How to keep UITableView contentoffset after calling -reloadData

Question

CGPoint offset = [_table contentOffset];
[_table reloadData];
[_table setContentOffset:offset animated:NO];    //unuseful

//    __block UITableView *tableBlock = _table;
//    [self performBlock:^(id sender) {
//        [tableBlock setContentOffset:offset];
//    } afterDelay:2];

I know don't know of any delegate method which gets called after reloadData. And using afterDelay:2 which is kind of a hack may be too short or too long, so how can I implement it?

See [here](https://stackoverflow.com/a/39648633/5175709). This answer works better than all answers provided here. Even Matt Koala's answer my not work 100% of the time :) — mfaani, Oct 10 '18 at 04:05

score 122 · Answer 1 · answered Jul 09 '15 at 17:14

122

I was having trouble with this because I mess with cell sizing in my cellForRowAtIndexPath method. I noticed that the sizing information was off after doing reloadData, so I realized I needed to force it to layout immediately before setting the content offset back.

CGPoint offset = tableView.contentOffset;
[tableView.messageTable reloadData];
[tableView layoutIfNeeded]; // Force layout so things are updated before resetting the contentOffset.
[tableView setContentOffset:offset];

answered Jul 09 '15 at 17:14

Matt Koala

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I don't understand the accepted answer. I see reloadData definitely shifting my content offset and this helped it. – olivaresF Jul 31 '15 at 03:56
layoutIfNeeded() itself worked for me after reloadData() (Swift 3.0) – Engnyl Sep 29 '16 at 14:13
3

`[tableView layoutIfNeeded];` solved my problem. Thank you! – Andrew Bogaevskyi May 19 '17 at 12:30
6

For those of you using `UITableViewAutomaticDimension` in `tableView: heightForRowAtIndexPath:`, in order to get this to work under iOS 10 I also had to return ``UITableViewAutomaticDimension` in `tableView: estimatedHeightForRowAtIndexPath:` to get it to work. Returning a constant in this method didn't work for me. – Evan R Aug 09 '17 at 21:16
The tableView gets stuck lower on the screen if it is reloaded while scrolling using this solution – vikzilla Feb 02 '18 at 06:07
What if you have 100 rows and are looking at the last row before reloading, then after reloading just 1 row - it doesn't make sense to keep the original offset. – Jonny Aug 08 '18 at 01:48
@Jonny is the user looking at the last row? If so then yes it does make sense to keep his original offset! – mfaani Oct 10 '18 at 03:46
just make sure you don't call this inside an animation block. The result would be awkward :/ – mfaani Nov 14 '18 at 17:56
Did NOT work, It fixes the problem on iOS 12 but it doesn't on iOS13 – Bigair May 23 '20 at 14:14

score 97 · Answer 2 · answered Jan 22 '16 at 05:32

97

Calling reloadData on the tableView does not change the content offset. However, if you are using UITableViewAutomaticDimension which was introduced in iOS 8, you could have an issue.

While using UITableViewAutomaticDimension, one needs to write the delegate method tableView: estimatedHeightForRowAtIndexPath: and return UITableViewAutomaticDimension along with tableView: heightForRowAtIndexPath: which also returns the same.

For me, I had issues in iOS 8 while using this. It was because the method estimatedHeightForRowAtIndexPath: method was returning inaccurate values even though I was using UITableViewAutomaticDimension. It was problem with iOS 8 as there was no issue with iOS 9 devices.

I solved this problem by using a dictionary to store the value of the cell's height and returning it. This is what I did.

