UIScrollView scroll to bottom programmatically - ios

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?

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)

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)

Simplest Solution:
[scrollview scrollRectToVisible:CGRectMake(scrollview.contentSize.width - 1,scrollview.contentSize.height - 1, 1, 1) animated:YES];

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)

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)

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];
}

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

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)

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];

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

I also found another useful way of doing this in the case you are using a UITableview (which is a subclass of UIScrollView):
[(UITableView *)self.view scrollToRowAtIndexPath:scrollIndexPath atScrollPosition:UITableViewScrollPositionBottom animated:YES];

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)

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)
}

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];

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)

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];

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];

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)

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];
}

If you don't need animation, this works:
[self.scrollView setContentOffset:CGPointMake(0, CGFLOAT_MAX) animated:NO];

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];
}

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)
}

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)
}

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];

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];

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)

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)
}
}
}

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)

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 scrollToTop(animated: Bool = false) {
setContentOffset(CGPoint(x: contentOffset.x, y: -adjustedContentInset.top), animated: animated)
}
var bottomContentOffsetY: CGFloat {
max(contentSize.height - bounds.height + adjustedContentInset.bottom, -adjustedContentInset.top)
}
func scrollToBottom(animated: Bool = false) {
setContentOffset(CGPoint(x: contentOffset.x, y: bottomContentOffsetY), animated: animated)
}
func scrollToLeading(animated: Bool = false) {
setContentOffset(CGPoint(x: -adjustedContentInset.left, y: contentOffset.y), animated: animated)
}
var trailingContentOffsetX: CGFloat {
max(contentSize.width - bounds.width + adjustedContentInset.right, -adjustedContentInset.left)
}
func scrollToTrailing(animated: Bool = false) {
setContentOffset(CGPoint(x: trailingContentOffsetX, y: contentOffset.y), animated: animated)
}
func scrollViewToVisible(_ view: UIView, animated: Bool = false) {
scrollRectToVisible(convert(view.bounds, from: view), animated: true)
}
var isOnTop: Bool {
contentOffset.y <= -adjustedContentInset.top
}
var isOnBottom: Bool {
contentOffset.y >= bottomContentOffsetY
}
}
Use It as --
DispatchQueue.main.async {
self.itemsScrollView.scrollToBottom()
}

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);

Related

How to make infinity scroll on Scroll View in Xcode project?

