Question

我在从Firebase获取异步操作中的数据后尝试reloadData()。我很难找到合适的位置来执行reloadData()在不同的位置，它要么刷新tableView的一部分而不刷新另一部分，要么根本不刷新，或者更糟糕的是，刷新会使数据集。

到目前为止，这是我的代码，以及我在该特定位置reloadData()时的结果说明：

func getData() {
    DispatchQueue.main.async {
        self.titleView.setTitle(viewController: self, animate: true, title: "Updating...")
    }

    ref.child("conversations").child(userUID).observeSingleEvent(of: .value) { (snapshot) in
        for snap in snapshot.children {
            let snapDatasnapshot = snap as! DataSnapshot
            let snapValues = snapDatasnapshot.value as! [String: AnyObject]
            let recipientUID = snapDatasnapshot.key

            for (key, value) in snapValues {
                let conversationStartTime = value["conversationStartTime"] as! Double

                if calculateMinutesLeft(conversationStartTime) >= 0 {
                    let messagesDatasnapshot = snapDatasnapshot.childSnapshot(forPath: shoutoutID).childSnapshot(forPath: "messages")
                    let messagesArray = messagesDatasnapshot.value as! [String: AnyObject]
                    self.startTimeDictionary[shoutoutID] = conversation

                    for message in messagesArray {
                        let messageID = message.key
                        self.ref.child("messages").child(messageID).observeSingleEvent(of: .value, with: { (messagesSnapshot) in
                            let dictionary = messagesSnapshot.value as! [String: AnyObject]
                            let timestamp = dictionary["timestamp"] as! Double
                            let readReceipt = dictionary["readReceipt"] as! Bool

                            if let messageText = dictionary["message"] {
                                let message = messageText as! String
                                let m = Message(fromUserUID: self.userUID, message: message, timestamp: timestamp, recipientUserUID: recipientUID, imageUrl: nil, readReceipt: readReceipt)
                                self.messagesDictionary[conversation] = m
                                self.messages = Array(self.messagesDictionary.values)
                            } 
                            //Location 1
                            DispatchQueue.main.async {
                                self.tableView.reloadData()
                                self.titleView.setTitle(viewController: self, animate: false, title: "Chats")
                            }
                        })
                    }
                } else {
                    //Expired Convos
                    self.expiredConversations.append(conversation)

                    //Location 2
                    DispatchQueue.main.async {
                       self.tableView.reloadData()
                       self.titleView.setTitle(viewController: self, animate: false, title: "Chats")
                    }
                }
            }
        }

        if self.messages.isEmpty && self.expiredConversations.isEmpty {
            self.titleView.setTitle(viewController: self, animate: false, title: "Chats")
        }

        //Location 3
        DispatchQueue.main.async {
            self.tableView.reloadData()
            self.titleView.setTitle(viewController: self, animate: false, title: "Chats")
        }
    }
    //Location 4
    DispatchQueue.main.async {
        self.tableView.reloadData()
        self.titleView.setTitle(viewController: self, animate: false, title: "Chats")
    }
}

messages将显示在tableView的第0部分，而expiredConversations将显示在tableView的第1部分。

我当前的实现是在位置1和2.这样做正确地重新加载表的两个部分，但是当刷新多次或者当tableView的大小太大时，往往会混淆数据。否则：

仅限位置1，将仅刷新第0部分
仅限位置2，仅刷新第1部分
在第3和第4位，将刷新所有部分，但空messages和expiredConversations

对reloadData()的最佳位置或理想位置有何建议？或者我的实施完全错了？

编辑：tableViewDelegate和tableViewDatasource

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    switch section {
    case 0:
        if messages.isEmpty {
            return 1
        } else {
            return messages.count
        }
    case 1:
        return expiredConversations.count
    default:
        return 0
    }
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    switch indexPath.section {
    case 0:
        if messages.isEmpty {
            let noConversationsCell = tableView.dequeueReusableCell(withIdentifier: "noConversationsCell", for: indexPath) as! NoActiveConversationsTableViewCell
            noConversationsCell.isUserInteractionEnabled = false
            return noConversationsCell
        } else {
            let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! ChatLogTableViewCell
            let message = messages[indexPath.row]
            let conversation = conversations[indexPath.row]
            //All the data model thing to populate the cells
            return cell
        }

    case 1:
        let expiredConversationsCell = tableView.dequeueReusableCell(withIdentifier: "expiredConversationsCell", for: indexPath) as! ExpiredConversationsTableViewCell
        let conversation = expiredConversations[indexPath.row]
        //All the data model thing to populate the cells

        return expiredConversationsCell
    default:
        return UITableViewCell()
    }

}

Swift Firebase：reloadData（）的适当位置

0 个答案: