This question already has an answer here:
I have implemented a UIPageViewController that contains two pages. On the right most page, I am able to swipe to the right, and pull the page back so that when I release, it bounces back. The same thing occurs on the left page when I swipe to the left. (The bouncing is like what happens when you reach the bottom of a safari page)
Is there a way to disable the bounce effect? Thanks!
Thus far, none of the answers actually work fully. The edge case that they all fail on is this:
In that situation, every solution I've seen so far goes past the bounds of page 0. The core problem is that the underlying API is broken, and begins reporting a content offset relative to page 0 without calling our callback to let us know that it is showing a different page. Throughout this process, the API still claims to be showing page 1, going towards page zero even while it is really on page zero going towards page -1.
The workaround for this design flaw is remarkably ugly, but here it is:
@property (weak,nonatomic) UIPageControl *pageControl;
@property (nonatomic,assign) BOOL shouldBounce;
@property (nonatomic,assign) CGFloat lastPosition;
@property (nonatomic,assign) NSUInteger currentIndex;
@property (nonatomic,assign) NSUInteger nextIndex;
- (void)viewDidLoad {
[super viewDidLoad];
...
self.shouldBounce = NO;
for (id testView in self.pageController.view.subviews) {
UIScrollView *scrollView = (UIScrollView *)testView;
if ([scrollView isKindOfClass:[UIScrollView class]]) {
scrollView.delegate = self;
// scrollView.bounces = self.shouldBounce;
}
}
}
- (NSInteger)presentationIndexForPageViewController:(UIPageViewController *)pageViewController{
return (NSInteger)self.currentIndex;
}
- (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers{
id controller = [pendingViewControllers firstObject];
self.nextIndex = [viewControllers indexOfObject:controller];
}
- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed{
if(completed) {
// At this point, we can safely query the API to ensure
// that we are fully in sync, just in case.
self.currentIndex = [viewControllers indexOfObject:[pageViewController.viewControllers objectAtIndex:0]];
[self.pageControl setCurrentPage:self.currentIndex];
}
self.nextIndex = self.currentIndex;
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
/* The iOS page view controller API is broken. It lies to us and tells us
that the currently presented view hasn't changed, but under the hood, it
starts giving the contentOffset relative to the next view. The only
way to detect this brain damage is to notice that the content offset is
discontinuous, and pretend that the page changed.
*/
if (self.nextIndex > self.currentIndex) {
/* Scrolling forwards */
if (scrollView.contentOffset.x < (self.lastPosition - (.9 * scrollView.bounds.size.width))) {
self.currentIndex = self.nextIndex;
[self.pageControl setCurrentPage:self.currentIndex];
}
} else {
/* Scrolling backwards */
if (scrollView.contentOffset.x > (self.lastPosition + (.9 * scrollView.bounds.size.width))) {
self.currentIndex = self.nextIndex;
[self.pageControl setCurrentPage:self.currentIndex];
}
}
/* Need to calculate max/min offset for *every* page, not just the first and last. */
CGFloat minXOffset = scrollView.bounds.size.width - (self.currentIndex * scrollView.bounds.size.width);
CGFloat maxXOffset = (([viewControllers count] - self.currentIndex) * scrollView.bounds.size.width);
NSLog(@"Page: %ld NextPage: %ld X: %lf MinOffset: %lf MaxOffset: %lf\n", (long)self.currentIndex, (long)self.nextIndex,
(double)scrollView.contentOffset.x,
(double)minXOffset, (double)maxXOffset);
if (!self.shouldBounce) {
CGRect scrollBounds = scrollView.bounds;
if (scrollView.contentOffset.x <= minXOffset) {
scrollView.contentOffset = CGPointMake(minXOffset, 0);
// scrollBounds.origin = CGPointMake(minXOffset, 0);
} else if (scrollView.contentOffset.x >= maxXOffset) {
scrollView.contentOffset = CGPointMake(maxXOffset, 0);
// scrollBounds.origin = CGPointMake(maxXOffset, 0);
}
[scrollView setBounds:scrollBounds];
}
self.lastPosition = scrollView.contentOffset.x;
}
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
/* Need to calculate max/min offset for *every* page, not just the first and last. */
CGFloat minXOffset = scrollView.bounds.size.width - (self.currentIndex * scrollView.bounds.size.width);
CGFloat maxXOffset = (([viewControllers count] - self.currentIndex) * scrollView.bounds.size.width);
if (!self.shouldBounce) {
if (scrollView.contentOffset.x <= minXOffset) {
*targetContentOffset = CGPointMake(minXOffset, 0);
} else if (scrollView.contentOffset.x >= maxXOffset) {
*targetContentOffset = CGPointMake(maxXOffset, 0);
}
}
}
Basically, it records the offset for each scroll event. If the scroll position has moved a distance that is impossible (I arbitrarily picked 90% of the width of the screen) in the opposite direction from the direction of scrolling, the code assumes that iOS is lying to us, and behaves as though the transition finished properly, treating the offsets as being relative to the new page instead of the old one.
