Recently I've got stuck in a bug of pushing UIViewController to UINavigationViewController, and I've found the solution for it.
Bug scenario:
it doesn't matter how you push the UIViewController (by segue, using pushViewController, ..). In RootViewController of your NavigationViewController, try to use swipe back gesture! (nothing should happen), then try to push a ViewController into your NavigationViewController by tapping an element. => App Freezes! Here, if you capture the screen by XCode, you will find that the current visible screen is the next screen!! (but it's not!), Cpu usage and any other things are normal. you can get out of App Freezing by just another swipe back gesture!
Here is the solution:
In your BaseNavigationViewController (which extends UINavigationViewController) insert these codes (especially when you're using UITabbarNavigationViewController)
- (void)navigationController:(UINavigationController *)navigationController
didShowViewController:(UIViewController *)viewController
animated:(BOOL)animate {
if ([self respondsToSelector:#selector(interactivePopGestureRecognizer)]) {
if (self.viewControllers.count > 1) {
self.interactivePopGestureRecognizer.delegate = self;
self.interactivePopGestureRecognizer.enabled = YES;
} else {
self.interactivePopGestureRecognizer.delegate = nil;
self.interactivePopGestureRecognizer.enabled = NO;
}
}
}
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
if ([self respondsToSelector:#selector(interactivePopGestureRecognizer)]) {
return self.viewControllers.count > 1;
}
return NO;
}
Do not forget to write these codes too:
in viewDidLoad of BaseNavigationViewController:
self.delegate = self;
and your BaseNavigationViewController must use these two protocols:
UINavigationControllerDelegate, UIGestureRecognizerDelegate
Related
There's a behavior in the Line messenger app (the de facto messenger app in Japan) that I'm trying to emulate.
Basically, they have a modal view controller with a scroll view inside. When the scroll action reaches the top of its content, the view controller seamlessly switches to an interactive dismissal animation. Also, when the gesture returns the view to the top of the screen, control is returned to the scroll view.
Here's a gif of how it looks.
For the life of me, I can't figure out how they did it. I've tried a few different methods, but they've all failed, and I'm out of ideas. Can anyone point me in the right direction?
EDIT2
To clarify, the behavior that I want to emulate isn't just simply dragging the window down. I can do that, no problem.
I want to know how the same scroll gesture (without lifting the finger) triggers the dismissal transition and then transfers control back to the scroll view after the view has been dragged back to the original position.
This is the part that I can't figure out.
End EDIT2
EDIT1
Here's what I have so far. I was able to use the scroll view delegate methods to add a target-selector that handles the regular dismissal animation, but it still doesn't work as expected.
I create a UIViewController with a UIWebView as a property. Then I put it in a UINavigationController, which is presented modally.
The navigation controller uses animation/transition controllers for the regular interactive dismissal (which can be done by gesturing over the navigation bar).
From here, everything works fine, but the dismissal can't be triggered from the scroll view.
NavigationController.h
#interface NavigationController : UINavigationController <UIViewControllerTransitioningDelegate>
#property (nonatomic, strong) UIPanGestureRecognizer *gestureRecog;
- (void)handleGesture:(UIPanGestureRecognizer*)gestureRecognizer;
#end
NavigationController.m
#import "NavigationController.h"
#import "AnimationController.h"
#import "TransitionController.h"
#implementation NavigationController {
AnimationController *_animator;
TransitionController *_interactor;
}
- (instancetype)init {
self = [super init];
self.transitioningDelegate = self;
_animator = [[AnimationController alloc] init];
_interactor = [[TransitionController alloc] init];
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Set the gesture recognizer
self.gestureRecog = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handleGesture:)];
[self.view addGestureRecognizer:_gestureRecog];
