如何迅速滚动scrollToRow（at：at：animated :)？

Question

I am creating a chat interface.

User's message is put in a new UITable view cell.

And when update the table view, I use the following code.

extension UITableView {

    func scrollToBottom() {
        let rows = self.numberOfRows(inSection: 0)

        if rows > 0 {
            let indexPath = IndexPath(row: rows - 1, section: 0)
            self.scrollToRow(at: indexPath, at: .bottom, animated: true)
        }
    }
}

Actually this works a little better, but there is something strange.

When I turn off the app and turn it on again, or after exiting the screen and entering again, the following issues arise.

The issue is that when I add a new cell, it goes up to the first cell in the table view and back down to the last cell.

As the number of cells increases, the scrolling becomes too fast and too messy.

I just want to keep updating the last cell that is newly registered.

What should I do?

Answer 1

 func textView(textView: UITextView, shouldChangeTextInRange range: NSRange, replacementText text: String) -> Bool {

        let newText = (textView.text as NSString).stringByReplacingCharactersInRange(range, withString: text)
        let numberOfChars = newText.characters.count // for Swift use count(newText)
        let typedStr : String = textView.text
        var compArr = typedStr.componentsSeparatedByString("\n")
        _ = newText.componentsSeparatedByString("\n")
        self.sendBtn.setTitle("Send", forState: .Normal)

        if numberOfChars > 0 {

            self.sendBtn.enabled = true
        }
        else {

            self.TextViewHeight.constant = TEXTVIEW_OFFSET
            self.sendBtn.enabled = false
        }
        let  char = text.cStringUsingEncoding(NSUTF8StringEncoding)!
        let isBackSpace = strcmp(char, "\\b")

        if text == "\n"
        {
            print("Return_Pressed")
            if  compArr.count == 1 || compArr.count == 2 || compArr.count == 3
            {
                self.TextViewHeight.constant =  self.TextViewHeight.constant + 25
                self.tableViewScrollToBottom(false)
            }
            else
            {

            }
        }
    }



func tableViewScrollToBottom(animated: Bool) {

      dispatch_async(dispatch_get_main_queue()) {

                let numberOfSections = self.ChatTableView.numberOfSections
                let numberOfRows = self.ChatTableView.numberOfRowsInSection(numberOfSections-1)

                if numberOfRows > 0 {

                    let indexPath = NSIndexPath(forRow: numberOfRows-1, inSection: (numberOfSections-1))
                    self.ChatTableView.scrollToRowAtIndexPath(indexPath, atScrollPosition: UITableViewScrollPosition.Bottom, animated: animated)
                }

            }
    }

Answer 2

Try calling your scrollToBottom function in viewWillAppear method. Maybe it just needs to update the number of rows when you return to your TableViewController.