How to keep UITableView contentoffset after calling -reloadData

Asked 27/12, 2011 at 1:31 Answered 29/10, 2019 at 16:1

Solved ios uitableview reloaddata contentoffset

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?

Fanfani answered 27/12, 2011 at 1:31 Comment(1)

See here. This answer works better than all answers provided here. Even Matt Koala's answer my not work 100% of the time :) – Hurds 10/10, 2018 at 4:5

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.

Canica answered 27/12, 2011 at 2:28 Comment(8)

yes, you're right! just another call scrollToRowAtIndexPath:atScrollPosition:animated: before i use reloadData. – Fanfani 27/12, 2011 at 8:19

reloadData does not change contentOffset, but offset is changed relatively to visible cells. – Chloe 27/12, 2016 at 9:48

this didn't work for me, I had to store the contentOffset and set it again right after reload. – Twinberry 31/1, 2017 at 1:31

Why this is the accepted answer. I see no solution here. – Pteridology 25/5, 2017 at 8:10

UITableViewAutomaticDimension may cause a problem with the offset. This answer also is not answer to question. – Excretion 2/12, 2017 at 18:5

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. – Macdougall 6/4, 2018 at 11:20

OMG he is right! The scroll position is maintained on UICollectionView. – Scout 3/9, 2019 at 14:23

it could shrink to maintain changes, but this redisplays only visible cells. so, if they dont changed, it shouldn't scroll – Condole 17/4, 2020 at 1:29

123

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];

Falkirk answered 9/7, 2015 at 17:14 Comment(9)

I don't understand the accepted answer. I see reloadData definitely shifting my content offset and this helped it. – Rabbinate 31/7, 2015 at 3:56

layoutIfNeeded() itself worked for me after reloadData() (Swift 3.0) – Coercive 29/9, 2016 at 14:13

[tableView layoutIfNeeded]; solved my problem. Thank you! – Ripple 19/5, 2017 at 12:30

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. – Stephanotis 9/8, 2017 at 21:16

The tableView gets stuck lower on the screen if it is reloaded while scrolling using this solution – Melchizedek 2/2, 2018 at 6:7

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. – Gono 8/8, 2018 at 1:48

@Gono is the user looking at the last row? If so then yes it does make sense to keep his original offset! – Hurds 10/10, 2018 at 3:46

just make sure you don't call this inside an animation block. The result would be awkward :/ – Hurds 14/11, 2018 at 17:56

Did NOT work, It fixes the problem on iOS 12 but it doesn't on iOS13 – Surveying 23/5, 2020 at 14:14

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.

Pairoar answered 22/1, 2016 at 5:32 Comment(7)

But I have one improvement! Save the indexPath itself instead of just the row. Since I have multiple sections this was a problem... – Cymbiform 31/5, 2016 at 17:23

@Cymbiform Yes. If you have multiple sections, your suggestion would be helpful. Thanks for that – Pairoar 1/6, 2016 at 14:25

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. – Alyse 14/10, 2016 at 18:40

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. – Thicken 9/7, 2017 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 – Archdeacon 30/11, 2017 at 2:39

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. – Mclin 16/3, 2018 at 20:27

This answer works for me, while the accepted answer doesn't. – Thigmotaxis 9/7, 2019 at 10:12

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)
    }
}

Domenic answered 10/10, 2017 at 22:27 Comment(9)

Thanks, setting the estimated height worked for me. I had only implemented heightForRowAt indexpath. – Purse 2/11, 2017 at 10:23

Thx a lot. This fix the issue for me. I am testing in iOS 11 – Mcgruder 8/2, 2018 at 19:35

First option is fix my issue. Thanks ( tested in iOS 11 & swift 4.1 ) – Greater 5/5, 2018 at 8:22

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). – Unwitting 27/8, 2018 at 7:21

You saved my day! – Terrilynterrine 30/8, 2018 at 12:41

second solution is working specially when you are adding items to top of UICollectioinView, thanks – Microscopium 2/1, 2019 at 7:49

In the fist solution, you have to use IndexPath as dictionary key for tableview with more than one section – Hexastich 2/7, 2020 at 10:1

the second answer is the only thing that worked in my case (collection view), thank you very much bro! :) – Painkiller 14/3, 2021 at 22:12

move of the master – Blowhard 19/3, 2022 at 16:48

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

Bois answered 28/3, 2018 at 15:51 Comment(4)

Thank you so much ! I wasted too much time on this problem... – Janayjanaya 10/10, 2019 at 12:25

Great Answer. But how? – Wriest 2/12, 2019 at 8:46

Man, give me your address... I will ship you a bottle of whiskey! – Alaster 13/4, 2021 at 17:7

You are the best! – Seasonseasonable 20/5, 2021 at 12:12

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

Ko answered 21/8, 2015 at 8:41 Comment(4)

How to set estimatedRowHeight correctly if the height of cell is dynamic for each? – Domenic 6/3, 2018 at 9:16

@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. – Ko 7/3, 2018 at 9:44

@Ko 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? – Ravens 8/5, 2018 at 8:33

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. – Ko 10/5, 2018 at 13:2

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.
}

Lonee answered 27/7, 2018 at 3:13 Comment(1)

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. – Rostov 16/3, 2020 at 12:33

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)
}

Rectangle answered 30/11, 2017 at 11:28 Comment(1)

You need to place tableView.layoutIfNeeded() after tableView.reloadData(). This will give you the updated currentContentHeight. – Hornbeck 2/1, 2018 at 18:15