}
- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator {
if (animator == _animator && _interactor.hasStarted) {
return _interactor;
}
return nil;
}
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed {
if (dismissed == self || [self.viewControllers indexOfObject:dismissed] != NSNotFound) {
return _animator;
}
return nil;
}
- (void)handleGesture:(UIPanGestureRecognizer *)gestureRecog {
CGFloat threshold = 0.3f;
CGPoint translation = [gestureRecog translationInView:self.view];
CGFloat verticalMovement = translation.y / self.view.bounds.size.height;
CGFloat downwardMovement = fmaxf(verticalMovement, 0.0f);
CGFloat downwardMovementPercent = fminf(downwardMovement, 1.0f);
switch (gestureRecog.state) {
case UIGestureRecognizerStateBegan: {
_interactor.hasStarted = YES;
[self dismissViewControllerAnimated:YES completion:nil];
break;
}
case UIGestureRecognizerStateChanged: {
if (!_interactor.hasStarted) {
_interactor.hasStarted = YES;
[self dismissViewControllerAnimated:YES completion:nil];
}
_interactor.shouldFinish = downwardMovementPercent > threshold;
[_interactor updateInteractiveTransition:downwardMovementPercent];
break;
}
case UIGestureRecognizerStateCancelled: {
_interactor.hasStarted = NO;
[_interactor cancelInteractiveTransition];
break;
}
case UIGestureRecognizerStateEnded: {
_interactor.hasStarted = NO;
if (_interactor.shouldFinish) {
[_interactor finishInteractiveTransition];
} else {
[_interactor cancelInteractiveTransition];
}
break;
}
default: {
break;
}
}
}
#end
Now, I have to get that gesture handling to trigger when the scroll view has reached the top. So, here's what I did in the view controller.
WebViewController.m
#import "WebViewController.h"
#import "NavigationController.h"
#interface WebViewController ()
#property (weak, nonatomic) IBOutlet UIWebView *webView;
#end
#implementation WebViewController {
BOOL _isHandlingPan;
CGPoint _topContentOffset;
}
- (void)viewDidLoad {
[super viewDidLoad];
[self.webView.scrollView setDelegate:self];
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if ((scrollView.panGestureRecognizer.state == UIGestureRecognizerStateBegan ||
scrollView.panGestureRecognizer.state == UIGestureRecognizerStateChanged) &&
! _isHandlingPan &&
scrollView.contentOffset.y < self.navigationController.navigationBar.translucent ? -64.0f : 0) {
NSLog(#"Adding scroll target");
_topContentOffset = CGPointMake(scrollView.contentOffset.x, self.navigationController.navigationBar.translucent ? -64.0f : 0);
_isHandlingPan = YES;
[scrollView.panGestureRecognizer addTarget:self action:#selector(handleGesture:)];
}
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
NSLog(#"Did End Dragging");
if (_isHandlingPan) {
NSLog(#"Removing action");
_isHandlingPan = NO;
[scrollView.panGestureRecognizer removeTarget:self action:#selector(handleGesture:)];
}
}
- (void)handleGesture:(UIPanGestureRecognizer*)gestureRecognizer {
[(NavigationController*)self.navigationController handleGesture:gestureRecognizer];
}
This still doesn't work quite right. Even during the dismissal animation, the scroll view is still scrolling with the gesture.
End EDIT1
That is a custom interactive transition.
First, you need set transitioningDelegate of UIViewController
id<UIViewControllerTransitioningDelegate> transitioningDelegate;
Then implment these two method to
//Asks your delegate for the transition animator object to use when dismissing a view controller.
- animationControllerForDismissedController:
//Asks your delegate for the interactive animator object to use when dismissing a view controller.
- interactionControllerForDismissal:
When drag to top, you start the transition, you may use UIPercentDrivenInteractiveTransition to control the progress during scrolling.
You can also refer to the source code of ZFDragableModalTransition
Image of ZFDragableModalTransition
As explained here the solution is quite complex. The person who answered, #trungduc, programmed a little demo published on github doing the sought behaviour. You can find it here.
The easiest way of making this work is to copy the 4 files found in /TestPanel/Presentation/ in the attached github repository, to your project. Then add the PanelAnimationControllerDelegate to your View Controller containing the scroll view (i.e. using the protocol).