I have a Scrollview in my app that shows a few slides,
the default behaviour of the slides are when you reach the last one (ie slide 5 for example) is that it doesn't scroll more to the right,
or when you go to the first one it doesn't scroll more to the left.
how do I make it infinity loop , meaning when I see the last slide, and I scroll more right, it will just scroll to the first one?
(or from the first one left it will scroll to the last one)
here is my scrollViewDidScroll:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let pageIndex = round(scrollView.contentOffset.x/view.frame.width)
pageControl.currentPage = Int(pageIndex)
let maximumHorizontalOffset: CGFloat = scrollView.contentSize.width - scrollView.frame.width
let currentHorizontalOffset: CGFloat = scrollView.contentOffset.x
// vertical
let maximumVerticalOffset: CGFloat = scrollView.contentSize.height - scrollView.frame.height
let currentVerticalOffset: CGFloat = scrollView.contentOffset.y
let percentageHorizontalOffset: CGFloat = currentHorizontalOffset / maximumHorizontalOffset
let percentageVerticalOffset: CGFloat = currentVerticalOffset / maximumVerticalOffset
/*
* below code changes the background color of view on paging the scrollview
*/
// self.scrollView(scrollView, didScrollToPercentageOffset: percentageHorizontalOffset)
/*
* below code scales the imageview on paging the scrollview
*/
let percentOffset: CGPoint = CGPoint(x: percentageHorizontalOffset, y: percentageVerticalOffset)
print ("present offset: ", percentOffset.x)
if(percentOffset.x > 0 && percentOffset.x <= 0.25) {
slides[0].mainPic.transform = CGAffineTransform(scaleX: (0.25-percentOffset.x)/0.25, y: (0.25-percentOffset.x)/0.25)
slides[1].mainPic.transform = CGAffineTransform(scaleX: percentOffset.x/0.25, y: percentOffset.x/0.25)
} else if(percentOffset.x > 0.25 && percentOffset.x <= 0.50) {
slides[1].mainPic.transform = CGAffineTransform(scaleX: (0.50-percentOffset.x)/0.25, y: (0.50-percentOffset.x)/0.25)
slides[2].mainPic.transform = CGAffineTransform(scaleX: percentOffset.x/0.50, y: percentOffset.x/0.50)
} else if(percentOffset.x > 0.50 && percentOffset.x <= 0.75) {
slides[2].mainPic.transform = CGAffineTransform(scaleX: (0.75-percentOffset.x)/0.25, y: (0.75-percentOffset.x)/0.25)
slides[3].mainPic.transform = CGAffineTransform(scaleX: percentOffset.x/0.75, y: percentOffset.x/0.75)
} else if(percentOffset.x > 0.75 && percentOffset.x <= 1) {
slides[3].mainPic.transform = CGAffineTransform(scaleX: (1-percentOffset.x)/0.25, y: (1-percentOffset.x)/0.25)
slides[4].mainPic.transform = CGAffineTransform(scaleX: percentOffset.x, y: percentOffset.x)
}
}
Not sure about your current implementation but your solution will be something like, I'm assuming your slides array contains UIView for each slide. Change the code according to your current implementation.
(void)scrollViewDidScroll:(UIScrollView *)scrollView {
if(if(scrollView.contentOffset.x < 0)) {
CGPoint newOffset = CGPointMake(scrollView.bounds.size.width+scrollView.contentOffset.x, scrollView.contentOffset.y);
[scrollView setContentOffset:newOffset];
[self rotateViewsRight];
}
else if(scrollView.contentOffset.x > scrollView.bounds.size.width*2) {
CGPoint newOffset = CGPointMake(scrollView.contentOffset.x-scrollView.bounds.size.width, scrollView.contentOffset.y);
[scrollView setContentOffset:newOffset];
[self rotateViewsLeft];
}
}
-(void)rotateViewsRight {
UIView *endView = [slides lastObject];
[slides removeLastObject];
[slides insertObject:endView atIndex:0];
[self setContentViewFrames];
}
-(void)rotateViewsLeft {
UIView *endView = slides[0];
[slides removeObjectAtIndex:0];
[slides addObject:endView];
[self setContentViewFrames];
}
-(void) setContentViewFrames {
for(int i = 0; i < 5; i++) {
UIView * view = slides[i];
[view setFrame:CGRectMake(self.view.bounds.size.width*i, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
}
}

How to vertical align (center) the content of UITableView?

