UITableView scrollToRowAtIndexPath not working for last 4

Question

I am in a UITableViewController and I have textfields inside cells. When the user clicks on the textfield, I implement the UITextFieldDelegate and in method textFieldDidBeganEditing I determine the index of the cell and scroll to that position. It works perfectly for all cells expect for the last 4-5 cells. What am I doing wrong? Thanks.

Solution 1

scrollToRowAtIndexPath: method scrolls the cell to UITableViewScrollPositionTop or UITableViewScrollPositionMiddle only if the tableView's contentSize is large enough to bring the cell to those positions. If the cell you are trying to scroll to top or middle is the last cell or among the last few cells, it can not be scrolled to middle or top. In these situations you need to calculate the contentOffset manually for those cells.

Edit - Calculating the contentOffset:

In order to calculate the contentOffset use the method as specified by @Schoob. Put the following code in your textFieldDidBeginEditing method.

CGPoint origin = textField.frame.origin;
CGPoint point = [textField.superview convertPoint:origin toView:self.tableView];
float navBarHeight = self.navigationController.navigationBar.frame.size.height;
CGPoint offset = tableView.contentOffset;   
// Adjust the below value as you need
offset.y += (point.y - navBarHeight);
[tableView setContentOffset:o animated:YES];

Solution 2

I found the key to using scrollToRowAtIndexPath was to make sure to call this after the view has been presented. I.e. pushed on to a navigationcontroller or presented modally.

My working code goes like this

Calling code

MyViewController *cont = [[MyViewController alloc] initWithMedication:medication];
cont.sectionToShow = 1;
[self.navigationController pushViewController:cont animated:YES];

[cont release];

Viewcontroller code inside viewWillAppear

NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:self.sectionToShow];
[cont.tableview scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:NO];

If I did it any other way there were always edge cases where it didn't work. I guess we want to scroll late in the presentation cycle.

Comments

[user635064]

Thanks for the answer. I think that's the reason, but can you give an example on how I would calculate the new content offset? Thanks again!

[Joshua J. McKinnon]

Yep, my strategy of calling -scrollToRowAtIndexPath from -viewDidLoad is not gonna work.

[Paul Heller]

The question was about how to scroll the last few rows. Using this technique to get the index path is fine, but the problem still exists

[HamasN]

why use offset.y += (point.y - navBarHeight) rather than offset.y = (point.y - navBarHeight).