Add the following to your View Controller, to satisfy the protocol:
func shouldHandlePanelInteractionGesture() -> Bool {
return (scrollView.contentOffset.y == 0);
}
Add this to deactivate the bouncing effect at the top:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
scrollView.bounces = (scrollView.contentOffset.y > 10);
}
Set scrollView.delegate = self
Before presenting your View Controller containing the scroll view set the following propreties to your View Controller:
ScrollViewController.transitioningDelegate = self.panelTransitioningDelegate
ScrollViewController.modalPresentationStyle = .custom
If you want to change the size of your ScrollViewController, you will need to comment out the override of the frameOfPresentedViewInContainerView in the PanelPresentationController file (one of the 4). Then in the presentationTransitionWillBegin method, you will need to set let frameOfPresentedViewInContainerView = self.frameOfPresentedViewInContainerView.insetBy(dx: 0, dy: 20) with the wanted inset of dx and dy.
Thank you to trungduc for this amazing solution!!
I've been working with the Apple sample code for viewing documents from here:
https://developer.apple.com/library/ios/samplecode/DocInteraction/Listings/ReadMe_txt.html
I have removed all the bits I don't need and got it working pretty much how I would like it to. The problem is I don't want users to have access to the "Actions" menu on the top right of the Document Controller. This appears every time you select a document from the list:
Ideally I would like to remove the button all together, though if I could disable it or disable all the options inside it that would also suffice. I found this question:
Open in + UIDocumentInteractionController : how to filter options in SDK iOS 6 (canPerformActions is deprecated)
But I couldn't figure out how to use the suggestion to disable the options inside the menu. I have uploaded the modified sample code here:
http://plasma.servebeer.com/DocSampleCode.zip
One final note is this will not be going on the App Store it is for private, personal use, so if there is an unofficial way then I would be interested in knowing that too.
Any help would be greatly appreciated, thanks in advance.
Plasma
Use UINavigationControllerDelegate
#interface DITableViewController () <UIDocumentInteractionControllerDelegate, UINavigationControllerDelegate>
Assign navigationController delegate to self
- (void)viewDidLoad {
[super viewDidLoad];
self.navigationController.delegate = self;
}
Change documentInteractionControllerViewControllerForPreview
- (UIViewController *)documentInteractionControllerViewControllerForPreview:(UIDocumentInteractionController *)interactionController {
return self.navigationController;
}
Add this UINavigationControllerDelegate method
// Called when the navigation controller shows a new top view controller via a push, pop or setting of the view controller stack.
- (void)navigationController:(UINavigationController*)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
if ([viewController isKindOfClass:[QLPreviewController class]]) {
viewController.navigationItem.rightBarButtonItem = nil;
}
}
Update for MP4 files
In MP4 files the action button is on the UIToolbar
- (void)navigationController:(UINavigationController*)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
if ([viewController isKindOfClass:[QLPreviewController class]]) {
viewController.navigationItem.rightBarButtonItem.customView = [[UIView alloc] init];
UIBarButtonItem *item = viewController.toolbarItems.firstObject;
item.customView = [[UIView alloc] init];
}
}
N.B. This might not work in future versions of iOS
After creating QLPreviewController class you would need to set rightBarButtonItem to nil. Code snippet:
QLPreviewController *previewController = [[QLPreviewController alloc] init];
previewController.navigationItem.rightBarButtonItem = nil;
I did download project and after execution "Action" button was shown not in the top navigation item, but in the toolbar. Then in this case you would need to subclass QLPreviewController and override viewWillAppear as shown below.
#implementation ExViewController
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
NSMutableArray *a = [NSMutableArray arrayWithArray:#[]];
for (NSUInteger i = 0; i < self.toolbarItems.count; i++) {
if (i == 0) {
continue;
}
[a addObject:self.toolbarItems[i]];
}
}
#end
If you want to hide button the give answers will not work for iOS 10.0 and above in Swift language. You can use WKWebView. Hope it will save your time.
Sorry for the long-winded explination, but this question - or something similar - has been asked a few times and I havent found a satisfactory answer. I am writing an iPad app in iOS 8 that implements UISplitViewController. Recently I have been attempting to get it to work on the iPhone. It transferred over pretty well, everything collapses automatically and a back button is included in the left side of my nav. bar.
My problem is that I want to keep the back button functionality to pop one view off the stack, but also be able to pan back to the primary view even if there are several detail views on top of it. Ideally, I want to be able to overwrite or redirect the interactivePopGestureRecognizer so that the gesture smoothly pans to the primary view (in some cases it can have anywhere from 1 to 4 detail views stacked on top of it). But, I cannot figure out how to do this.
