UIScrollView 以编程方式滚动到底部

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

You can use the UIScrollView's setContentOffset:animated: function to scroll to any part of the content view. Here's some code that would scroll to the bottom, assuming your scrollView is self.scrollView :

Objective-C:

CGPoint bottomOffset = CGPointMake(0, self.scrollView.contentSize.height - self.scrollView.bounds.size.height + self.scrollView.contentInset.bottom);
[self.scrollView setContentOffset:bottomOffset animated:YES];

Swift:

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

Hope that helps!

Answer 2

Swift version of the accepted answer for easy copy pasting:

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

Answer 3

最简单的解决方案：

[scrollview scrollRectToVisible:CGRectMake(scrollview.contentSize.width - 1,scrollview.contentSize.height - 1, 1, 1) 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)
  }
}

use it:

yourScrollview.scrollToBottom(animated: true)

Answer 5

Just an enhancement to the existing answer.

CGPoint bottomOffset = CGPointMake(0, self.scrollView.contentSize.height - self.scrollView.bounds.size.height + self.scrollView.contentInset.bottom);
[self.scrollView setContentOffset:bottomOffset animated:YES];

It takes care of the bottom inset as well (in case you're using that to adjust your scroll view when the keyboard is visible)

Answer 6

Setting the content offset to the height of the content size is wrong: it scrolls the bottom of the content to the top of the scroll view, and thus out of sight.

The correct solution is to scroll the bottom of the content to the bottom of the scroll view, like this ( sv is the UIScrollView):

CGSize csz = sv.contentSize;
CGSize bsz = sv.bounds.size;
if (sv.contentOffset.y + bsz.height > csz.height) {
    [sv setContentOffset:CGPointMake(sv.contentOffset.x, 
                                     csz.height - bsz.height) 
                animated:YES];
}

Answer 7

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 8

What if contentSize is lower than bounds ?

For Swift it is:

scrollView.setContentOffset(CGPointMake(0, max(scrollView.contentSize.height - scrollView.bounds.size.height, 0) ), animated: true)

Answer 9

Scroll To Top

- CGPoint topOffset = CGPointMake(0, 0);
- [scrollView setContentOffset:topOffset animated:YES];

Scroll To Bottom

- CGPoint bottomOffset = CGPointMake(0, scrollView.contentSize.height - self.scrollView.bounds.size.height);
 - [scrollView setContentOffset:bottomOffset animated:YES];

Answer 10

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 11

It looks like all of the answers here didn't take the safe area into consideration. Since iOS 11, iPhone X had a safe area introduced. This may affect the scrollView's contentInset .

For iOS 11 and above, to properly scroll to the bottom with the content inset included. You should use adjustedContentInset instead of contentInset . Check this code:

• Swift:

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

• Objective-C

CGPoint bottomOffset = CGPointMake(0, self.scrollView.contentSize.height - self.scrollView.bounds.size.height + self.scrollView.adjustedContentInset.bottom);
[self.scrollView setContentOffset:bottomOffset animated:YES];

• Swift extension (this keeps the original contentOffset.x ):

extension UIScrollView {
    func scrollsToBottom(animated: Bool) {
        let bottomOffset = CGPoint(x: contentOffset.x,
                                   y: contentSize.height - bounds.height + adjustedContentInset.bottom)
        setContentOffset(bottomOffset, animated: animated)
    }
}

References:

• adjustedContentInset

Answer 12

在您使用 UITableview（它是 UIScrollView 的子类）的情况下，我还发现了另一种有用的方法：

[(UITableView *)self.view scrollToRowAtIndexPath:scrollIndexPath atScrollPosition:UITableViewScrollPositionBottom animated:YES];

Answer 13

Swift:

You could use an extension like this:

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

Use:

scrollView.scrollsToBottom(animated: true)

Answer 14

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];

Answer 15

If you somehow change scrollView contentSize (ex. add something to stackView which is inside scrollView) you must call scrollView.layoutIfNeeded() before scrolling, otherwise it does nothing.

Example:

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

Answer 16

valdyr, hope this will help you:

CGPoint bottomOffset = CGPointMake(0, [textView contentSize].height - textView.frame.size.height);

if (bottomOffset.y > 0)
 [textView setContentOffset: bottomOffset animated: YES];

Answer 17

For Horizontal ScrollView

If you like me has a Horizontal ScrollView and want to scroll to end of it (in my case to most right of it), you need to change some parts of the accepted answer:

Objective-C

CGPoint rightOffset = CGPointMake(self.scrollView.contentSize.width - self.scrollView.bounds.size.width + self.scrollView.contentInset.right, 0 );
[self.scrollView setContentOffset:rightOffset animated:YES];

Swift

let rightOffset: CGPoint = CGPoint(x: self.scrollView.contentSize.width - self.scrollView.bounds.size.width + self.scrollView.contentInset.right, y: 0)
self.scrollView.setContentOffset(rightOffset, animated: true)

Answer 18

Category to the rescue!

Add this to a shared utility header somewhere:

@interface UIScrollView (ScrollToBottom)
- (void)scrollToBottomAnimated:(BOOL)animated;
@end

And then to that utility implementation:

@implementation UIScrollView(ScrollToBottom)
- (void)scrollToBottomAnimated:(BOOL)animated
{
     CGPoint bottomOffset = CGPointMake(0, self.contentSize.height - self.bounds.size.height);
     [self setContentOffset:bottomOffset animated:animated];
}
@end

Then Implement it wherever you like, for instance:

[[myWebView scrollView] scrollToBottomAnimated:YES];

Answer 19

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 20

如果你不需要动画，这有效：

[self.scrollView setContentOffset:CGPointMake(0, CGFLOAT_MAX) animated:NO];

Answer 21

While Matt solution seems correct to me you need to take in account also the collection view inset if there is one that has been set-up.

