ios - index ScrollTo 不适用于 TableViewCell Swift 中的最后一个 CollectionView

Question

我在 TableView 中创建了一个 CollectionView，用于垂直和水平滚动以及可自定义单元格。到目前为止这有效。

我希望它在第一次打开应用程序时(如果我手动刷新页面)在特定 IndexPath 处显示来自 CollectionView 的特定单元格。我得到了正确的 IndexPath，它适用于每个 TableViewCell(其中 CollectionView 位于内部)，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()
}
}

似乎在最后一个CollectionView中，“onceOnly” bool 值已经是true，但我不明白为什么它在开始时有效，但在最后一个时不起作用。它滚动但不在正确的 IndexPath

Answer 1

很可能，您遇到了重用 UITableViewCell 的问题。发生的情况是，您最初将 channel A 的一个新单元出队，并且它正在正确设置和显示，包括将 onceOnly 设置为 true。然后，此单元格被 tableview 重用，并出队以用于 channel B。但在这种情况下，onceOnly 和 counterIndexPath 仍设置有该信息对于A。

您已经在实现prepareForReuse。您只需在那里重置其他信息即可获得您需要的信息。

override func prepareForReuse() {
     channelId = ""
     onceOnly = false
     counterIndexPath = 0
}