My current solution (code below) is to disable the interactivePopGestureRecognizer in the detail viewcontroller and implement my own ScreenEdgePanGestureRecognizer that, when triggered, executes popToRootViewController. I've subclassed the ScreenEdgePanGestureRecognizer so it treats the screen edge pan as a discrete "swipe" (i.e. once a large enough screen edge swipe is detected - pop everything off the stack so the primary view is visible).
Code in detail view controller to stop interactivePopGestureRecognizer:
-(void)viewWillAppear : (BOOL) animated {
[super viewWillAppear : animated];
// stops navigation controller from responding to the default back swipe gesture
if ([self.navigationController respondsToSelector:#selector(interactivePopGestureRecognizer)]) {
self.navigationController.interactivePopGestureRecognizer.enabled =NO;
self.navigationController.interactivePopGestureRecognizer.delegate = self;
}
}
// Disable the default back swipe gesture tied to automatically included back button
-(BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
if ([gestureRecognizer isEqual:self.navigationController.interactivePopGestureRecognizer]) {
return NO;
} else {
return YES;
}
}
I didn't think it was necessary to include my subclass for the screenEdgePanGestureRecognizer because it has nothing to do with the solution I am asking about here is some pseudocode that shows what my #selector does in the detail viewcontroller:
- (IBAction)leftEdgeSwipe:(ScreenEdgeSwipeGestureRecognizer*)sender {
if (sender.swipeIsValid) {
[(UINavigationController *)self.splitViewController.viewControllers[0]
popToRootViewControllerAnimated:YES];
}
}
I tried to use the continuous pan, but cannot find a way to present the primary view in the background as I am pulling the current view aside to give that clean, smooth panning effect. I am able to make it so I can move the current view around, but there is just a grey background behind it where I would want my primary view to be.
Summation: If there is indeed no way to change the interactivePopGestureRecognizer to always jump to my primary view (ideal solution), then any info on how I can make my own smooth pan back to my primary view would be much appreciated.
So I have been messing around with making a smooth panning gesture subclass. Currently it functions similarly to Apple's back gesture except it jumps all the way back to the root view controller instead of popping one view off the stack. The only problem is that it does not yet show the primary view in the background while panning. I will update the answer once I get that worked out.
Here is the subclass:
#import <UIKit/UIKit.h>
#import <UIKit/UIGestureRecognizerSubclass.h>
#import "ScreenEdgeSwipeGestureRecognizer.h"
#interface ScreenEdgeSwipeGestureRecognizer ()
#property (nonatomic) UINavigationController* navController;
#end
#implementation ScreenEdgeSwipeGestureRecognizer{
CGPoint _screenCenter;
CGPoint _cumulativePanDistance;
}
- (id)initWithNavigationController:(UINavigationController*)navController {
self = [super initWithTarget:self action:#selector(leftEdgePan:)];
_screenCenter = CGPointZero;
_cumulativePanDistance = CGPointZero;
self.edges = UIRectEdgeLeft;
self.navController = navController;
return self;
}
- (IBAction)leftEdgePan:(ScreenEdgeSwipeGestureRecognizer*)sender {
assert(sender == self);
switch (self.state) {
case UIGestureRecognizerStateBegan:
[self initializePositions];
break;
case UIGestureRecognizerStateChanged:
[self updatePositions];
break;
case UIGestureRecognizerStateEnded:
[self animateViewBasedOnCurrentLocation];
break;
case UIGestureRecognizerStateCancelled:
[self animateViewToCenter];
break;
default:
break;
}
// Reset velocity of the pan so current velocity does not compound with velocity of next cycle
[sender setTranslation:CGPointMake(0, 0) inView:sender.view];
}
- (void)initializePositions {
_screenCenter = self.view.center;
_cumulativePanDistance = CGPointZero;
}
- (void)updatePositions {
// Track position of user touch event
CGPoint deltaSinceLastCycle = [self translationInView:self.view];
// View center = view center at last cycle + distance moved by user touch since last cycle
self.view.center=CGPointMake((self.view.center.x + deltaSinceLastCycle.x), self.view.center.y+ 0);
// Update the total positive distance traveled by the user touch event.