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSNumber *key = @(indexPath.row);
    NSNumber *height = @(cell.frame.size.height);

    [self.cellHeightsDictionary setObject:height forKey:key];
}

- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSNumber *key = @(indexPath.row);
    NSNumber *height = [self.cellHeightsDictionary objectForKey:key];

    if (height)
    {
        return height.doubleValue;
    }

    return UITableViewAutomaticDimension;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return UITableViewAutomaticDimension;
}

The check for whether height exists is for the first time page loads.

answered Jan 22 '16 at 05:32

Skywalker

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But I have one improvement! Save the indexPath itself instead of just the row. Since I have multiple sections this was a problem... – blackjacx May 31 '16 at 17:23
@blackjacx Yes. If you have multiple sections, your suggestion would be helpful. Thanks for that – Skywalker Jun 01 '16 at 14:25
4

This answer works. However, if your cells contain items that can change height dynamically, like a UITextView, then you need to change the stored height for the row when the height of the cell changes. I update the height when the textViewDidChange() delegate method is called. Works like a charm. – E.Freitas Oct 14 '16 at 18:40
3

This is the CORRECT ANSWER for people using Auto Layout. In 'viewDidLoad', you need to set a non-zero value for 'self.tableView.estimatedRowHeight', and then call 'self.tableView.rowHeight = UITableViewAutomaticDimension'. Then, you need to override 'tableView(:heightForRowAt:)' to return 'UITableViewAutomaticDimension', and also override tableView(:estimatedHeightForRowAt:) to do the same. What an API, huh? Stellar. – Womble Jul 09 '17 at 23:47
Thanks , this should be set to be the accept answer , set estimatedRowHeight to 0 solved my problem of contentOffset changing when tableView reloadData – ximmyxiao Nov 30 '17 at 02:39
This could be an accepted answer depending on the circumstances. This worked for MY project more than any of the other answers. My pagination table view was jumping all over the place when loading new cells. This solved my problem. – Michael Gaines Mar 16 '18 at 20:27
This answer works for me, while the accepted answer doesn't. – tounaobun Jul 09 '19 at 10:12

score 49 · Answer 3 · edited Dec 08 '20 at 09:07

49

Swift 5 variant of @Skywalker answer:

private var heightDictionary: [IndexPath: CGFloat] = [:]

public func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    heightDictionary[indexPath] = cell.frame.size.height
}

public func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
    let height = heightDictionary[indexPath]
    return height ?? UITableView.automaticDimension
}

Another solution (fetched from MessageKit):

This method should be called instead of reloadData. This can fit for specific cases.

extension UITableView {
    public func reloadDataAndKeepOffset() {
        // stop scrolling
        setContentOffset(contentOffset, animated: false)
            
        // calculate the offset and reloadData
        let beforeContentSize = contentSize
        reloadData()
        layoutIfNeeded()
        let afterContentSize = contentSize
            
        // reset the contentOffset after data is updated
        let newOffset = CGPoint(
            x: contentOffset.x + (afterContentSize.width - beforeContentSize.width),
            y: contentOffset.y + (afterContentSize.height - beforeContentSize.height))
        setContentOffset(newOffset, animated: false)
    }
}

edited Dec 08 '20 at 09:07

Okhan Okbay

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answered Oct 10 '17 at 22:27

Nike Kov

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Thanks, setting the estimated height worked for me. I had only implemented heightForRowAt indexpath. – Jeroen Bakker Nov 02 '17 at 10:23
Thx a lot. This fix the issue for me. I am testing in iOS 11 – code4latte Feb 08 '18 at 19:35
First option is fix my issue. Thanks ( tested in iOS 11 & swift 4.1 ) – Alwin May 05 '18 at 08:22
1

The problem with the first solution is that, if the new cell/item with different height is inserted at the top, the system will use the cached cell height. I haven't tried it, but I think this could be solved by invalidating cached cell height when the cell gets reused (look at `prepareForReuse`). – damirstuhec Aug 27 '18 at 07:21
You saved my day! – daxh Aug 30 '18 at 12:41
second solution is working specially when you are adding items to top of UICollectioinView, thanks – Russell Ghana Jan 02 '19 at 07:49
In the fist solution, you have to use `IndexPath` as dictionary key for tableview with more than one section – Giorgio Jul 02 '20 at 10:01
the second answer is the only thing that worked in my case (collection view), thank you very much bro! :) – StackGU Mar 14 '21 at 22:12
move of the master – Nex Mar 19 '22 at 16:48

