UITableView Refresh without scrolling - ios

Question

I have a _TableView with items , and I want to set automatic refresh,and I don't want it to scroll on refresh , lets say user scrolled 2 pages down , and the refresh trigered -> so I want to put the refreshed content to the top of the table without interupting user's scrolling
Assume user was on row 18
and now the _dataSource is refreshed so it fetched lets say 4 items , so I want user to stay on the item he was.
What would be the best approach to achieve it ??

Answer 1

For Swift 3+:
You need to save the current offset of the UITableView, then reload and then set the offset back on the UITableView.
I have created this function for this purpose:
func reload(tableView: UITableView) {
let contentOffset = tableView.contentOffset
tableView.reloadData()
tableView.layoutIfNeeded()
tableView.setContentOffset(contentOffset, animated: false)
}
Simply call it with: reload(tableView: self.tableView)

Answer 2

SWIFT 3
let contentOffset = self.tableView.contentOffset
self.tableView.reloadData()
self.tableView.layoutIfNeeded()
self.tableView.setContentOffset(contentOffset, animated: false)
This is error of iOS8 when using UITableViewAutomatic Dimension. We need store the content offset of table, reload table, force layout and set contenOffset back.
CGPoint contentOffset = self.tableView.contentOffset;
[self.tableView reloadData];
[self.tableView layoutIfNeeded];
[self.tableView setContentOffset:contentOffset];

Answer 3

I am showing if only one row is being added. You can extend it to multiple rows.
// dataArray is your data Source object
[dataArray insertObject:name atIndex:0];
CGPoint contentOffset = self.tableView.contentOffset;
contentOffset.y += [self tableView:self.tableView heightForRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]];
[self.tableView reloadData];
[self.tableView setContentOffset:contentOffset];
But for this to work you need to have defined - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath the method. Or else, you can directly give your tableview row height if it is constant.

Answer 4

Just set estimatedRowHeight to maximum possible value.
self.tableView.estimatedRowHeight = 1000
self.tableView.estimatedSectionFooterHeight = 100.0
self.tableView.estimatedSectionHeaderHeight = 500.0
That's it!!
Note:
Please do not use FLT_MAX, DBL_MAX value. May be it will crash your app.

Answer 5

I'm doing it this way:
messages.insertContentsOf(incomingMsgs.reverse(), at: 0)
table.reloadData()
// This is for the first load, first 20 messages, scroll to bottom
if (messages.count <= 20) {
let indexToScroll = NSIndexPath(forRow: saferSelf.messages.count - 1, inSection: 0)
table.scrollToRowAtIndexPath(indexToScroll, atScrollPosition: .Top , animated: false)
}
// This is to reload older messages on top of tableview
else {
let indexToScroll = NSIndexPath(forRow: incomingMsgs.count, inSection: 0)
table.scrollToRowAtIndexPath(indexToScroll, atScrollPosition: .Top , animated: false)
// Remove the refreshControl.height + tableHeader.height from the offset so the content remain where it was before reload
let theRightOffset = CGPointMake(0, table.contentOffset.y - refreshControl.frame.height - table.headeView.frame.height)
table.setContentOffset(theRightOffset, animated: false)
}
...also, since I use dynamic cell height, to avoid some weirdness, the estimation is cached:
var heightAtIndexPath = [NSIndexPath: CGFloat]()
func tableView(tableView: UITableView, estimatedHeightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
return heightAtIndexPath[indexPath] ?? UITableViewAutomaticDimension
}
func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
heightAtIndexPath[indexPath] = cell.frame.height
}

Answer 6

Use Extension
create UITableViewExtensions.swift and add following:
extension UITableView {
func reloadDataWithoutScroll() {
let offset = contentOffset
reloadData()
layoutIfNeeded()
setContentOffset(offset, animated: false)
}
}

Answer 7

In iOS 12.x, using Xcode 10.2.1, an easier option is.
UIView.performWithoutAnimation {
let loc = tableView.contentOffset
tableView.reloadRows(at: [indexPath], with: .none)
tableView.contentOffset = loc
}
This works better than following; it shakes at times when the row is not fully visible.
let contentOffset = self.tableView.contentOffset
self.tableView.reloadData()
self.tableView.layoutIfNeeded()
self.tableView.setContentOffset(contentOffset, animated: false)

Answer 8

Swift 4.2 : Simple Solution
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.estimatedRowHeight = 0
self.tableView.estimatedSectionHeaderHeight = 0
self.tableView.estimatedSectionFooterHeight = 0
}
//And then simply update(insert, reloadSections, delete etc) your tableView or reload
tableView.reloadData()
//or
UIView.performWithoutAnimation {
tableView.beginUpdates()
.....
tableView.endUpdates()
}

Answer 9

This code will prevent unnecessary animation and maintain the scroll view's content offset, it worked fine for me.
let lastScrollOffset = tableView.contentOffset
tableView.beginUpdates()
tableView.reloadData()
tableView.endUpdates()
tableView.layer.removeAllAnimations()
tableView.setContentOffset(lastScrollOffset, animated: false)

Answer 10

When you want to reload you have to
self.tableView.reloadData()
self.tableView.layoutIfNeeded()
and also use this UITableViewDelegate
func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
return 'your maximum cell's height'
}
and your tableView will remain on the previous scroll position without scrolling

Answer 11

try to replace
reloadData with
tableView.reloadRows(at: tableView!.indexPathsForVisibleRows!, with: .none),
but you should be care about no cells, if no cells, this method should cause crash.

Answer 12

i wrote something that works perfect for me:
extension UIScrollView {
func reloadDataAndKeepContentOffsetInPlace(reloadData:(() -> Void)) {
let currentContentHeight = contentSize.height
if currentContentHeight == .zero {
reloadData()
return
}
reloadData()
layoutIfNeeded()
let newContentHeight = self.contentSize.height
DispatchQueue.main.async {
var contentOffset = self.contentOffset
contentOffset.y += newContentHeight - currentContentHeight
self.setContentOffset(contentOffset, animated: false)
}
}
}
use like this:
self.reloadSomeData()
collectionView.reloadDataAndKeepContentOffsetInPlace { [weak self] in
guard let self = self else { return }
self.collectionView.reloadData()
}

Answer 13

Try the following.
tableView.estimatedRowHeight = 0
tableView.estimatedSectionHeaderHeight = 0
tableView.estimatedSectionFooterHeight = 0
Source: https://developer.apple.com/forums/thread/86703