_cumulativePanDistance.x = _cumulativePanDistance.x + deltaSinceLastCycle.x;
}
- (void)animateViewBasedOnCurrentLocation {
if (_cumulativePanDistance.x >= (_screenCenter.x - 50)){
[self reset];
[_navController popToRootViewControllerAnimated:YES];
}else{
[self animateViewToCenter];
[self reset];
}
}
- (void)animateViewToCenter {
[UIView animateWithDuration:0.25 animations:^{self.view.center = self->_screenCenter;}];
}
- (void)reset {
[super reset];
_cumulativePanDistance = CGPointZero;
self.state = UIGestureRecognizerStatePossible;
}
#end
Here is how I instantiate the recognizer in my view controller:
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
// Initialize the screen edge pan gesture recognizer.
_masterNavigationController = self.splitViewController.viewControllers[0];
ScreenEdgePanGestureRecognizer* edgePanRecognizer = [[ScreenEdgeSwipeGestureRecognizer alloc] initWithNavigationController:_masterNavigationController];
// Add recognizer to view this controller is bound to.
[self.view addGestureRecognizer:_edgePanRecognizer];
}
I've built a custom UITabBarController with Storyboards/Segues and UIViewController containment. Here is a link to it: https://github.com/mhaddl/MHCustomTabBarController
The UIViewControllers which will be presented by the Container are stored in a NSMutableDictionary (keys are the segues' identifiers). Everything is working fine until the point is reached where I come back to a earlier presented ViewController. At this moment "dealloc" gets called on this ViewController before it is presented.
How can I prevent "dealloc" from getting called so it can be used to unsubscribe from Notifications, and nil delegates.
MHCustomTabBarController:
#implementation MHCustomTabBarController {
NSMutableDictionary *_viewControllersByIdentifier;
}
- (void)viewDidLoad {
[super viewDidLoad];
_viewControllersByIdentifier = [NSMutableDictionary dictionary];
}
-(void) viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if (self.childViewControllers.count < 1) {
[self performSegueWithIdentifier:#"viewController1" sender:[self.buttons objectAtIndex:0]];
}
}
- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
self.destinationViewController.view.frame = self.container.bounds;
}
#pragma mark - Segue
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if (![segue isKindOfClass:[MHTabBarSegue class]]) {
[super prepareForSegue:segue sender:sender];
return;
}
self.oldViewController = self.destinationViewController;
//if view controller isn't already contained in the viewControllers-Dictionary
if (![_viewControllersByIdentifier objectForKey:segue.identifier]) {
[_viewControllersByIdentifier setObject:segue.destinationViewController forKey:segue.identifier];
}
for (UIButton *aButton in self.buttons) {
[aButton setSelected:NO];
}
UIButton *button = (UIButton *)sender;
[button setSelected:YES];
self.destinationIdentifier = segue.identifier;
self.destinationViewController = [_viewControllersByIdentifier objectForKey:self.destinationIdentifier];
}
- (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender {
if ([self.destinationIdentifier isEqual:identifier]) {
//Dont perform segue, if visible ViewController is already the destination ViewController
return NO;
}
return YES;
}
#pragma mark - Memory Warning
- (void)didReceiveMemoryWarning {
[[_viewControllersByIdentifier allKeys] enumerateObjectsUsingBlock:^(NSString *key, NSUInteger idx, BOOL *stop) {
if (![self.destinationIdentifier isEqualToString:key]) {
[_viewControllersByIdentifier removeObjectForKey:key];
}
}];
}
#end
MHTabBarSegue:
#implementation MHTabBarSegue
- (void) perform {
MHCustomTabBarController *tabBarViewController = (MHCustomTabBarController *)self.sourceViewController;
UIViewController *destinationViewController = (UIViewController *) tabBarViewController.destinationViewController;
//remove old viewController
if (tabBarViewController.oldViewController) {
[tabBarViewController.oldViewController willMoveToParentViewController:nil];
[tabBarViewController.oldViewController.view removeFromSuperview];
[tabBarViewController.oldViewController removeFromParentViewController];
}
destinationViewController.view.frame = tabBarViewController.container.bounds;
[tabBarViewController addChildViewController:destinationViewController];
[tabBarViewController.container addSubview:destinationViewController.view];
[destinationViewController didMoveToParentViewController:tabBarViewController];
}
#end
"At this moment "dealloc" gets called on this ViewController before it is presented." -- no, not really. Dealloc is being called on a controller that never gets on screen, not the one you came from initially or are going back to. The way your segue is set up, and the fact that you keep a reference to your controllers in the dictionary, means that they never get deallocated. Segues (other than unwinds) ALWAYS instantiate new view controllers, so what's happening is that a new instance of, say VC1 is created when you click on the first tab (and a segue is triggered), but you never do anything with that controller (which would be self.destinationViewController in the custom segue class) so it's deallocated as soon as the perform method exits.