I want to center the content of my UITableView that contains headerView and footerView created at storyboard, and UITableViewCells. How can I achieve this?
Here is what I'm trying to implement to solve my problem but this does not work.
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
CGFloat height = self.tableView.frameHeight - self.navigationController.navigationBar.frameHeight - [UIApplication sharedApplication].statusBarFrame.size.height - (self.rowCount * self.rowHeight);
self.tableView.tableHeaderView.frameHeight = height / 2.0;
}
So I subtracted the height of the navigationBar & statusBar and cells' height to the tableView's height to get the height of the empty area.
Now that I get the height if the empty area, I divided it to 2 for the footer and header's view.
In the viewWillAppear and in the didRotateFromInterfaceOrientation functions :
CGFloat headerHeight = (self.view.frame.size.height - (ROW_HEIGHT * [self.tableView numberOfRowsInSection:0]))) / 2;
self.tableView.contentInset = UIEdgeInsetsMake(headerHeight, 0, -headerHeight, 0);
This will solve your problem.
EDIT
Call the updateTableViewContentInset function in the viewWillLayoutSubviews and after each reloadData :
Ojective-C
- (void)updateTableViewContentInset {
CGFloat viewHeight = self.view.frame.size.height;
CGFloat tableViewContentHeight = self.tableView.contentSize.height;
CGFloat marginHeight = (viewHeight - tableViewContentHeight) / 2.0;
self.tableView.contentInset = UIEdgeInsetsMake(marginHeight, 0, -marginHeight, 0);
}
Swift 4
func updateTableViewContentInset() {
let viewHeight: CGFloat = view.frame.size.height
let tableViewContentHeight: CGFloat = tableView.contentSize.height
let marginHeight: CGFloat = (viewHeight - tableViewContentHeight) / 2.0
self.tableView.contentInset = UIEdgeInsets(top: marginHeight, left: 0, bottom: -marginHeight, right: 0)
}
Override viewDidLayoutSubviews and compare the tableView's frame with its contentSize to set its contentInset. In Swift 4 :
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
let tableViewHeight = self.tableView.frame.height
let contentHeight = self.tableView.contentSize.height
let centeringInset = (tableViewHeight - contentHeight) / 2.0
let topInset = max(centeringInset, 0.0)
self.tableView.contentInset = UIEdgeInsets(top: topInset, left: 0.0, bottom: 0.0, right: 0.0)
}
This works well with self-sizing table view cells 👌
Use the contentSize property of UITableView, that how you don't have to take the cell height or count into account.
- (void) updateTableInsetsForHeight: (CGFloat) height
{
CGFloat tableViewInset = MAX((height - self.tableView.contentSize.height) / 2.0, 0.f);
self.tableView.contentInset = UIEdgeInsetsMake(tableViewInset, 0, -tableViewInset, 0);
}
Update the contentInsets after reloading tableView-data, and when the containing view of the tableView becomes visible (viewWillAppear:) and when it changes size (viewWillTransitionToSize:withTransitionCoordinator:).
- (void) viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
{
[self updateTableInsetsForHeight: size.height];
}
Swift 3 based on Pipiks answer
let headerHeight: CGFloat = (view.frame.size.height - CGFloat(Int(tableView.rowHeight) * tableView.numberOfRows(inSection: 0))) / 2
tableView.contentInset = UIEdgeInsetsMake(headerHeight, 0, -headerHeight, 0)
Add a UIView at the top (UIView should be parent of your TableView) of your TableView from storyboard. After that set its constraints to fill the view. Now, set the size of your TableView and set its constraints to center both vertically and horizontally your top
UIView. This will solve your problem.
I found out what causing my computation wrong. The value of self.tableView.bounds.size.height is different from the actual height in viewWillAppear. I used self.view.bounds.size.height instead.
for SWIFT 3 :
var headerHeight: CGFloat = (tableView.frame.size.height - CGFloat(Int(tableView.rowHeight) * tableView.numberOfRows(inSection: 0))) / 2
if headerHeight > 0 {
tableView.contentInset = UIEdgeInsetsMake(headerHeight, 0, 0/*-headerHeight*/, 0)
} else {
headerHeight = 0
tableView.contentInset = UIEdgeInsetsMake(headerHeight, 0, 0/*-headerHeight*/, 0)
}
RESULT :
Set frame of your UITableView like this
CGFloat width = self.view.frame.size.width;
CGFloat height = self.view.frame.size.height;
CGFloat tableHeight = 200.0; //your table height
self.tableView.frame = CGRectMake(0,(height-tableHeight)/2,width,tableHeight);
or try this

