Check if a UIScrollView reached the top or bottom

Question

Is there a way to know if a UIScrollView has reached the top or bottom? Possibly in the method:

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView 
                  willDecelerate:(BOOL)decelerate

score 201 · Accepted Answer · edited Oct 09 '11 at 20:07

201

Implement the UIScrollViewDelegate in your class, and then add this:

-(void)scrollViewDidScroll: (UIScrollView*)scrollView
{
    float scrollViewHeight = scrollView.frame.size.height;
    float scrollContentSizeHeight = scrollView.contentSize.height;
    float scrollOffset = scrollView.contentOffset.y;

    if (scrollOffset == 0)
    {
        // then we are at the top
    }
    else if (scrollOffset + scrollViewHeight == scrollContentSizeHeight)
    {
        // then we are at the end
    }
}

Hope this is what you are after! Else have a tinker by adding more conditions to the above code and NSLog the value of scrollOffset.

edited Oct 09 '11 at 20:07

Mundi

79,884
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answered Oct 09 '11 at 20:01

Luke

11,426
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5

If you're in a `navigationController`, you might want to do something more like this: `scrollOffset <= (0 - self.navigationController.navigationBar.frame.size.height - 20)` and `(scrollOffset + scrollHeight) >= scrollContentSizeHeight` – Wayne Jan 09 '14 at 22:02
Problem with that is the bounce...everything gets called twice once reaches top or bottom. Is there a solution to that, besides turning off table or collection view bounce? – denikov Aug 29 '14 at 17:04
@denikov did you find any solution for that? – Priyal Jun 07 '17 at 06:57
scrollOffset may be <0 if scrollview top constraint != 0 – famfamfam Mar 02 '21 at 07:59

Alexander Dvornikov · Answer 2 · 2016-03-24T20:48:13.957

Well, contentInsets are also involved, when you try to determine whether scrollView is at the top or at the bottom. You might also be interested in cases when your scrollView is above the top and below the bottom. Here is the code I use to find top and bottom positions:

Swift:

extension UIScrollView {

    var isAtTop: Bool {
        return contentOffset.y <= verticalOffsetForTop
    }

    var isAtBottom: Bool {
        return contentOffset.y >= verticalOffsetForBottom
    }

    var verticalOffsetForTop: CGFloat {
        let topInset = contentInset.top
        return -topInset
    }

    var verticalOffsetForBottom: CGFloat {
        let scrollViewHeight = bounds.height
        let scrollContentSizeHeight = contentSize.height
        let bottomInset = contentInset.bottom
        let scrollViewBottomOffset = scrollContentSizeHeight + bottomInset - scrollViewHeight
        return scrollViewBottomOffset
    }

}

Objective-C:

@implementation UIScrollView (Additions)

- (BOOL)isAtTop {
    return (self.contentOffset.y <= [self verticalOffsetForTop]);
}

- (BOOL)isAtBottom {
    return (self.contentOffset.y >= [self verticalOffsetForBottom]);
}

- (CGFloat)verticalOffsetForTop {
    CGFloat topInset = self.contentInset.top;
    return -topInset;
}

- (CGFloat)verticalOffsetForBottom {
    CGFloat scrollViewHeight = self.bounds.size.height;
    CGFloat scrollContentSizeHeight = self.contentSize.height;
    CGFloat bottomInset = self.contentInset.bottom;
    CGFloat scrollViewBottomOffset = scrollContentSizeHeight + bottomInset - scrollViewHeight;
    return scrollViewBottomOffset;
}


@end

This the good answer, implementing scrollviewdidscroll is bad for performences — Vassily, Dec 18 '14 at 13:56
Because of the vagaries of floating point math, I was getting a "verticalOffsetForBottom" of 1879.05xxx and my contentOffset.y was 1879 when at the bottom in Swift 3. So I changed `return scrollViewBottomOffset` to `return scrollViewBottomOffset.rounded()` — chadbag, May 18 '17 at 12:25
As of iOS 11 `safeAreaInsets` also factor into it. `scrollView.contentOffset.y + scrollView.bounds.height - scrollView.safeAreaInsets.bottom` — InkGolem, Jul 03 '18 at 23:17
In iOS 11 and above you may need to use `adjustedContentInset` instead of `contentInset`. — nemissm, Feb 16 '22 at 23:57

score 41 · Answer 3 · edited Jul 04 '17 at 10:49

If you want the code in swift:

override func scrollViewDidScroll(scrollView: UIScrollView) {

    if (scrollView.contentOffset.y >= (scrollView.contentSize.height - scrollView.frame.size.height)) {
        //reach bottom
    }

    if (scrollView.contentOffset.y <= 0){
        //reach top
    }

    if (scrollView.contentOffset.y > 0 && scrollView.contentOffset.y < (scrollView.contentSize.height - scrollView.frame.size.height)){
        //not top and not bottom
    }
}

Rudolf Adamkovič · Answer 4 · 2017-02-28T15:22:33.340

Simple and clean extension:

import UIKit

extension UIScrollView {

    var scrolledToTop: Bool {
        let topEdge = 0 - contentInset.top
        return contentOffset.y <= topEdge
    }

    var scrolledToBottom: Bool {
        let bottomEdge = contentSize.height + contentInset.bottom - bounds.height
        return contentOffset.y >= bottomEdge
    }

}

On GitHub:

https://github.com/salutis/swift-scroll-view-edges

score 5 · Answer 5 · answered Apr 14 '14 at 18:57

I figured out exactly how to do it:

CGFloat maxPosition = scrollView.contentInset.top + scrollView.contentSize.height + scrollView.contentInset.bottom - scrollView.bounds.size.height;
CGFloat currentPosition = scrollView.contentOffset.y + self.topLayoutGuide.length;

if (currentPosition == maxPosition) {
  // you're at the bottom!
}

score 0 · Answer 6 · answered Sep 11 '18 at 17:55

0

Do it like this(for Swift 3):

class MyClass: UIScrollViewDelegate {

   func scrollViewDidScroll(_ scrollView: UIScrollView) {

        if (scrollView.contentOffset.y >= (scrollView.contentSize.height - scrollView.frame.size.height)) {
           //scrolled to top, do smth
        }


    }
}

answered Sep 11 '18 at 17:55

Radu Ghitescu

11

Welcome to SO! When posting code in your answer, it is helpful o explain how your code solves the OP's problem :) – Joel Sep 11 '18 at 18:12

Check if a UIScrollView reached the top or bottom

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