Depending on where you setup any delegates or notification observers, this might not be a problem -- this controller that's created, and then immediately deallocated never has its viewDidLoad method called, so if you do those things in viewDidLoad, they won't ever happen for this transient view controller.
If you don't want this to happen, then you need to make your transitions in code without using segues.
I have a really interesting issue with UIPageViewController.
My project is set up very similarly to the example Page Based Application template.
Every now and then (but reproducible to a certain extent) a certain pan gesture will call out to -(UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController.
I return the viewcontroller for the next page, but a page flip animation is never ran and my delegate method is never called.
Here is the code for viewControllerAfterViewController
-(UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
PageDisplayViewController *vc = (PageDisplayViewController *)viewController;
NSUInteger index = [self.pageFetchController.fetchedObjects indexOfObject:vc.page];
if(index == (self.pageFetchController.fetchedObjects.count - 1)) return nil;
return [self getViewControllerForIndex:(++index)];
}
Here is the getViewControllerForIndex:
-(PageDisplayViewController *)getViewControllerForIndex:(NSUInteger)index
{
PageDisplayViewController *newVC = [self.storyboard instantiateViewControllerWithIdentifier:#"PageDisplayController"];
newVC.page = [self.pageFetchController.fetchedObjects objectAtIndex:(index)];
newVC.view.frame = CGRectMake(0, 0, 1024, 604);
NSLog(#"%i", index);
if(index == 0)
{
//We're moving to the first, animate the back button to be hidden.
[UIView animateWithDuration:0.5 animations:^
{
self.backButton.alpha = 0.f;
} completion:^(BOOL finished){
self.backButton.hidden = YES;
}];
}
else if(index == (self.pageFetchController.fetchedObjects.count - 1))
{
[UIView animateWithDuration:0.5 animations:^{
self.nextButton.alpha = 0.f;
} completion:^(BOOL finished){
self.nextButton.hidden = YES;
}];
}
else
{
BOOL eitherIsHidden = self.nextButton.hidden || self.backButton.hidden;
if(eitherIsHidden)
{
[UIView animateWithDuration:0.5 animations:^{
if(self.nextButton.hidden)
{
self.nextButton.hidden = NO;
self.nextButton.alpha = 1.f;
}
if(self.backButton.hidden)
{
self.backButton.hidden = NO;
self.backButton.alpha = 1.f;
}
}];
}
}
return newVC;
}
Basically, I create the view controller, set it's data object, then fade a next/back button out depending on the index.
Delegate method
-(void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed
{
PageDisplayViewController *vc = [previousViewControllers lastObject];
NSUInteger index = [self.pageFetchController.fetchedObjects indexOfObject:vc.page];
if (!completed)
{
[self.pagePreviewView setCurrentIndex:index];
NSLog(#"Animation Did not complete, reverting pagepreview");
}
else
{
PageDisplayViewController *curr = [pageViewController.viewControllers lastObject];
NSUInteger i = [self.pageFetchController.fetchedObjects indexOfObject:curr.page];
[self.pagePreviewView setCurrentIndex:i];
NSLog(#"Animation compeleted, updating pagepreview. Index: %u", i);
}
}
I only noticed this issue because randomly, my back button would reappear on screen. After tossing some NSLog() statements in there, I notice that my dataSource method gets called for an index of 1, but no animation ever plays or delegate gets called. Whats even scarier, is that if I try to pan the next page, index 1 gets called for AGAIN.