Here a simple solution
fileprivate var currentIndex = 0
fileprivate var lastPosition: CGFloat = 0
override func viewDidLoad() {
super.viewDidLoad()
for view in view.subviews {
if view is UIScrollView {
(view as! UIScrollView).delegate = self
break
}
}
}
func pageViewController(_ pageViewController: UIPageViewController,
didFinishAnimating finished: Bool,
previousViewControllers: [UIViewController],
transitionCompleted completed: Bool) {
if completed {
// Get current index
let pageContentViewController = pageViewController.viewControllers![0]
currentIndex = orderedViewControllers.index(of: pageContentViewController)!
}
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
self.lastPosition = scrollView.contentOffset.x
if (currentIndex == orderedViewControllers.count - 1) && (lastPosition > scrollView.frame.width) {
scrollView.contentOffset.x = scrollView.frame.width
return
} else if currentIndex == 0 && lastPosition < scrollView.frame.width {
scrollView.contentOffset.x = scrollView.frame.width
return
}
}
Also the trick, but i think it's better then dealing with pageViewController.view.subviews array
1) put your UIPageViewController on UIScrollView
2) content width have to be larger then scrollview width, for example by 10.0f
self.scrollView.contentSize = CGSizeMake(self.scrollView.frame.size.width + 10.0f, self.scrollView.frame.size.height);
3) set scroll view bounce - NO
4) set scrollview delegate, and implement
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
scrollView.contentOffset = CGPointMake(0.0, 0.0);
}
Here is @SahilS solution implemented in Swift.
It however seems to be buggy for me.
override func viewDidLoad() {
super.viewDidLoad()
for view in view.subviews {
if view is UIScrollView {
(view as! UIScrollView).delegate = self
break
}
}
extension PageViewController: UIPageViewControllerDelegate, UIPageViewControllerDataSource {
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
guard let viewControllerIndex = orderedViewControllers?.index(of: viewController) else {
return nil
}
let previousIndex = viewControllerIndex - 1
guard previousIndex >= 0 else {
return nil
}
guard (orderedViewControllers?.count)! > previousIndex else {
return nil
}
print("in viewControllerBefore")
return orderedViewControllers?[previousIndex]
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
guard let viewControllerIndex = orderedViewControllers?.index(of: viewController) else {
return nil
}
let nextIndex = viewControllerIndex + 1
let orderedViewControllersCount = orderedViewControllers?.count
guard orderedViewControllersCount != nextIndex else {
return nil
}
print("in viewControllerAfter")
return orderedViewControllers?[nextIndex]
}
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if completed {
// Get current index
let pageContentViewController = pageViewController.viewControllers![0]
currentIndex = (orderedViewControllers?.index(of: pageContentViewController))!
}
self.nextIndex = self.currentIndex
}
func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {
print("willTransitionTo")
let controller = pendingViewControllers.first
if let i = viewControllers?.index(of: controller!) {
print("Jason is at index \(i)")
self.currentIndex = i
} else {
print("Jason isn't in the array")
}
}
func presentationIndex(for pageViewController: UIPageViewController) -> Int {
return self.currentIndex
}
}
extension PageViewController: UIScrollViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
/* The iOS page view controller API is broken. It lies to us and tells us
that the currently presented view hasn't changed, but under the hood, it
starts giving the contentOffset relative to the next view. The only
way to detect this brain damage is to notice that the content offset is
discontinuous, and pretend that the page changed.
