UIScrollView disable vertical bounce only at bottom

Question

I\'ve been searching for a way to disable vertical bounce for a UIScrollView but only at bottom. I still need to have the bounce at the top.

Couldn\'t find anything.

Answer 1

Based on 0x7fffffff's answer I've created a class:

VerticalBounceControl.h

#import <UIKit/UIKit.h>

@interface VerticalBounceControl : NSObject

@property (nonatomic, assign) BOOL bounce;

- (id) initWithScrollView:(UIScrollView*)scrollView bounceAtTop:(BOOL)bounceAtTop bounceAtBottom:(BOOL)bounceAtBottom;

@end

VerticalBounceControl.m

#import "VerticalBounceControl.h"

@interface VerticalBounceControl ()
@property (nonatomic, retain) UIScrollView* scrollView;
@property (nonatomic, assign) BOOL bounceAtTop;
@property (nonatomic, assign) BOOL bounceAtBottom;
@end

@implementation VerticalBounceControl

- (id) initWithScrollView:(UIScrollView*)scrollView bounceAtTop:(BOOL)bounceAtTop bounceAtBottom:(BOOL)bounceAtBottom {
    self = [super init];
    if(self) {
        self.bounce = YES;
        self.scrollView = scrollView;
        self.bounceAtTop = bounceAtTop;
        self.bounceAtBottom = bounceAtBottom;
        [self.scrollView addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew context:NULL];
    }
    return self;
}

- (void) dealloc {
    [self.scrollView removeObserver:self forKeyPath:@"contentOffset"];
    self.scrollView = nil;
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if ([keyPath isEqualToString:@"contentOffset"]) {
        if (self.bounce && ((self.scrollView.contentOffset.y<=0 && self.bounceAtTop) || (self.scrollView.contentOffset.y>=self.scrollView.contentSize.height-1 && self.bounceAtBottom))) {
            self.scrollView.bounces = YES;
        } else {
            self.scrollView.bounces = NO;
        }
    }
}

@end

that can be used without the caller being a delegate of UIScrollView like this:

VerticalBounceControl* bounceControl = [[VerticalBounceControl alloc] initWithScrollView:anyScrollView bounceAtTop:YES bounceAtBottom:NO];

This way you can have this bounce behavior for UIScrollViews that you don't want to alter their delegate (like UIWebView's one).

Again, thanks go @0x7fffffff for the solution!

Answer 2

I have been looking a solution to disable bottom bounce only for a scrollview with wider contentSize width than device since I am using paging. None of those work for me but I found a way to do it. I thought I should share this since I wasted two days just to do this. I am using Swift 4 but this applies to objective c if you know how to convert this which should be easy if you have experience with both.

This works in a scrollview with device screen frame as frame.

1. Add variable to be aware for scrollview's current page.
   var currentPage : Int!

2. Set initial value
   currentPage = 0

3. Update currentPage after scrolling
   public func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) { let width = scrollView.frame.size.width let page = (scrollView.contentOffset.x + (0.5 * width)) / width currentPage = Int(page) }

4. Filter bottom scrolling and update contentOffset
   public func scrollViewDidScroll(_ scrollView: UIScrollView) { if CGFloat(currentPage) * screenWidth < scrollView.contentOffset.x || CGFloat(currentPage) * screenWidth < scrollView.contentOffset.y || (((CGFloat(currentPage) * screenWidth - scrollView.contentOffset.x) >= 0) && scrollView.contentOffset.y > 0){ scrollView.contentOffset.y = 0 } }

CGFloat(currentPage) * screenWidth < scrollView.contentOffset.x || CGFloat(currentPage) * screenWidth < scrollView.contentOffset.y will filter bottom left and right scrolling

(((CGFloat(currentPage) * screenWidth - scrollView.contentOffset.x) >= 0) && scrollView.contentOffset.y > 0) will filter bottom mid scrolling

scrollView.contentOffset.y = 0 will stop it from scrolling

Answer 3

To disable vertical bounce at the top in Swift:

func scrollViewDidScroll(scrollView: UIScrollView) {
    if scrollView.contentOffset.y < 0 {
        scrollView.contentOffset.y = 0
    }
}

To disable vertical bounce at the bottom in Swift:

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView.contentOffset.y > scrollView.contentSize.height - scrollView.bounds.height {
        scrollView.contentOffset.y = scrollView.contentSize.height - scrollView.bounds.height
    }
}

Answer 4

Swift 3:

This works to disable vertical bounce only at the bottom:

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView.contentOffset.y > scrollView.contentSize.height - scrollView.bounds.height {
        scrollView.contentOffset.y = scrollView.contentSize.height - scrollView.bounds.height
    }
}

Answer 5

Let's disable the bounces when scroll to the bottom.

scrollView.bounces = scrollView.contentOffset.y < scrollView.contentSize.height - scrollView.frame.height

Answer 6

I added fabsf() to 0x7fffffff♦'s solution to also cater for negative(downward) scroll:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if (fabsf(scrollView.contentOffset.y) >= scrollView.contentSize.height - scrollView.frame.size.height) {
        [scrollView setContentOffset:CGPointMake(scrollView.contentOffset.x, scrollView.contentSize.height - scrollView.frame.size.height)];
    }
}