I fear this may be a bug with the UIPageViewController.
Since I was still receiving mysterious crashes with the implementation in my first answer, I kept searching for a "good enough" solution which depends less on personal assumptions about the page view controller's (PVC) underlying behavior. Here is what I managed to come up with.
My former approach was kind of intrusive and was more of a workaround than an acceptable solution. Instead of fighting the PVC to force it to do what I thought it was supposed to do, it seems that it's better accept the facts that:
the pageViewController:viewControllerBeforeViewController: and pageViewController:viewControllerAfterViewController: methods can be called an arbitrary number of times by UIKit, and
there is absolutely no guarantee that either of these correspond to a paging animation, nor that they will be followed by a call to pageViewController:didFinishAnimating:previousViewControllers:transitionCompleted:
That means we cannot use the before/after methods as "animation-begin" (note, however, that didFinishAnimating still serves as "animation-end" event). So how do we know an animation has indeed started?
Depending on our needs, we may be interested in the following events:
the user begins fiddling with the page:
A good indicator for this is the before/after callbacks, or more precisely the first of them.
first visual feedback of the page turning gesture:
We can use KVO on the state property of the tap and pan gesture recognizers of the PVC. When a UIGestureRecognizerStateBegan value is observed for panning, we can be pretty sure that visual feedback will follow.
the user finishes dragging the page around by releasing the touch:
Again, KVO. When the UIGestureRecognizerStateRecognized value is reported either for panning or tapping, it is when the PVC is actually going to turn the page, so this may be used as "animation-begin".
UIKit starts the paging animation:
I have no idea how to get a direct feedback for this.
UIKit concludes the paging animation:
Piece of cake, just listen to pageViewController:didFinishAnimating:previousViewControllers:transitionCompleted:.
For KVO, just grab the gesture recognizers of the PVC as below:
#interface MyClass () <UIGestureRecognizerDelegate>
{
UIPanGestureRecognizer* pvcPanGestureRecognizer;
UITapGestureRecognizer* pvcTapGestureRecognizer;
}
...
for ( UIGestureRecognizer* recognizer in pageViewController.gestureRecognizers )
{
if ( [recognizer isKindOfClass:[UIPanGestureRecognizer class]] )
{
pvcPanGestureRecognizer = (UIPanGestureRecognizer*)recognizer;
}
else if ( [recognizer isKindOfClass:[UITapGestureRecognizer class]] )
{
pvcTapGestureRecognizer = (UITapGestureRecognizer*)recognizer;
}
}
Then register your class as observer for the state property:
[pvcPanGestureRecognizer addObserver:self
forKeyPath:#"state"
options:NSKeyValueObservingOptionNew
context:NULL];
[pvcTapGestureRecognizer addObserver:self
forKeyPath:#"state"
options:NSKeyValueObservingOptionNew
context:NULL];
And implement the usual callback:
- (void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context
{
if ( [keyPath isEqualToString:#"state"] && (object == pvcPanGestureRecognizer || object == pvcTapGestureRecognizer) )
{
UIGestureRecognizerState state = [[change objectForKey:NSKeyValueChangeNewKey] intValue];
switch (state)
{
case UIGestureRecognizerStateBegan:
// trigger for visual feedback
break;
case UIGestureRecognizerStateRecognized:
// trigger for animation-begin
break;
// ...
}
}
}
When you are done, don't forget to unsubscribe from those notifications, otherwise you may get leaks and strange crashes in your app:
[pvcPanGestureRecognizer removeObserver:self
forKeyPath:#"state"];
[pvcTapGestureRecognizer removeObserver:self
forKeyPath:#"state"];
That's all folks!
Please look at my other answer in the first place, this one has serious flaws but I'm leaving it here as it might still help someone.
First off, a disclaimer: The following solution is a HACK. It does work in the environment I tested but there is no guarantee that it works in yours nor that it won't be broken by the next update. So proceed with care.
TL;DR: grab the UIPanGestureRecognizer of the UIPageViewController and hijack its delegate calls but keep forwarding them to the original target.
