Get UIScrollView to scroll to the top

Question

How do I make a UIScrollView scroll to the top?

Answer 1

Answer for Swift 2.0/3.0/4.0 and iOS 7+:

let desiredOffset = CGPoint(x: 0, y: -self.scrollView.contentInset.top)
self.scrollView.setContentOffset(desiredOffset, animated: true)

Answer 2

To fully replicate the status bar scrollToTop behavior we not only have to set the contentOffset but also want to make sure the scrollIndicators are displayed. Otherwise the user can quickly get lost.

The only public method to accomplish this is flashScrollIndicators. Unfortunately, calling it once after setting the contentOffset has no effect because it's reset immediately. I found it works when doing the flash each time in scrollViewDidScroll:.

// define arbitrary tag number in a global constants or in the .pch file
#define SCROLLVIEW_IS_SCROLLING_TO_TOP_TAG 19291

- (void)scrollContentToTop {
    [self.scrollView setContentOffset:CGPointMake(self.scrollView.contentOffset.x, -self.scrollView.contentInset.top) animated:YES];

    self.scrollView.tag = SCROLLVIEW_IS_SCROLLING_TO_TOP_TAG;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        self.scrollView.tag = 0;
    });
}

In your UIScrollViewDelegate (or UITable/UICollectionViewDelegate) implement this:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if (scrollView.tag == SCROLLVIEW_IS_SCROLLING_TO_TOP_TAG) {
        [scrollView flashScrollIndicators];
    }
}

The hide delay is a bit shorter compared to the status bar scrollToTop behavior but it still looks nice.

Note that I'm abusing the view tag to communicate the "isScrollingToTop" state because I need this across view controllers. If you're using tags for something else you might want to replace this with an iVar or a property.

Answer 3

Scroll to top for UITableViewController, UICollectionViewController or any UIViewController having UIScrollView

extension UIViewController {

  func scrollToTop(animated: Bool) {
    if let tv = self as? UITableViewController {
        tv.tableView.setContentOffset(CGPoint.zero, animated: animated)
    } else if let cv = self as? UICollectionViewController{
        cv.collectionView?.setContentOffset(CGPoint.zero, animated: animated)
    } else {
        for v in view.subviews {
            if let sv = v as? UIScrollView {
                sv.setContentOffset(CGPoint.zero, animated: animated)
            }
        }
    }
  }
}