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 ??
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)
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];
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.
Just set estimatedRowHeight
to maximum possible value.
self.tableView.estimatedRowHeight = 1000
self.tableView.estimatedSectionFooterHeight = 100.0
self.tableView.estimatedSectionHeaderHeight = 500.0
That's it!!
Please do not use FLT_MAX, DBL_MAX
value. May be it will crash your app.
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
}
Use Extension
create UITableViewExtensions.swift
and add following:
extension UITableView {
func reloadDataWithoutScroll() {
let offset = contentOffset
reloadData()
layoutIfNeeded()
setContentOffset(offset, animated: false)
}
}
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
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)
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()
}
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)
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.
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()
}
Try the following.
tableView.estimatedRowHeight = 0
tableView.estimatedSectionHeaderHeight = 0
tableView.estimatedSectionFooterHeight = 0
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.