Move a view when scrolling in UITableView

I have a UIView with a UITableView below it:
What I would like to do is to have the view above the UITableView move up (out of the way) when the user starts scrolling in the table in order to have more space for the UITableView (and come down when you scroll down again).
I know that this is normally done with a table header view, but my problem is that my table view is inside a tab (actually it is a side-scrolling page view implemented using TTSliddingPageviewcontroller). So while I only have one top UIView there are three UITableViews.
Is it possible to accomplish this manually? My first thought is to put everything in a UIScrollView, but according to Apple's documentation one should never place a UITableView inside a UIScrollView as this leads to unpredictable behavior.
Solution for Swift (Works perfectly with bounce enabled for scroll view):
var oldContentOffset = CGPointZero
let topConstraintRange = (CGFloat(120)..<CGFloat(300))
func scrollViewDidScroll(scrollView: UIScrollView) {
let delta = scrollView.contentOffset.y - oldContentOffset.y
//we compress the top view
if delta > 0 && topConstraint.constant > topConstraintRange.start && scrollView.contentOffset.y > 0 {
topConstraint.constant -= delta
scrollView.contentOffset.y -= delta
}
//we expand the top view
if delta < 0 && topConstraint.constant < topConstraintRange.end && scrollView.contentOffset.y < 0{
topConstraint.constant -= delta
scrollView.contentOffset.y -= delta
}
oldContentOffset = scrollView.contentOffset
}
Since UITableView is a subclass of UIScrollView, your table view's delegate can receive UIScrollViewDelegate methods.
In your table view's delegate:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
static CGFloat previousOffset;
CGRect rect = self.view.frame;
rect.origin.y += previousOffset - scrollView.contentOffset.y;
previousOffset = scrollView.contentOffset.y;
self.view.frame = rect;
}
More simple and fast approach
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
CGRect rect = self.view.frame;
rect.origin.y = -scrollView.contentOffset.y;
self.view.frame = rect;
}
Swift 3 & 4:
var oldContentOffset = CGPoint.zero
let topConstraintRange = (CGFloat(0)..<CGFloat(140))
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let delta = scrollView.contentOffset.y - oldContentOffset.y
//we compress the top view
if delta > 0 && yourConstraint.constant > topConstraintRange.lowerBound && scrollView.contentOffset.y > 0 {
yourConstraint.constant -= delta
scrollView.contentOffset.y -= delta
}
//we expand the top view
if delta < 0 && yourConstraint.constant < topConstraintRange.upperBound && scrollView.contentOffset.y < 0{
yourConstraint.constant -= delta
scrollView.contentOffset.y -= delta
}
oldContentOffset = scrollView.contentOffset
}
I added some constraints to the last solution to prevent some strange behaviours in case of fast scrolling
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let delta = scrollView.contentOffset.y - oldContentOffset.y
//we compress the top view
if delta > 0 && topConstraint.constant > topConstraintRange.lowerBound && scrollView.contentOffset.y > 0 {
searchHeaderTopConstraint.constant = max(topConstraintRange.lowerBound, topConstraint.constant - delta)
scrollView.contentOffset.y -= delta
}
//we expand the top view
if delta < 0 && topConstraint.constant < topConstraintRange.upperBound && scrollView.contentOffset.y < 0 {
topConstraint.constant = min(searchHeaderTopConstraint.constant - delta, topConstraintRange.upperBound)
scrollView.contentOffset.y -= delta
}
oldContentOffset = scrollView.contentOffset
}
Someone asked for the code for my solution so I am posting it here as an answer. The credit for the idea should still go to NobodyNada.
In my UITableViewController I implement this delegate method:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
[[NSNotificationCenter defaultCenter] postNotificationName:#"TableViewScrolled" object:nil userInfo:scrollUserInfo];
}
scrollUserInfo is a NSDictionary where I put my UITableView to pass it with the notification (I do this in viewDidLoad so I only have to do it once):
scrollUserInfo = [NSDictionary dictionaryWithObject:self.tableView forKey:#"scrollView"];
Now, in the view controller that has the view I want to move off screen while scrolling I do this in viewDidLoad:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(handleScroll:) name:#"TableViewScrolled" object:nil];
And finally I have the method:
- (void)handleScroll:(NSNotification *)notification {
UIScrollView *scrollView = [notification.userInfo valueForKey:#"scrollView"];
CGFloat currentOffset = scrollView.contentOffset.y;
CGFloat height = scrollView.frame.size.height;
CGFloat distanceFromBottom = scrollView.contentSize.height - currentOffset;