*/
let poop = self.lastPosition + (0.9 * scrollView.bounds.size.width)
print("poop is \(poop)")
if (self.nextIndex > self.currentIndex) {
/* Scrolling forwards */
if (scrollView.contentOffset.x < (self.lastPosition - (0.9 * scrollView.bounds.size.width))) {
self.currentIndex = self.nextIndex;
}
} else {
/* Scrolling backwards */
if (scrollView.contentOffset.x > (self.lastPosition + (0.9 * scrollView.bounds.size.width))) {
self.currentIndex = self.nextIndex;
}
}
/* Need to calculate max/min offset for *every* page, not just the first and last. */
let minXOffset = scrollView.bounds.size.width - (CGFloat(self.currentIndex) * scrollView.bounds.size.width);
let maxXOffset = (CGFloat(((viewControllers?.count)! - self.currentIndex)) * scrollView.bounds.size.width)
if (!self.shouldBounce) {
let scrollBounds = scrollView.bounds;
if (scrollView.contentOffset.x <= minXOffset) {
scrollView.contentOffset = CGPoint(x: minXOffset, y: 0)
} else if (scrollView.contentOffset.x >= maxXOffset) {
scrollView.contentOffset = CGPoint(x: maxXOffset, y: 0)
}
scrollView.bounds = scrollBounds
}
self.lastPosition = scrollView.contentOffset.x
}
func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
var scrollOffset = targetContentOffset.pointee
let minXOffset = scrollView.bounds.size.width - (CGFloat(self.currentIndex) * scrollView.bounds.size.width);
let maxXOffset = (CGFloat(((viewControllers?.count)! - self.currentIndex)) * scrollView.bounds.size.width)
if (!self.shouldBounce) {
if (scrollView.contentOffset.x <= minXOffset) {
scrollOffset = CGPoint(x: minXOffset, y: 0)
} else if (scrollView.contentOffset.x >= maxXOffset) {
scrollOffset = CGPoint(x: maxXOffset, y: 0)
}
}
}
}
for (UIView *view in self.pageViewController.view.subviews ) {
if ([view isKindOfClass:[UIScrollView class]]) {
UIScrollView *scroll = (UIScrollView *)view;
scroll.bounces = NO;
}
}
It's kinda hacky though -- that's probably why the original answer here got downvoted.
I made it.
If you want to disable the bouncing effect of UIPageViewController for the 1st page (bounce on the left) and the last page (bounce on the right), the idea is to implement the underlying scrollView's delegate:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
To implement the delegate, you can
The implementation for scrollViewDidScroll is to reset the contentOffset to the origin (NOT (0,0), but (bound.size.width, 0)) when the user is reaching out of the bounds, like this:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if (NO == isPageToBounce) {
if (_currentPage == 0 && scrollView.contentOffset.x < scrollView.bounds.size.width) {
scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0);
}
if (_currentPage == [listVCs count]-1 && scrollView.contentOffset.x > scrollView.bounds.size.width) {
scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0);
}
}
// more
}
And the implementation for scrollViewWillEndDragging is to deal with a bug scenario when the user quickly swipes from left to right at the fist page, the first page won't bounce at the left (due to the function above), but will bounce at the right caused by the (maybe) velocity of the swipe. And finally when bounced back, the UIPageViewController will trigger a page flip to the 2nd page (which is, of cause, not expected).
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
if (NO == isPageToBounce) {
if (_currentPage == 0 && scrollView.contentOffset.x <= scrollView.bounds.size.width) {
velocity = CGPointZero;
*targetContentOffset = CGPointMake(scrollView.bounds.size.width, 0);
}
if (_currentPage == [listVCs count]-1 && scrollView.contentOffset.x >= scrollView.bounds.size.width) {
velocity = CGPointZero;
*targetContentOffset = CGPointMake(scrollView.bounds.size.width, 0);
}
}
}
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