UIScrollView scroll to bottom programmatically

Question

How can I make a UIScrollView scroll to the bottom within my code? Or in a more generic way, to any point of a subview?

Answer 1

Using UIScrollView's setContentOffset:animated: function to scroll to the bottom in Swift.

let bottomOffset : CGPoint = CGPointMake(0, scrollView.contentSize.height - scrollView.bounds.size.height + scrollView.contentInset.bottom)
scrollView.setContentOffset(bottomOffset, animated: true)

Answer 2

A good way to ensure the bottom of your content is visible is to use the formula:

contentOffsetY = MIN(0, contentHeight - boundsHeight)

This ensures the bottom edge of your content is always at or above the bottom edge of the view. The MIN(0, ...) is required because UITableView (and probably UIScrollView) ensures contentOffsetY >= 0 when the user tries to scroll by visibly snapping contentOffsetY = 0. This looks pretty weird to the user.

The code to implement this is:

UIScrollView scrollView = ...;
CGSize contentSize = scrollView.contentSize;
CGSize boundsSize = scrollView.bounds.size;
if (contentSize.height > boundsSize.height)
{
    CGPoint contentOffset = scrollView.contentOffset;
    contentOffset.y = contentSize.height - boundsSize.height;
    [scrollView setContentOffset:contentOffset animated:YES];
}

Answer 3

Didn't work for me, when I tried to use it in UITableViewController on self.tableView (iOS 4.1), after adding footerView. It scrolls out of the borders, showing black screen.

Alternative solution:

 CGFloat height = self.tableView.contentSize.height; 

 [self.tableView setTableFooterView: myFooterView];
 [self.tableView reloadData];

 CGFloat delta = self.tableView.contentSize.height - height;
 CGPoint offset = [self.tableView contentOffset];
 offset.y += delta;

 [self.tableView setContentOffset: offset animated: YES];

Answer 4

A swifty implementation:

extension UIScrollView {
   func scrollToBottom(animated: Bool) {
     if self.contentSize.height < self.bounds.size.height { return }
     let bottomOffset = CGPoint(x: 0, y: self.contentSize.height - self.bounds.size.height)
     self.setContentOffset(bottomOffset, animated: animated)
  }
}

You call the extension like this :

yourScrollview.scrollToBottom(animated: true)

Answer 5

A Swift 2.2 solution, taking contentInset into account

let bottomOffset = CGPoint(x: 0, y: scrollView.contentSize.height - scrollView.bounds.size.height + scrollView.contentInset.bottom)
scrollView.setContentOffset(bottomOffset, animated: true)

This should be in an extension

extension UIScrollView {

  func scrollToBottom() {
    let bottomOffset = CGPoint(x: 0, y: contentSize.height - bounds.size.height + contentInset.bottom)
    setContentOffset(bottomOffset, animated: true)
  }
}

Note that you may want to check if bottomOffset.y > 0 before scroll

Answer 6

With an (optional) footerView and contentInset, the solution is:

CGPoint bottomOffset = CGPointMake(0, _tableView.contentSize.height - tableView.frame.size.height + _tableView.contentInset.bottom);
if (bottomOffset.y > 0) [_tableView setContentOffset: bottomOffset animated: YES];