if (previousOffset < currentOffset && distanceFromBottom > height) {
if (currentOffset > viewHeight)
currentOffset = viewHeight;
self.topVerticalConstraint.constant += previousOffset - currentOffset;
previousOffset = currentOffset;
}
else {
if (previousOffset > currentOffset) {
if (currentOffset < 0)
currentOffset = 0;
self.topVerticalConstraint.constant += previousOffset - currentOffset;
previousOffset = currentOffset;
}
}
}
previousOffset is an instance variable CGFloat previousOffset;.
topVerticalConstraint is a NSLayoutConstraint that is set as a IBOutlet. It goes from the top of the view to the top of its superview and the initial value is 0.
It's not perfect. For instance, if the user scrolls very aggressively up the movement of the view can get a bit jerky. The issue is worse for large views; if the view is small enough there is no problem.
To create like this animation,
lazy var redView: UIView = {
let view = UIView(frame: CGRect(x: 0, y: 0, width:
self.view.frame.width, height: 100))
view.backgroundColor = .red
return view
}()
var pageMenu: CAPSPageMenu?
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(redView)
let rect = CGRect(x: 0, y: self.redView.frame.maxY, width: self.view.bounds.size.width, height:(self.view.bounds.size.height - (self.redView.frame.maxY)))
pageMenu?.view.frame = rect
self.view.addSubview(pageMenu!.view)
}
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offset = scrollView.contentOffset.y
if(offset > 100){
self.redView.frame = CGRect(x: 0, y: 0, width: self.view.bounds.size.width, height: 0)
}else{
self.redView.frame = CGRect(x: 0, y: 0, width: self.view.bounds.size.width, height: 100 - offset)
}
let rect = CGRect(x: 0, y: self.redView.frame.maxY, width: self.view.bounds.size.width, height:(self.view.bounds.size.height - (self.redView.frame.maxY)))
pageMenu?.view.frame = rect
}
you must change pageMenu.view with your collectionView/tableView
I know this post in very old. I tried above solutions but neither worked for me for tried my own, hopefully it can help you. This scenario is pretty common, as apple suggested not to use TableViewController inside any ScrollView because the compiler will confused as in whom to respond becuase it will be getting two delegate call back - one from ScrollViewDelegate and another from UITableViewDelegate.
Instead we can use ScrollViewDelegate and disable the UITableViewScrolling.
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
CGFloat currentOffSetY = scrollView.contentOffset.y;
CGFloat diffOffset = self.lastContentOffset - currentOffSetY;
self.scrollView.contentSize = CGSizeMake(self.scrollView.contentSize.width, 400 + [self.tableView contentSize].height);
if (self.lastContentOffset < scrollView.contentOffset.y) {
tableView.frame = CGRectMake(tableView.frame.origin.x, tableView.frame.origin.y , tableView.frame.size.width, tableView.size.height - diffOffset);
}
if (self.lastContentOffset > scrollView.contentOffset.y) {
tableView.frame = CGRectMake(tableView.frame.origin.x, tableViewframe.origin.y, tableViewframe.size.width, tableView.frame.size.height + diffOffset);
}
self.lastContentOffset = currentOffSetY;
}
Here lastContentOffset is CGFloat defined as property
The View Heirarchy is as follows:
ViewController --> View contains ScrollView (whose delegate method is defined above) --> Contain TableView.
By the above code we are manually increasing and decreasing the height of the table view along with the content size of ScrollView.
Remember to disable the Scrolling of TableView.
You can make it like this:
Add these as your class variables:
private let NUMBER_OF_ROWS: Int = 256
private let ROW_HEIGHT: CGFloat = 75.0
private let MINIMUM_CONSTANT_VALUE: CGFloat = -150.0 /// This is the hidable view's height
#IBOutlet weak var hidableViewTopConstraint: NSLayoutConstraint! /// This is an outlet from your storyboard
private var lastContentOffset: CGFloat = 0.0
This goes on your viewDidLoad():
tableView.delegate = self
And then you add this as an extension for your view controller:
extension ViewController: UIScrollViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let delta = tableView.contentOffset.y - lastContentOffset
let canScrollUp: Bool =
delta < 0 &&
hidableViewTopConstraint.constant < 0 &&
scrollView.contentOffset.y < 0
let canScrollDown: Bool =
delta > 0 &&
hidableViewTopConstraint.constant > MINIMUM_CONSTANT_VALUE &&
tableView.contentOffset.y > 0
if canScrollUp || canScrollDown{
hidableViewTopConstraint.constant -= delta
tableView.contentOffset.y -= delta
}
lastContentOffset = tableView.contentOffset.y
}
}
But note that the scroll mechanism will only work when the TableView is scrolled. The top view wont collapse or expand if you scroll it.
I made an example project you can check, it is called iOSFixedHeaderList