score 29 · Answer 4 · answered Mar 28 '18 at 15:51

29

In my case uncheck row height automatic and estimate automatic problem solved

answered Mar 28 '18 at 15:51

saranpol

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Thank you so much ! I wasted too much time on this problem... – Jay Oct 10 '19 at 12:25
Great Answer. But how? – Sudhi 9135 Dec 02 '19 at 08:46
Man, give me your address... I will ship you a bottle of whiskey! – Shalugin Apr 13 '21 at 17:07
You are the best! – joe kirk May 20 '21 at 12:12

Cyril · Answer 5 · 2015-08-27T15:59:16.927

28

By default, reloadData keeps the contentOffset. However, it could be updated if you do have inaccurate estimatedRowHeight values.

edited Aug 27 '15 at 15:59

answered Aug 21 '15 at 08:41

Cyril

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How to set estimatedRowHeight correctly if the height of cell is dynamic for each? – Nike Kov Mar 06 '18 at 09:16
@NikKov, as the name suggest it, it is an estimated value that doesn't need to be the exact actual size of your cell. If you know your cells height are generally going to be between 40 and 60 points, then set 50 as estimatedRowHeight. – Cyril Mar 07 '18 at 09:44
2

@Cyril you said `it is an estimated value that doesn't need to be the exact actual size of your cell`, but also said `if you do have inaccurate estimatedRowHeight values`. So how exactly do we know which is accurate? E.g. my cells usually at 40 and 60 and I set 50. However, sometimes an unsual data pop out cause the cell's height grow up to 120, may be 240 or 300. Then what should the accurate estimatedRowHeight should be? – Eddie May 08 '18 at 08:33
1

Hi @Eddie, you can put a couple of `if` `else` statement in `estimatedRowHeight` since it doesn't take much computing time. Therefore, I would suggest you to return a different estimated row height for the unusual data. 120 to 300 is big range, if you have no efficient way to know an approximate size then you should return `UITableViewAutomaticDimension`. – Cyril May 10 '18 at 13:02

score 13 · Answer 6 · answered Jul 27 '18 at 03:13

13

If you implement estimatedHeightForRowAtIndexPath method and your estimate is not right, you will possible get into this situation.

To solve this, you can return a large height that bigger than every cell height in your tableView, like this:

- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath { 
    return 800.f; // if 800 is bigger than every possible value of your cell height.
}

answered Jul 27 '18 at 03:13

bingxin xue

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Just a note, I had this issue and due to the change in content offset, I was able to see a blank space. The solution here might be working good. But, for me While the reload the cellForRowAtIndexPath for 0,0 is not getting called. I had to fix this by returning CGFloat.leastNonzeroMagnitude to estimatedRowHeight. – Sujananth Mar 16 '20 at 12:33

Bohdan Savych · Answer 7 · 2018-01-03T18:23:38.457

10

If you insert data at the beginning of your dataSource array, you need to change contentOffset like this: Swift 3+

func prepareReloadData() {
    let previousContentHeight = tableView.contentSize.height
    let previousContentOffset = tableView.contentOffset.y
    tableView.reloadData()
    let currentContentOffset = tableView.contentSize.height - previousContentHeight + previousContentOffset
    tableView.contentOffset = CGPoint(x: 0, y: currentContentOffset)
}

edited Jan 03 '18 at 18:23

answered Nov 30 '17 at 11:28

Bohdan Savych

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You need to place `tableView.layoutIfNeeded()` after `tableView.reloadData()`. This will give you the updated `currentContentHeight`. – Alan Scarpa Jan 02 '18 at 18:15

score 9 · Accepted Answer · answered Dec 27 '11 at 02:28

9

I was recently working with reloadData -- reloadData doesn't change the contentOffset or scroll the table view. It actually stays the same if the offset is less than the new amount of data.

