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Disable UIPageViewController bounce

由 两盒软妹~` 提交于 2019-11-26 17:26:38

问题


Searched a lot for this one, but couldn't find a proper solution yet.

Is it possible to disable the bounce effect of a UIPageViewController and still use the UIPageViewControllerTransitionStyleScroll?


回答1:


Disable UIPageViewController's bounce

  1. Add the <UIScrollViewDelegate> delegate to your UIPageViewController's header

  2. Set the UIPageViewController's underlying UIScrollView's delegates to their parent in viewDidLoad:

    for (UIView *view in self.view.subviews) {
    if ([view isKindOfClass:[UIScrollView class]]) {
        ((UIScrollView *)view).delegate = self;
        break;
    }
}

  3. 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 (_currentPage == 0 && scrollView.contentOffset.x < scrollView.bounds.size.width) {
        scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0);
    } else if (_currentPage == totalViewControllersInPageController-1 && scrollView.contentOffset.x > scrollView.bounds.size.width) {
        scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0);
    }
}

  4. Finally, the implementation for scrollViewWillEndDragging is to deal with a bug scenario when the user quickly swipes from left to right at the first 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 course, not expected).

    - (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
    if (_currentPage == 0 && scrollView.contentOffset.x <= scrollView.bounds.size.width) {
        *targetContentOffset = CGPointMake(scrollView.bounds.size.width, 0);
    } else if (_currentPage == totalViewControllersInPageController-1 && scrollView.contentOffset.x >= scrollView.bounds.size.width) {
        *targetContentOffset = CGPointMake(scrollView.bounds.size.width, 0);
    }
}

Swift 4.0

Code to put into viewDidLoad:

for subview in self.view.subviews {
    if let scrollView = subview as? UIScrollView {
        scrollView.delegate = self
        break;
    }
}

Implementation for scrollViewDidScroll:

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if (currentPage == 0 && scrollView.contentOffset.x < scrollView.bounds.size.width) {
        scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0);
    } else if (currentPage == totalViewControllersInPageController - 1 && scrollView.contentOffset.x > scrollView.bounds.size.width) {
        scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0);
    }
}

Implementation for scrollViewWillEndDragging:

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    if (currentPage == 0 && scrollView.contentOffset.x <= scrollView.bounds.size.width) {
        targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0);
    } else if (currentPage == totalViewControllersInPageController - 1 && scrollView.contentOffset.x >= scrollView.bounds.size.width) {
        targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0);
    }
}



回答2:


Disable UIPageViewController's bounce

Swift 2.2

Addition to answers

1) Add UIScrollViewDelegate to UIPageViewController

extension PageViewController: UIScrollViewDelegate

2) Add to viewDidLoad

for view in self.view.subviews {
   if let scrollView = view as? UIScrollView {
      scrollView.delegate = self
   }
}

3) Add UIScrollViewDelegate methods

func scrollViewDidScroll(scrollView: UIScrollView) {
    if currentIndex == 0 && scrollView.contentOffset.x < scrollView.bounds.size.width {
        scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
    } else if currentIndex == totalViewControllers - 1 && scrollView.contentOffset.x > scrollView.bounds.size.width {
        scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
    }
}

func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    if currentIndex == 0 && scrollView.contentOffset.x < scrollView.bounds.size.width {
        scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
    } else if currentIndex == totalViewControllers - 1 && scrollView.contentOffset.x > scrollView.bounds.size.width {
        scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
    }
}



回答3:


I wasn't sure how to correctly manage the currentIndex but ended up doing 

extension Main: UIPageViewControllerDelegate {
    func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        if completed {
            guard let viewController = pageViewController.viewControllers?.first,
                index = viewControllerDatasource.indexOf(viewController) else {
                fatalError("Can't prevent bounce if there's not an index")
            }
            currentIndex = index
        }
    }
}



回答4:


UIPageViewController doesn't actually do much for you. You can use a UIScrollView with view controllers quite easily, and disable the bounce on that.

Just do something like

int x=0;
for (NSString *storyboardID in storyboardIDs){
        UIViewController *vc = [storyboard instantiateViewControllerWithIdentifier:storyboardID];
        [self addChildViewController:vc];
        vc.view.frame = CGRectMake(x++*vc.view.frame.size.width, 0, vc.view.frame.size.width, vc.view.frame.size.height);
        [self.scrollView addSubview:vc.view];
        [vc didMoveToParentViewController:self];
        self.scrollView.contentSize = CGSizeMake(storyboardIDs.count*vc.view.frame.size.width, vc.view.frame.size.height);
}



回答5:


Another option is to set ScrollView.bounce = false. It solved my problem with pageViewController's(Of course not about ScrollView) scrolling bounce. Bounce is disabled, and all page can scroll without bounces.