Resize UITableView height, and keep scrolled at bottom

Im trying to resize the tableview's height with a animation, it works fine by animating the tableview's frame.size.height.
The problem is, i have a tableview that is 200px height and scrolled to the bottom, i want to animate this to 100px, i run a simple
[UIView animateWithDuration:0.245f animations:^{
CGRect frame = tableview.frame;
frame.size.height = 100.f;
tableview.frame = frame;
}];
this works fine, but after i resized it it is no longer scrolled to the bottom of the tableview. i want the tableview to always be scrolled at the bottom while animating. i tried alot of differnet things like calling
[tablview scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:YES];
right before/after i start the resize animation, but i have not managed to get them to sync 100%. Is there a way to resize the tableview while the bottom of the tableview displays the last element of the scrollview.
I found a solution for my problem, there might very well be a better solution but this actually works quite well :)
Before i start animating i see if the contentSize.height is larger than the target height, if so i do following:
if (mMessages.contentSize.height > 150.f)
{
CGFloat expandedOffsetY = 52.f;
CGFloat collapsedBottomOffset = (150.f + 18.f);
CGFloat expandedBottomOffset = (MIN(320.f, mMessages.contentSize.height) + expandedOffsetY);
tableFrame.origin.y = (collapsedBottomOffset - expandedBottomOffset) + expandedOffsetY;
}
else
{
tableFrame.origin.y = 18.f;
tableFrame.size.height = 150.f;
}
this will put the tableview in a minus origin.y, then i have wrapped the tableview inside a "parent" uiview with clip sub views = YES.
Then i have a "completed" animation block that "resets" to the target values.
CGRect tableFrame = mMessages.frame;
tableFrame.origin.y = 18.f;
tableFrame.size.height = 150.f;
mMessages.frame = tableFrame;
if (mMessages.contentSize.height > tableFrame.size.height)
{
float contentOffsetY = mMessages.contentSize.height - tableFrame.size.height;
mMessages.contentOffset = CGPointMake(0.0f, contentOffsetY);
}
Try updating the contentOffset of the table view as you animate the frame.
[UIView animateWithDuration:0.245f animations:^{
CGRect frame = tableview.frame;
frame.size.height = 100.f;
tableview.frame = frame;
float contentOffsetY = tableview.contentSize - tableview.frame.size.height;
tableview.contentOffset = CGPointMake(0, contentOffsetY);
}];
[UIView animateWithDuration:0.245f animations:^{
CGRect frame = tableview.frame;
frame.size.height = 100.f;
tableview.frame = frame;
} completion:^(BOOL finished) {
// Find your last indexpath
[tablview scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:YES];
} ];
Scrolling the tableview to the bottom in the animation block was working for me, with one little twist: when I reduced the hight of the tableView I called scrollToIndexPath without animating, and when I expand the tableView I called the scrollToIndexPath with animation.
UIView.animate(withDuration: 0.25) { [weak self] in
guard let strongSelf = self
else { return }
// ...
// updateConstraints
// ...
strongSelf.view.layoutIfNeeded()
if reduceSize {
tableView.scrollToLastRow(animated: false)
} else {
tableView.scrollToLastRow(animated: true)
}
}
Extension for UITableView
extension UITableView {
func scrollToLastRow(animated: Bool) {
let lastSection = numberOfSections-1
let lastRow = numberOfRows(inSection: lastSection)-1
let lastIndexPath = IndexPath(row: lastRow, section: lastSection)
scrollToRow(at: lastIndexPath, at: .bottom, animated: animated)
}
}

How to know when UITableView did scroll to bottom in iPhone?