answered Dec 27 '11 at 02:28

Roy

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yes, you're right! just another call scrollToRowAtIndexPath:atScrollPosition:animated: before i use reloadData. – avincross Dec 27 '11 at 08:19
5

`reloadData` does not change contentOffset, but offset is changed relatively to visible cells. – Timur Bernikovich Dec 27 '16 at 09:48
1

this didn't work for me, I had to store the contentOffset and set it again right after reload. – Scott Fister Jan 31 '17 at 01:31
37

Why this is the accepted answer. I see no solution here. – vhong May 25 '17 at 08:10
9

UITableViewAutomaticDimension may cause a problem with the offset. This answer also is not answer to question. – iluvatar_GR Dec 02 '17 at 18:05
7

I can't agree with this answer. In my call trace I see that `scrollViewDidScroll` invocation was caused by `tableView.reloadData()`: and offset actually changed. – Alexander Stepanishin Apr 06 '18 at 11:20
OMG he is right! The scroll position is maintained on `UICollectionView`. – Baran Sep 03 '19 at 14:23
it could shrink to maintain changes, but this redisplays only visible cells. so, if they dont changed, it shouldn't scroll – Zaporozhchenko Oleksandr Apr 17 '20 at 01:29

score 2 · Answer 9 · answered Aug 24 '16 at 02:15

2

I had the same issue however none of answers suggested here worked. Here's how i solved it. Subclass UITableView and override layoutSubviews method like this:

override func layoutSubviews() {
    let offset = contentOffset
    super.layoutSubviews()
    contentOffset = offset
}

answered Aug 24 '16 at 02:15

Mikhail Vasilev

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However: this does not seem to work if you are animating between two layouts, unfortunately. – Fattie Sep 26 '19 at 01:53

Andrew Romanov · Answer 10 · 2018-06-06T08:55:48.297

@Skywalker's answer showed best workaround for estimated height of cells problem. But sometimes problem lyes in a different place.
Sometimes the problem lyes in contentInsets of table view. If you make reload data while tableView is not visible on the screen you can face with wrong offset after the table view appears on the screen.
It happens because UIViewController can control insets if his scrollView when the scrollView is appearing to allow lying of scrollView below transparent navigationBar and statusBar.
I've faced with this behaviour in iOS 9.1

score 2 · Answer 11 · answered Oct 29 '19 at 16:01

Matt's answer above made me realize that it has to be an issue with the estimatedRowHeight.

So as several pointed out reloadData should not modify the contentOffset so when you set your rowHeight = UITableView.automaticDimension just to be sure to set a correct estimatedRowHeight.

If the estimatedRowHeight is shorter than then UITableView estimated it will try to fix the height and the scrolling behavior would appear but only if the cell with the height problem is visible. In other words, be sure your estimatedRowHeight is set correctly.

I hope this could help someone else.

score -3 · Answer 12 · edited Sep 22 '17 at 03:14

-3

This is working 100%

change the tableView.reloadData()

into

tableView.reloadRows(at: tableView!.indexPathsForVisibleRows!, with: .none)

edited Sep 22 '17 at 03:14

Stephen Rauch

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answered Sep 22 '17 at 02:49

Randolf Dini-ay

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score -4 · Answer 13 · edited Nov 29 '16 at 14:17

-4

For it works fine

[tView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]
             atScrollPosition:UITableViewScrollPositionTop
                     animated:NO];

edited Nov 29 '16 at 14:17

deceze

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answered Nov 29 '16 at 11:52

John

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Hi Deceze, can you give me why it is marked as down ward – John Nov 30 '16 at 06:00
May be because it is not solution for problem. Id is only solution to move a first cell to the top position. – Andrew Romanov Dec 09 '16 at 04:13
Please read the question before answering. This is not a solution to the problem posed. – Womble Jul 09 '17 at 23:37

How to keep UITableView contentoffset after calling -reloadData

13 Answers13

Swift 5 variant of @Skywalker answer:

Another solution (fetched from MessageKit):

Linked