回答6:


Edit: Do not use this solution. I learned afterwards that this introduces a bug where about 5% of the time, the user can't page in the same direction. They have to page back, then forward again to continue.

If you're using a UIPageViewControllerDataSource, a relatively simple workaround (and a bit hacky) is to disable bouncing each time the pageViewController:viewControllerBeforeViewController: delegate method is called. Here is an example implementation:

@interface YourDataSourceObject ()
@property (strong, nonatomic) UIScrollView *scrollView;
@end

@implementation
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {
    if (!self.scrollView) {
        for (UIView *view in pageViewController.view.subviews) {
            if ([view isKindOfClass:[UIScrollView class]]) {
                self.scrollView = (UIScrollView *)view;
            }
        }
    }
    self.scrollView.bounces = NO;

    // Your other logic to return the correct view controller. 
}
@end



回答7:


If you will try to disable bounce for UIPageViewController.scrollView, you will definitely get a broken pageViewController: swipe ain't gonna work. So, don't do that:

self.theScrollView.alwaysBounceHorizontal = NO;
self.theScrollView.bounces = NO;

Use the solution with searching scrollView reference in UIPageViewController subviews only for disabling scroll entirely:

@interface MyPageViewController : UIPageViewController
@property (nonatomic, assign) BOOL scrollEnabled;
@end

@interface MyPageViewController ()
@property (nonatomic, weak) UIScrollView *theScrollView;
@end

@implementation MyPageViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    for (UIView *view in self.view.subviews) {
        if ([view isKindOfClass:UIScrollView.class]) {
            self.theScrollView = (UIScrollView *)view;
            break;
        }
    }
}

- (void)setScrollEnabled:(BOOL)scrollEnabled
{
    _scrollEnabled = scrollEnabled;
    self.theScrollView.scrollEnabled = scrollEnabled;
}

@end

Solution for disabling bounce at UIPageViewController:

  1. Create UIScrollView category (for ex. CustomScrolling). UIScrollView is delegate of their gesture recognizer already.
  2. Be aware that your target UIViewController (aka baseVC with UIPageViewController inside) shared via AppDelegate. Otherwise you can use run-time (#import <objc/runtime.h>) and add reference property (to your controller baseVC) to the category.

  3. Implement category:

    @interface UIScrollView (CustomScrolling) <UIGestureRecognizerDelegate>
@end

@implementation UIScrollView (CustomScrolling)

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    UIViewController * baseVC = [(AppDelegate *)[[UIApplication sharedApplication] delegate] baseVC];
    if (gestureRecognizer.view == baseVC.pageViewController.theScrollView) {
        NSInteger page = [baseVC selectedIndex];
        NSInteger total = [baseVC viewControllers].count;
        UIPanGestureRecognizer *recognizer = (UIPanGestureRecognizer *)gestureRecognizer;
        CGPoint velocity = [recognizer velocityInView:self];
        BOOL horizontalSwipe = fabs(velocity.x) > fabs(velocity.y);
        if (!horizontalSwipe) {
            return YES;
        }
        BOOL scrollingFromLeftToRight = velocity.x > 0;
        if ((scrollingFromLeftToRight && page > 0) || (!scrollingFromLeftToRight && page < (total - 1))) {
            return YES;
        }
        return NO;
    }
    return YES;
}

@end

  4. Import category file #import "UIScrollView+CustomScrolling.h" in your baseVC, that uses UIPageViewController.




回答8:


@Dong Ma's approach is perfect but it can be a little bit improved and simplified.

Code to put into viewDidLoad:

for subview in view.subviews {
    if let scrollView = subview as? UIScrollView {
        scrollView.delegate = self
        break
    }
}

Implementation for scrollViewDidScroll:

public func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if (currentPage == 0 && scrollView.contentOffset.x < scrollView.bounds.size.width) || (currentPage == totalNumberOfPages - 1 && scrollView.contentOffset.x > scrollView.bounds.size.width) {
      scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
    }
  }

Implementation for scrollViewWillEndDragging:

public func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    if (currentPage == 0 && scrollView.contentOffset.x <= scrollView.bounds.size.width) || (currentPage == totalNumberOfPages - 1 && scrollView.contentOffset.x >= scrollView.bounds.size.width) {
      targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
    }
  }