I would like to know when a UITableView did scroll to bottom in order to load and show more content, something like a delegate or something else to let the controller know when the table did scroll to bottom.
How can I do this?
in the tableview delegate do something like this
ObjC:
- (void)scrollViewDidScroll:(UIScrollView *)aScrollView {
CGPoint offset = aScrollView.contentOffset;
CGRect bounds = aScrollView.bounds;
CGSize size = aScrollView.contentSize;
UIEdgeInsets inset = aScrollView.contentInset;
float y = offset.y + bounds.size.height - inset.bottom;
float h = size.height;
// NSLog(#"offset: %f", offset.y);
// NSLog(#"content.height: %f", size.height);
// NSLog(#"bounds.height: %f", bounds.size.height);
// NSLog(#"inset.top: %f", inset.top);
// NSLog(#"inset.bottom: %f", inset.bottom);
// NSLog(#"pos: %f of %f", y, h);
float reload_distance = 10;
if(y > h + reload_distance) {
NSLog(#"load more rows");
}
}
Swift:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offset = scrollView.contentOffset
let bounds = scrollView.bounds
let size = scrollView.contentSize
let inset = scrollView.contentInset
let y = offset.y + bounds.size.height - inset.bottom
let h = size.height
let reload_distance:CGFloat = 10.0
if y > (h + reload_distance) {
print("load more rows")
}
}
Modified neoneyes answer a bit.
This answer targets those of you who only wants the event to be triggered once per release of the finger.
Suitable when loading more content from some content provider (web service, core data etc).
Note that this approach does not respect the response time from your web service.
- (void)scrollViewDidEndDragging:(UIScrollView *)aScrollView
willDecelerate:(BOOL)decelerate
{
CGPoint offset = aScrollView.contentOffset;
CGRect bounds = aScrollView.bounds;
CGSize size = aScrollView.contentSize;
UIEdgeInsets inset = aScrollView.contentInset;
float y = offset.y + bounds.size.height - inset.bottom;
float h = size.height;
float reload_distance = 50;
if(y > h + reload_distance) {
NSLog(#"load more rows");
}
}
add this method in the UITableViewDelegate:
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
CGFloat height = scrollView.frame.size.height;
CGFloat contentYoffset = scrollView.contentOffset.y;
CGFloat distanceFromBottom = scrollView.contentSize.height - contentYoffset;
if(distanceFromBottom < height)
{
NSLog(#"end of the table");
}
}
None of the answers above helped me, so I came up with this:
- (void)scrollViewDidEndDecelerating:(UIScrollView *)aScrollView
{
NSArray *visibleRows = [self.tableView visibleCells];
UITableViewCell *lastVisibleCell = [visibleRows lastObject];
NSIndexPath *path = [self.tableView indexPathForCell:lastVisibleCell];
if(path.section == lastSection && path.row == lastRow)
{
// Do something here
}
}
The best way is to test a point at the bottom of the screen and use this method call when ever the user scrolls (scrollViewDidScroll):
- (NSIndexPath *)indexPathForRowAtPoint:(CGPoint)point
Test a point near the bottom of the screen, and then using the indexPath it returns check if that indexPath is the last row then if it is, add rows.
Use – tableView:willDisplayCell:forRowAtIndexPath: (UITableViewDelegate method)
Simply compare the indexPath with the items in your data array (or whatever data source you use for your table view) to figure out if the last element is being displayed.
Docs: http://developer.apple.com/library/ios/documentation/uikit/reference/UITableViewDelegate_Protocol/Reference/Reference.html#//apple_ref/occ/intfm/UITableViewDelegate/tableView:willDisplayCell:forRowAtIndexPath:
UITableView is a subclass of UIScrollView, and UITableViewDelegate conforms to UIScrollViewDelegate. So the delegate you attach to the table view will get events such as scrollViewDidScroll:, and you can call methods such as contentOffset on the table view to find the scroll position.
NSLog(#"%f / %f",tableView.contentOffset.y, tableView.contentSize.height - tableView.frame.size.height);
if (tableView.contentOffset.y == tableView.contentSize.height - tableView.frame.size.height)
[self doSomething];
Nice and simple