The adapted code will be:

CGSize csz = sv.contentSize;
CGSize bsz = sv.bounds.size;
NSInteger bottomInset = sv.contentInset.bottom;
if (sv.contentOffset.y + bsz.height + bottomInset > csz.height) {
    [sv setContentOffset:CGPointMake(sv.contentOffset.x, 
                                     csz.height - bsz.height + bottomInset) 
                animated:YES];
}

Answer 22

In swift:

   if self.mainScroll.contentSize.height > self.mainScroll.bounds.size.height {
        let bottomOffset = CGPointMake(0, self.mainScroll.contentSize.height - self.mainScroll.bounds.size.height);
        self.mainScroll.setContentOffset(bottomOffset, animated: true)
    }

Answer 23

Solution to scroll to last item of a table View :

Swift 3 :

if self.items.count > 0 {
        self.tableView.scrollToRow(at:  IndexPath.init(row: self.items.count - 1, section: 0), at: UITableViewScrollPosition.bottom, animated: true)
}

Answer 24

CGFloat yOffset = scrollView.contentOffset.y;

CGFloat height = scrollView.frame.size.height;

CGFloat contentHeight = scrollView.contentSize.height;

CGFloat distance = (contentHeight  - height) - yOffset;

if(distance < 0)
{
    return ;
}

CGPoint offset = scrollView.contentOffset;

offset.y += distance;

[scrollView setContentOffset:offset animated:YES];

Answer 25

I found that contentSize doesn't really reflect the actual size of the text, so when trying to scroll to the bottom, it will be a little bit off. The best way to determine the actual content size is actually to use the NSLayoutManager 's usedRectForTextContainer: method:

UITextView *textView;
CGSize textSize = [textView.layoutManager usedRectForTextContainer:textView.textContainer].size;

To determine how much text actually is shown in the UITextView , you can calculate it by subtracting the text container insets from the frame height.

UITextView *textView;
UIEdgeInsets textInsets = textView.textContainerInset;
CGFloat textViewHeight = textView.frame.size.height - textInsets.top - textInsets.bottom;

Then it becomes easy to scroll:

// if you want scroll animation, use contentOffset
UITextView *textView;
textView.contentOffset = CGPointMake(textView.contentOffset.x, textSize - textViewHeight);

// if you don't want scroll animation
CGRect scrollBounds = textView.bounds;
scrollBounds.origin = CGPointMake(textView.contentOffset.x, textSize - textViewHeight);
textView.bounds = scrollBounds;

Some numbers for reference on what the different sizes represent for an empty UITextView .

textView.frame.size = (width=246, height=50)
textSize = (width=10, height=16.701999999999998)
textView.contentSize = (width=246, height=33)
textView.textContainerInset = (top=8, left=0, bottom=8, right=0)

Answer 26

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 27

Extend UIScrollView to add a scrollToBottom method:

extension UIScrollView {
    func scrollToBottom(animated:Bool) {
        let offset = self.contentSize.height - self.visibleSize.height
        if offset > self.contentOffset.y {
            self.setContentOffset(CGPoint(x: 0, y: offset), animated: animated)
        }
    }
}

Answer 28

To scroll to the bottom end, we have to work with the target view maximum height.

import UIKit

extension UIScrollView {

    func scrollToBottomOf(targetView: UIView, animated: Bool) {
        setContentOffset(CGPoint(x:targetView.frame.minX, y:targetView.frame.maxY), animated: animated)
    }
}

//func invocation example 
optionScrollView.scrollToBottomOf(targetView: self.optionsStackView, animated: false)

Answer 29

As explained here https://janeshswift.com/ios/swift/how-to-scroll-to-a-position-programmatically-in-uiscrollview/

We can create a custom UIScrollView extension as

extension UIScrollView {
    
    func scrollToBottom() {
        let bottomOffset = CGPoint(x: 0, y: self.contentSize.height - self.bounds.height + self.contentInset.bottom)
        self.setContentOffset(bottomOffset, animated: true)
    }
    
    func scrollToTop() {
        let topOffset = CGPoint.zero
        self.setContentOffset(topOffset, animated: true)
    }
    
    
    func scrollToRightEnd(animated: Bool) {
        if self.contentSize.width < self.bounds.size.width { return }
        let rightOffset = CGPoint(x: self.contentSize.width - self.bounds.size.width, y: 0)
        self.setContentOffset(rightOffset, animated: animated)
    }
    
    func scrollToLeftEnd(animated: Bool) {
        if self.contentSize.width < self.bounds.size.width { return }
        let leftOffset = CGPoint.zero
        self.setContentOffset(leftOffset, animated: animated)
    }
    
} 

Use It as --

DispatchQueue.main.async {
    self.itemsScrollView.scrollToBottom()
}

Answer 30

Xamarin.iOS version for UICollectionView of the accepted answer for ease in copying and pasting

var bottomOffset = new CGPoint (0, CollectionView.ContentSize.Height - CollectionView.Frame.Size.Height + CollectionView.ContentInset.Bottom);          
CollectionView.SetContentOffset (bottomOffset, false);

Answer 31

Xamarin.iOS version of accepted answer

var bottomOffset = new CGPoint (0,
     scrollView.ContentSize.Height - scrollView.Frame.Size.Height
     + scrollView.ContentInset.Bottom);

scrollView.SetContentOffset (bottomOffset, false);