回答9:


Edited answer of Dong Ma, where:

  • added - respects layout direction (Hebrew for example)
  • fixed - wrong counting currentIndex when swipes very quick

Info:

  • Written in Swift 5.0
  • Builded and tested in Xcode 10.2.1
  • iOS 12.0

How to:

  1. Let's assume we have a UIViewController where UIPageViewController is added as child VC.
class ViewController: UIViewController {
    var pageNavigationController: UIPageViewController! 

    private var lastPosition: CGFloat
    private var nextIndex: Int
    var currentIndex: Int     

    // rest of UI's setups  
}
  1. Set ViewController as delegate of UIPageViewController:
extension ViewController: UIPageViewControllerDataSource {

    func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {
        guard
            let currentVisibleViewController = pageViewController.viewControllers?.first,
            let nextIndex = pageViewControllers.firstIndex(of: currentVisibleViewController)
        else {
            return
        }

        self.nextIndex = nextIndex
    }

    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        if completed, let currentVisibleViewController = pageViewController.viewControllers?.first, let newIndex = pageViewControllers.firstIndex(of: currentVisibleViewController) {
            self.currentIndex = newIndex
        }

        self.nextIndex = self.currentIndex
    }
}
  1. Set ViewController as datasource of UIPageController:
extension ViewController: UIPageViewControllerDataSource {

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        // provide next VC
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        // provide prev VC
    }

    // IMPORTANT: that's the key why it works, don't forget to add it
    func presentationIndex(for pageViewController: UIPageViewController) -> Int {
        return currentIndex
    }
}
  1. "Disable" bouncing by setting ViewController as delegate of UIPageViewController's UIScrollView:
// MARK: - UIScrollViewDelegate (disable bouncing for UIPageViewController)
extension BasePaginationVC: UIScrollViewDelegate {

    func attachScrollViewDelegate() {
        for subview in pageNavigationController.view.subviews {
            if let scrollView = subview as? UIScrollView {
                scrollView.delegate = self
                lastPosition = scrollView.contentOffset.x
                break
            }
        }
    }

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        switch UIView.userInterfaceLayoutDirection(for: view.semanticContentAttribute) {
        case .leftToRight:
            if nextIndex > currentIndex {
                if scrollView.contentOffset.x < (lastPosition - (0.9 * scrollView.bounds.size.width)) {
                    currentIndex = nextIndex
                }
            } else {
                if scrollView.contentOffset.x > (lastPosition + (0.9 * scrollView.bounds.size.width)) {
                    currentIndex = nextIndex
                }
            }

            if currentIndex == 0 && scrollView.contentOffset.x < scrollView.bounds.size.width {
                scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
            } else if currentIndex == pageViewControllers.count - 1 && scrollView.contentOffset.x > scrollView.bounds.size.width {
                scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
            }
        case .rightToLeft:
            if nextIndex > currentIndex {
                if scrollView.contentOffset.x > (lastPosition + (0.9 * scrollView.bounds.size.width)) {
                    currentIndex = nextIndex
                }
            } else {
                if scrollView.contentOffset.x < (lastPosition - (0.9 * scrollView.bounds.size.width)) {
                    currentIndex = nextIndex
                }
            }

            if currentIndex == pageViewControllers.count - 1 && scrollView.contentOffset.x < scrollView.bounds.size.width {
                scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
            } else if currentIndex == 0 && scrollView.contentOffset.x > scrollView.bounds.size.width {
                scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
            }
        @unknown default:
            fatalError("unknown default")
        }

        lastPosition = scrollView.contentOffset.x
    }

    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        switch UIView.userInterfaceLayoutDirection(for: view.semanticContentAttribute) {
        case .leftToRight:
            if currentIndex == 0 && scrollView.contentOffset.x <= scrollView.bounds.size.width {
                targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
            } else if currentIndex == pageViewControllers.count - 1 && scrollView.contentOffset.x >= scrollView.bounds.size.width {
                targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
            }
        case .rightToLeft:
            if currentIndex == pageViewControllers.count - 1 && scrollView.contentOffset.x <= scrollView.bounds.size.width {
                targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
            } else if currentIndex == 0 && scrollView.contentOffset.x >= scrollView.bounds.size.width {
                targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
            }
        @unknown default:
            fatalError("unknown default")
        }
    }
}


来源：https://stackoverflow.com/questions/21798218/disable-uipageviewcontroller-bounce

标签
ios
iphone
objective-c
uipageviewcontroller
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