tableView jumping scrolling after reloadData - ios

Question

My tableView scrolling is jumping when I reload tableView with new data. Here is the code for cellForRowAtIndexPath:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let section = indexPath.section
let index = indexPath.row
let info = data[sections[section]]![index] as ConversationMessage
if info.from == .Me {
var cell: ConversationDialogMeTableCell = tableView.dequeueReusableCellWithIdentifier("meCell", forIndexPath: indexPath) as! ConversationDialogMeTableCell
cell.backgroundColor = UIColor.clearColor()
cell.selectionStyle = .None
cell.messageLabel.text = info.text
return cell
} else if info.from == .Other {
var cell: ConversationDialogOtherTableCell = tableView.dequeueReusableCellWithIdentifier("otherCell", forIndexPath: indexPath) as! ConversationDialogOtherTableCell
cell.backgroundColor = UIColor.clearColor()
cell.selectionStyle = .None
cell.personName.textColor = UIColor(hex: 0x6d6d6d)
cell.messageContainerView.backgroundColor = UIColor(hex: 0x6d6d6d)
cell.messageContainerView.layer.cornerRadius = 5
cell.messageContainerView.clipsToBounds = true
Alamofire.request(.GET, info.personImage).response {
(request, response, data, error) in
let image = UIImage(data: data!, scale: 1)!
cell.personImage.image = image
cell.personImage.contentMode = UIViewContentMode.ScaleAspectFill
cell.personImage.layer.cornerRadius = cell.personImage.frame.height / 2
cell.personImage.clipsToBounds = true
}
cell.personName.text = info.personName
cell.personMessage.text = info.text
return cell
}
return UITableViewCell()
}
For the first load scrolling is smooth, but if I will add new data in my tableView and call reloadData() the scrolling is jumping when new cells are shown.
Here is the code where I insert new data to my model:
func client(client: PubNub!, didReceiveMessage message: PNMessageResult!) {
if message.data.subscribedChannel == self.channel {
if let messageInfo: AnyObject = message.data.message {
let date = (messageInfo["date"] as! String).getDateString()
let messageText = messageInfo["message"] as! String
let from: ConversationMessage.sendFromType = (messageInfo["userID"] as! String) == self.userID ? .Me : .Other
let image = messageInfo["userPhoto"] as! String
let name = messageInfo["userName"] as! String
if data[date] != nil {
data[date]!.append(ConversationMessage(text: messageText, from: from, personImage: image, personName: name, date: messageInfo["date"] as! String))
} else {
data[date] = [ConversationMessage(text: messageText, from: from, personImage: image, personName: name, date: messageInfo["date"] as! String)]
}
for section in self.sections {
self.data[section]! = sorted(self.data[section]!) { Utils.compareDateTime($0.date, with: $1.date, order: .OrderedAscending) }
}
tableView.reloadData()
tableViewScrollToBottom(false)
}
}
}
Maybe it happens because of function to scroll tableView to bottom:
func tableViewScrollToBottom(animated: Bool) {
let delay = 0.1 * Double(NSEC_PER_SEC)
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
dispatch_after(time, dispatch_get_main_queue(), {
let numberOfSections = self.tableView.numberOfSections()
let numberOfRows = self.tableView.numberOfRowsInSection(numberOfSections - 1)
if numberOfRows > 0 {
let indexPath = NSIndexPath(forRow: numberOfRows - 1, inSection: (numberOfSections - 1))
self.tableView.scrollToRowAtIndexPath(indexPath, atScrollPosition: UITableViewScrollPosition.Bottom, animated: animated)
}
})
}
One more thing. Should I cache uploaded images? Maybe this is causing jumping scroll. Can someone help me to solve my issue?

Answer 1

Do not return UITableViewAutomaticDimension from
-(CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath;
There may be two possible solutions -
Either you should return max height for your cell.
OR you may cache the cell.bounds.size.height from
tableView:willDisplayCell:forRowAtIndexPath: and return same value in estimatedHeightForRowAtIndexPath