls but not at the right IndexPath

原文：https://stackoverflow.com/questions/45463975