UITableView: Keep selection (single selection) when adding cells at top? - ios

Question

This code will restore a cell selection after refresh the UITableView using reloadData:
NSIndexPath *selectedIndexPath = [self.tableView indexPathForSelectedRow];
[self.tableView reloadData];
[self.tableView selectRowAtIndexPath:selectedIndexPath animated:NO scrollPosition:UITableViewScrollPositionNone];
Of course this solution doesn't works, when I add new cells at the top of my TableView. How i can keep selection, when adding cells at the top?

Answer 1

That really depends of your data source. The most common example for simple cases, if it's an array, then you can "remember" the object every time you select a row (tableView:didSelectRowAtIndexPath:)
myObjecyt = [myArray objectAtIndex:indexPath.row];
, and after [table reloadData];, you select the table index:
NSUInteger index = [myArray indexOfObject:myObject];
if (index != NSNotFound) {
NSINdexPath *selectedIndexPath = [NSIndexPath indexPathForRow:index inSection:0];
[self.tableView selectRowAtIndexPath:selectedIndexPath animated:NO scrollPosition:UITableViewScrollPositionNone];
}
But, as I said, it really depends on lot of factors, this is just an example for the basic setup, where the table is populated with data from myArray, without rearranging and omitting items (and has only one section).

Answer 2

You could simply keep track of the number of cells you are adding at the top and increase the index of the row you are selecting with selectRowAtIndexPath: based on that.
Alternatively, if you have any sort of UI element (UIButton, UILabel etc.) then you can set the tag of that element in didSelectRowAtIndexPath: and then access the cell that has the element with that tag (after reloading) using something like UITableViewCell *selectCell = (UITableViewCell *)[[self.view viewWithTag:100] superview];

Answer 3

As #Frane Poljak said, the user tap on a tableView indicates that the object contained in that row is what interests to the user. You have to keep the object as reference to select the cell that contains it again.
Let's say you have an array of Object, you can do this
enum Value
{
case NotSelected
case Selected(object)
}
private var selectionState : Value = .NotSelected
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
selectionState = Selected(dataSource[indexPath.row])
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
[...]
switch selectionState {
case .Selected(let object as! Object):
if dataSource[indexPath.row] == object { cell.selected = true }
else { cell.selected = false }
default : cell.selected = false
}
}

Answer 4

Try this:
-(void) tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
if([indexPath row] == ((NSIndexPath*)[[tableView indexPathsForVisibleRows] lastObject]).row){
//end of loading
int anyIndex = <any number of cell>
NSIndexPath *anyIndexPath = [[NSIndexPath alloc] indexPathForRow:anyIndex inSection:0];
UITableViewCell *anyCell = [table cellForRowAtIndexPath: firstIndexPath]
anyCell.selectionStyle = UITableViewCellSelectionStyle.Default
}
}
This should work.