save selected row in UITableView after reloadData

Question

I write custom jabber client in iphone.

I use xmppframework as engine.

And I have UITableViewController with NSMutableArray for repesent contact list.

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Answer 1

This is a solution for the case if you want to do table updates and keep the selection:

    NSIndexPath* pathToSelect = [self.tableView indexPathForSelectedRow];
    if (pathToSelect && newRows) {
        int row = pathToSelect.row;
        for (NSIndexPath* path in newRows) {
            if (path.section == pathToSelect.section && path.row <= pathToSelect.row) {
                row++;
            }
        }
        pathToSelect = [NSIndexPath indexPathForRow:row inSection:pathToSelect.section];
    }

    [self.tableView beginUpdates];
    if (reloadRows) [self.tableView reloadRowsAtIndexPaths:reloadRows withRowAnimation:UITableViewRowAnimationFade];
    if (newSections) [self.tableView insertSections:newSections withRowAnimation:UITableViewRowAnimationFade];
    if (newRows) [self.tableView insertRowsAtIndexPaths:newRows withRowAnimation:UITableViewRowAnimationFade];
    [self.tableView endUpdates];

    if (pathToSelect) {
        [self.tableView selectRowAtIndexPath:pathToSelect animated:NO scrollPosition:UITableViewScrollPositionNone];
    }

Answer 2

A lot of these answers are basically using hacks to re-select the row that was previously highlighted by finding out what the previously selected row was from the table view which seems like a bad way to go about it, because usually when your tableview reloads, there is a change in the data that is populating the tableview.

So rather base you re-selection of the row based on your data

let data = ["some", "array", "of", "data"]
let selected = "of" // this should be populated from didSelectRowAt indexPath:

tableView.reloadData()

if let index = data.firstIndex(of: selected) {
  tableView.selectRow(at: IndexPath(row: index, section: 0), animated: false, scrollPosition: .none) // the "of" row should now be highlighted, regardless if the data changed order
}

Answer 3

Edit:

After testing, it doesn't always work!,

the reason is the index may change !

so the correct way is
make new variable

var currentIndex : IndexPath?

and on didSelectRow

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        currentIndex = indexPath
}

then change the function to

 func reloadTableView() {
        let indexPaths = tableview.indexPathsForSelectedRows
        if let currentIndex = self.currentIndex {
        self.tableview.reloadRows(at: [currentIndex], with: .fade)
        for path in indexPaths ?? [] {
            tableview.selectRow(at: path, animated: false, scrollPosition: .none)
            }}
    }

==========

@marmor Answer worked

this is a Swift version of his code

Swift 4.2.3

func reloadTableView() {
        let indexPaths = tableView.indexPathsForSelectedRows
        tableView.reloadData()
        for path in indexPaths ?? [] {
            tableView.selectRow(at: path, animated: false, scrollPosition: .none)
        }
    }

Answer 4

The workaround is to use reloadSections: instead of reloadData. For some reason reloadData removes the current selection.

Answer 5

my two cents for UICollectionView: (credits to Basil..)

I do run in main thread as I reload from a background task:

final override func safeReloadData(){

            DispatchQueue.main.async { [weak self] in

                guard let self = self else {
                    return
                }

                let indexPaths = self.collectionView.indexPathsForSelectedItems
                self.collectionView.reloadData()
                for path in indexPaths ?? [] {
                    self.collectionView.selectItem(at: path, animated: false, scrollPosition: [])
                }
            }
    } 

Answer 6

Adding a delay didn't work for me (tested on iOS 8.4 and iOS 9). What did work was adding a call to -layoutIfNeeded on the selected cell, after calling -selectRowAtIndexPath:animated:scrollPosition:.

NSIndexPath *selectedIndexPath = [self.tableView indexPathForSelectedRow];
[self.tableView reloadData];
[self.tableView selectRowAtIndexPath:selectedIndexPath animated:NO scrollPosition:UITableViewScrollPositionNone];
[[self.tableView cellForRowAtIndexPath:selectedIndexPath] layoutIfNeeded];