如何在TableView的底部添加新行-聊天消息 [英] How to add new rows at bottom of tableview - chat messages

问题描述

我使用以下代码在每次用户键入消息并单击发送"时添加新消息.效果很好.但是问题是，新消息将插入到表格视图的顶部.我希望将其插入底部.

I'm using the following code to add new messages every time the user types a message and click 'send'. It works great. But the problem is, new messages are inserted at the top of the table view. I want it to be inserted at the bottom.

    import UIKit

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    @IBOutlet var messagesTable: UITableView!
    @IBOutlet var messageTextBox: UITextField!

    var messageArray = [String]()

    @IBAction func sendMessage(sender: AnyObject) {

        messageArray.append(messageTextBox.text!)
        messagesTable.reloadData()
        messageTextBox.text = ""

    }


    override func viewDidLoad() {
        super.viewDidLoad()
    }


    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return messageArray.count
    }

    func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        return 80
    }

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {


        //self.messagesTable.contentInset = UIEdgeInsetsMake(messagesTable.frame.height,0,0,0)

        let cell = NSBundle.mainBundle().loadNibNamed("AgentMessageText", owner: self, options: nil)?.first as! AgentMessageText
        cell.messageText.text = messageArray[indexPath.row]
        return cell
    }

}

下面的代码将行插入到底部.但是新插入的行在视点下方.那就是我们每次必须滚动才能看到它

The below code insert rows to bottom. But the newly inserted rows are below the view point. That is we have to scroll to see it every time

self.messagesTable.contentInset = UIEdgeInsetsMake(messagesTable.frame.height,0,0,0)

推荐答案

此问题的常见解决方案是翻转表格视图(使单元格停留在底部)，然后翻转单元格以使内容正确定位.

A common solution to this problem is to flip the tableview (so cells stick to the bottom) then flip the cells so the content is oriented properly.

示例:

override func viewDidLoad() {
    super.viewDidLoad()

    //flips the tableview (and all cells) upside down
    messagesTableView.transform = CGAffineTransformMakeScale(1, -1)
}

...

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

   ...

   //flips the cell to appear oriented correctly
   cell.transform = CGAffineTransformMakeScale(1, -1)

对于Swift 4

请注意，对于Swift 4.0，上述转换函数如下所示

Just to be clear, for Swift 4.0 the above transform function is as per below

CGAffineTransform(scaleX: 1, y: -1)

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