Expandable list view scrolling in ios - ios

Question

I am using a table view as an expandable list view.I am using section as parent and cells as child.I am getting list view perfectly but the issue is that i want the expanded section view to come into view if the section at end of the screen is clicked. Currently it expands and stay there so one has to scroll it manually.
Thanks.

Answer 1

The easiest way to do that is to call
-[UITableView scrollToRowAtIndexPath:atScrollPosition:animated:]
But be careful. If you call that right after inserting rows for the section, the animation can look pretty bad (cells flying in from weird locations etc.) The easiest solution to that, is to do that after the row insertion animation is completed. Unfortunately, there is no callback for that and the easiest workaround is to use CATransaction callback like so:
// CATransaction is used to be able to have a callback after rows insertion is finished.
// This call opens CATransaction context
[CATransaction begin];
// This call begins tableView updates (not really needed if you only make one insertion call, or one deletion call, but in this example we do both)
[tableView beginUpdates];
// Insert and delete appropriate rows
[tableView insertRowsAtIndexPaths:indexPathsToInsert withRowAnimation:UITableViewRowAnimationAutomatic];
[tableView deleteRowsAtIndexPaths:indexPathsToDelete withRowAnimation:UITableViewRowAnimationAutomatic];
// completionBlock will be called after rows insertion/deletion animation is done
[CATransaction setCompletionBlock: ^{
// This call will scroll tableView to the top of the 'section' ('section' should have value of the folded/unfolded section's index)
[tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:NSNotFound inSection:section] // you can pass NSNotFound to scroll to the top of the section even if that section has 0 rows
atScrollPosition:UITableViewScrollPositionTop
animated:YES];
}];
// End table view updates
[tableView endUpdates];
// Close CATransaction context
[CATransaction commit];
If you do the folding/unfolding without animation, for example using plain -[UITableView reloadData], you can safely call
-[UITableView scrollToRowAtIndexPath:atScrollPosition:animated:]
directly after -[UITableView reloadData]
like so:
[tableView reloadData];
[tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:NSNotFound inSection:section] // 'section' is the index of the section you want to be scrolled to the top of the screen
atScrollPosition:UITableViewScrollPositionTop
animated:YES];