in Swift you can do something like this. Following condition will be true every time you reach end of the tableview
func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
if indexPath.row+1 == postArray.count {
println("came to last row")
}
}
Building on #Jay Mayu's answer, which I felt was one of the better solutions:
Objective-C
// UITableViewDelegate
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
// Need to call the service & update the array
if(indexPath.row + 1 == self.sourceArray.count) {
DLog(#"Displayed the last row!");
}
}
Swift 2.x
// UITableViewDelegate
func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
if (indexPath.row + 1) == sourceArray.count {
print("Displayed the last row!")
}
}
Here is the swift 3.0 version code.
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offset = scrollView.contentOffset
let bounds = scrollView.bounds
let size = scrollView.contentSize
let inset = scrollView.contentInset
let y: Float = Float(offset.y) + Float(bounds.size.height) + Float(inset.bottom)
let height: Float = Float(size.height)
let distance: Float = 10
if y > height + distance {
// load more data
}
}
I generally use this to load more data , when last cell starts display
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.row == myDataArray.count-1) {
NSLog(#"load more");
}
}
Taking neoneye excellent answers but in swift, and renaming of the variables..
Basically we know we have reached the bottom of the table view if the yOffsetAtBottom is beyond the table content height.
func isTableViewScrolledToBottom() -> Bool {
let tableHeight = tableView.bounds.size.height
let contentHeight = tableView.contentSize.height
let insetHeight = tableView.contentInset.bottom
let yOffset = tableView.contentOffset.y
let yOffsetAtBottom = yOffset + tableHeight - insetHeight
return yOffsetAtBottom > contentHeight
}
My solution is to add cells before tableview will decelerate on estimated offset. It's predictable on by velocity.
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)offset {
NSLog(#"offset: %f", offset->y+scrollView.frame.size.height);
NSLog(#"Scroll view content size: %f", scrollView.contentSize.height);
if (offset->y+scrollView.frame.size.height > scrollView.contentSize.height - 300) {
NSLog(#"Load new rows when reaches 300px before end of content");
[[DataManager shared] fetchRecordsNextPage];
}
}
Update for Swift 3
Neoneye's answer worked best for me in Objective C, this is the equivalent of the answer in Swift 3:
func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
let offset: CGPoint = scrollView.contentOffset
let bounds: CGRect = scrollView.bounds
let size: CGSize = scrollView.contentSize
let inset: UIEdgeInsets = scrollView.contentInset
let y: CGFloat = offset.y + bounds.size.height - inset.bottom
let h: CGFloat = size.height
// print("offset: %f", offset.y)
// print("content.height: %f", size.height)
// print("bounds.height: %f", bounds.size.height)
// print("inset.top: %f", inset.top)
// print("inset.bottom: %f", inset.bottom)
// print("position: %f of %f", y, h)
let reloadDistance: CGFloat = 10
if (y > h + reloadDistance) {
print("load more rows")
}
}
I want perform some action on my any 1 full Tableviewcell.
So the code is link the :
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
NSArray* cells = self.tableView.visibleCells;
NSIndexPath *indexPath = nil ;
for (int aIntCount = 0; aIntCount < [cells count]; aIntCount++)
{
UITableViewCell *cell = [cells objectAtIndex:aIntCount];
CGRect cellRect = [self.tableView convertRect:cell.frame toView:self.tableView.superview];
if (CGRectContainsRect(self.tableView.frame, cellRect))
{
indexPath = [self.tableView indexPathForCell:cell];
// remain logic
}
}
}
May this is help to some one.
#neoneye's answer worked for me. Here is the Swift 4 version of it
let offset = scrollView.contentOffset
let bounds = scrollView.bounds
let size = scrollView.contentSize
let insets = scrollView.contentInset
let y = offset.y + bounds.size.height - insets.bottom
let h = size.height
let reloadDistance = CGFloat(10)
if y > h + reloadDistance {
//load more rows
}

Resources