Longer version:
My findings on the issue: the UIPageViewController shipped in iOS 6 is different in behavior to the one in iOS 5 in that it may call the pageViewController:viewControllerBeforeViewController: on its datasource even if there is no page turning going on in any sense (read: no tap, swipe, or valid direction-matching panning has been recognized). This, of course, breaks our former assumption that the before/after calls are equivalent to an "animation begin" trigger and are consistently followed by a pageViewController:didFinishAnimating:previousViewControllers:transitionCompleted: call to the delegate. (Eventually this is a bold assumption to make but I guess I was not alone with that.)
I found out that the extra calls to the datasource are likely to happen when the default UIPanGestureRecognizer on the page view controller starts to recognize a pan gesture that in the end doesn't match the direction of the controller (e.g. vertical panning in a horizontally paging PVC). Interestingly enough, in my environment it was always the "before" method which got hit, never the "after". Others suggested interfereing with the gesture recognizer's delegate but that didn't work for me the way it was described there so I kept experimenting.
Finally I found a workaround. First we grab the pan gesture recognizer of the page view controller:
#interface MyClass () <UIGestureRecognizerDelegate>
{
UIPanGestureRecognizer* pvcPanGestureRecognizer;
id<UIGestureRecognizerDelegate> pvcPanGestureRecognizerDelegate;
}
...
for ( UIGestureRecognizer* recognizer in pageViewController.gestureRecognizers )
{
if ( [recognizer isKindOfClass:[UIPanGestureRecognizer class]] )
{
pvcPanGestureRecognizer = (UIPanGestureRecognizer*)recognizer;
pvcPanGestureRecognizerDelegate = pvcPanGestureRecognizer.delegate;
pvcPanGestureRecognizer.delegate = self;
break;
}
}
Then we implement the UIGestureRecognizerDelegate protocol in our class:
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
if ( gestureRecognizer == pvcPanGestureRecognizer &&
[pvcPanGestureRecognizerDelegate respondsToSelector:#selector(gestureRecognizer:shouldReceiveTouch:)] )
{
return [pvcPanGestureRecognizerDelegate gestureRecognizer:gestureRecognizer
shouldReceiveTouch:touch];
}
return YES;
}
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
if ( gestureRecognizer == pvcPanGestureRecognizer &&
[pvcPanGestureRecognizerDelegate respondsToSelector:#selector(gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:)] )
{
return [pvcPanGestureRecognizerDelegate gestureRecognizer:gestureRecognizer
shouldRecognizeSimultaneouslyWithGestureRecognizer:otherGestureRecognizer];
}
return NO;
}
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
if ( gestureRecognizer == pvcPanGestureRecognizer &&
[pvcPanGestureRecognizerDelegate respondsToSelector:#selector(gestureRecognizerShouldBegin:)] )
{
return [pvcPanGestureRecognizerDelegate gestureRecognizerShouldBegin:gestureRecognizer];
}
return YES;
}
Apparently, the methods don't do anything sensible, they just forward the invocations to the original delegate (making sure that that actually implements them). Still, this forwarding seems to be sufficient for the PVC to behave and not call the datasource when there is no need to.
This workaround fixed the issue for me on devices running iOS 6. Code which was compiled with the iOS 6 SDK but with a deployment target of iOS 5 had already run flawlessly on 5.x devices, so the fix is not necessary there but according to my tests it doesn't do any harm either.
Hope someone finds this useful.
I have tried your solution and it came almost working, but still with some issues. The best solution came with adding method
- (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers
which is available starting from iOS 6 and it is required for it. If not to implement it, issues may occur with those gestures. Implementing it helped to solve major part of issues.
try this...
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
for (UIGestureRecognizer *gr in pageViewController.gestureRecognizers) {
if([gr isKindOfClass:[UIPanGestureRecognizer class]])
{
UIPanGestureRecognizer *pgr = (UIPanGestureRecognizer*)gr;
CGPoint velocity = [pgr velocityInView:pageViewController.view];
BOOL verticalSwipe = fabs(velocity.y) > fabs(velocity.x);
if(verticalSwipe)
return nil;
}
}
....
}