Swift 自动尺寸单元格高度不起作用

Question

用于消息 ViewController 的 UITableView 单元格仅在我向上或向下滚动表格 View 时以及有时在发送新消息时才能获得正确的高度尺寸。我见过大多数人用 cell.layoutIfNeeded 解决这个问题，但对我来说，它不起作用。有什么想法吗？

automaticDimension 和 cell.layoutIfNeeded:

func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
    messageTableView.estimatedRowHeight = 120.0
    return UITableView.automaticDimension
}


func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "customMessageCell", for: indexPath) as! CustomMessageCell

    cell.ourMessageBackground.backgroundColor = UIColor(displayP3Red: 59/255.0, green: 89/255.0, blue: 152/255.0, alpha: 1)
    cell.ourMessageBody.textColor = UIColor.white
    cell.avatarImageView.backgroundColor = UIColor(white: 0.95, alpha: 1)
    cell.messageBackground.backgroundColor = UIColor(white: 0.95, alpha: 1)
    cell.layoutIfNeeded()  //<-- Layout if needed
    return cell
}

设置单元的代码:

 func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    guard let cell = cell as? CustomMessageCell else { return }

    //Sets cell to message

    let senderId = messageArray[indexPath.row].fromId

    if senderId == Auth.auth().currentUser?.uid as String? {
        //Messages We Sent
        cell.ourMessageBody.text = messageArray[indexPath.row].messageBody

        cell.avatarImageView.isHidden = true
        cell.messageBackground.isHidden = true
        cell.ourMessageBackground.isHidden = false
    } else {
        //Messages someone else sent
        cell.messageBody.text = messageArray[indexPath.row].messageBody

        cell.avatarImageView.isHidden = false
        cell.messageBackground.isHidden = false
        cell.ourMessageBackground.isHidden = true
        cell.layoutIfNeeded()
        //toId ProfileImage
        if let imageID = toId {
            let imagesStorageRef = Storage.storage().reference().child("profilepic/").child(imageID)
            imagesStorageRef.getData(maxSize: 1*1024*1024, completion: { (data, error) in
                if error != nil{
                    print(error)
                    return
                }

                DispatchQueue.main.async {
                    guard let c = tableView.cellForRow(at: indexPath) else { return }

                    cell.avatarImageView?.image = UIImage(data: data!)
                }

            })

        }
    }


}

从 Firebase 检索消息的代码:

  func retrieveMessages() {
    SwipingView.myAdvertiserVar()
    let testUserOrAd = SwipingView.myAdvertiserVar.advertiser


    if testUserOrAd == true{
        if let testId = self.toId{
            let MessageDB = Database.database().reference().child("Users").child(toId!).child("Messages").child(uid!)

            MessageDB.observe(.childAdded) { (snapshot) in
                let snapshotValue =  snapshot.value as? [String: AnyObject]

                let text = snapshotValue!["MessageBody"] as? String
                let fromId = snapshotValue!["FromId"] as? String
                let time = snapshotValue!["TimeStamp"] as? Int
                let message = Message()
                message.messageBody = text
                message.fromId = fromId
                self.user.timeStamp = time

                self.messageArray.append(message)


                self.messageTableView.reloadData()
                self.messageTableView.scrollToRow(at: IndexPath(row: self.messageArray.count-1, section: 0), at: .bottom, animated: false)
            }

        }

    }
}

约束，后代是针对标签本身的，另一个是背景:

这是当我输入长文本时的结果，它被剪切而不是根据内容调整高度:

当我再次输入完全相同的文本并单击“发送”时，我仅获得最新文本的所需结果:

Answer 1

为什么要两者都放

messageTableView.estimatedRowHeight = 120.0
返回UITableView.automaticDimension

在你的 tableView(_ tableView:,estimatedHeightForRowAt indexPath:) 方法中？这样做没有意义，使用estimatedHeight 来帮助tableView 创建单元格。因此，只需返回 CGFloat 即可完成工作，即

func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
    return 120

}

为您的单元格添加AutomaticDimension。添加此:

func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    return UITableView.automaticDimension
}