UIPageViewController not keeping track of page index - ios

I've been struggling all weekend with this problem and have spent a long time googling to find the solution without any success.
My use case is pretty simple and I can't believe how difficult it is to make such a trivial behaviour work correctly.
My app is a simple paginated flow where users swipe left or right to see the next or previous page. I have a UIPageViewController and each page contains a UITableView. I have had problems trying to keep track of the page index inside the viewControllerAfterViewController and viewControllerBeforeViewController functions for the reasons explained here: PageViewController delegate functions called twice
I've tried following all the suggested workarounds for this problem (keeping track of the index inside willTransitionToViewControllers and didFinishAnimating) but this doesn't solve my problem as the viewController*ViewController functions must still return a viewController and since they are initially called twice, the first returned viewController seems to be the one that gets used and the second pass through doesn't seem to have any affect.
Although I've seen many questions and blogs about this problem, I haven't seen a single example that shows how to consistently return the correct viewController from the viewController*ViewController functions and would be massively grateful for an example. The main issue I can't see a solution to is how to determine the next index inside willTransitionToViewControllers if I only have a single viewController whose content is dynamically updated on page load. It seems like a chicken and egg problem to me; I need to figure out what content to update the page with, but to do that I need to know what the index of the page is (which is part of the content).
Edit
Here is a distilled version of the affected code:
- (void)viewDidLoad {
[super viewDidLoad];
_pageViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"PageViewController"];
_pageViewController.dataSource = self;
_pageViewController.delegate = self;
[self.view addSubview:_pageViewController.view];
PageContentViewController *startingPage = [self viewControllerAtIndex:0];
NSArray *viewControllers = #[startingPage];
[_pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {
// Don't do any index calculations as the result is inconsistent
return [self viewControllerAtIndex:nextIndex];
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController {
// Don't do any index calculations as the result is inconsistent
return [self viewControllerAtIndex:nextIndex];
}
- (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers {
// This value never changes because the global _pageViewContentController hasn't been updated yet
nextIndex = [((PageContentViewController *)pendingViewControllers[0]) pageIndex];
}
- (PageContentViewController *)viewControllerAtIndex:(NSUInteger)index {
_pageContentViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"PageContentViewController"];
_pageContentViewController.pageIndex = index;
_pageContentViewController.title = index;
return _pageContentViewController;
}
I've debugged the order in which these functions get called and would expect the global _pageViewContentController to be populated with the correct data after the page has transitioned.
Edit 2
To give some more detail on my problem; each of my pages contains a title and a table of web links. Clicking on a link opens a WebViewController to display the selected web page. With Yunus' solution below, everything displays correctly (the title and links appear as expected) but the problem comes when clicking on a link as this loads a link from the next page. It seems like the rendering phase of the page happens at the point the data is correct, but it then reinitialises the page content controller with incorrect data after rendering has finished which is why the actual link data is wrong (even though the rendered data is good).

Let's keep all the related contentViewControllers in an array
self.contentViewControllers = [NSMutableArray new];
for(int i=0; i< MAX_INDEX; i++) {
[self.contentViewControllers addObject:[self viewControllerAtIndex:0]];
}
Then what we need to do is to decide which view controller we should show on after and before methods
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerBeforeViewController:(UIViewController *)viewController
{
for(int i=0;i<self.contentViewControllers.count ;i++)
{
if(viewController == [self.contentViewControllers objectAtIndex:i])
{
if(i-1 >= 0)
{
return [self.contentViewControllers objectAtIndex:i-1];
}
}
}
return nil;
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerAfterViewController:(UIViewController *)viewController
{
for(int i=0;i<self.contentViewControllers.count ;i++)
{
if(viewController == [self.contentViewControllers objectAtIndex:i])
{
if(i+1 < self.contentViewControllers.count)
{
return [self.contentViewControllers objectAtIndex:i+1];
}
}
}
return nil;
}
Then in the transition method
- (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers
{
UIViewController* viewController = [pendingViewControllers objectAtIndex:0];
NSInteger nextIndex = [self.contentViewControllers indexOfObject:viewController];
[self.pageControl setCurrentPage:nextIndex];
}

Related

How do I create variable number of ViewControllers within a PageViewController?

I have a UIPageViewController in a container that is supposed to show, at minimum, three pages; at maximum, six. The number of pages would be determined by the user before the PageViewController appears.
For a bigger picture, I'm trying to create a project management application that allows for an agile ticket creating and management system. The PageVC is supposed to flip through 3 to 6 columns depending on how many the user wants to go along with that project. As an example, if it's a simple project, they can just have three columns named: "Unassigned", "Assigned", and "Complete". More complex projects could, for example, have 5 columns, named: "Backlog", "Issues", "In Progress", "Review", "Done". Each one of those columns would have its own ViewController within the PageVC.
This is what my data model looks like, to get an idea of where I get the number of columns from (Project attribute named: "projectColumnCount"):-
you can use following ObjectiveC concept in Swift.
It is Advisable to create a content view controller initially and then to use Pageviewcontroller Delegate Methods to create other controllers.
you can check following delegate Methods of Pageviewcontroller for same
Delegate Methods for Pageviewcontroller are as below.
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
NSUInteger index = ((PageContentViewController*) viewController).pageIndex;
if ((index == 0) || (index == NSNotFound)) {
return nil;
} index--;
return [self viewControllerAtIndex:index];
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
NSUInteger index = ((PageContentViewController*) viewController).pageIndex;
if (index == NSNotFound)
{
return nil;
}
index++;
if (index == [arrPage count]) {
return nil;
}
return [self viewControllerAtIndex:index];
}
you can use below method to create instance of ContentVC
- (PageContentViewController *)viewControllerAtIndex:(NSUInteger)index
{
if (([arrPage count] == 0) || (index >= [arrPage
count])) {
return nil;
}
// Create a new view controller and pass suitable data.
pageContentViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"PageContentViewController"];
pageContentViewController.delagate = self;
pageContentViewController.pageIndex = index;
pageContentViewController.collselectedType = selectedType;
return pageContentViewController;
}
you can also Create Array of contentVC and can set that in Pageviewcontroller but it will consume more memory
you can set view conteollers array as below.
[self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];

How to conditionally go to the next page in pageViewController?

I am using pageViewController in my App. I have 9 pages which are created dymanically and each page have 1 question which have 4 multiple choice answers. Each option have custom UIButton with image and its "BlankedCheckBox" when the option is not selected and "MakredCheckBox" when its selected. Right now I can go to next page even if any of the available answer is not selected. I want to go to the next page only if user has selected one of the available option. The transition style of my pageViewController is scroll.
It seems to me like I have to add something in following method. Any help would be greatly appreciated, thanks.
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController {
NSUInteger index = ((PageContentViewController *) viewController).pageIndex;
if (index == NSNotFound) {
return nil;
}
index ++;
if (index == [self.questionTitles count]) {
return nil;
}
return [self viewControllerAtIndex:index];
}
You should not implement the dataSource methods. If you do the user can scroll using a gesture.
To achieve the behavior you want, set the page in code in the IBAction of the control:
- (IBAction)nextPage {
[self setViewControllers:[nextViewController]
direction: UIPageViewControllerNavigationDirectionForward
animated:YES
completion:nil];
}

How should I pass data between UIViewControllers in UIPageViewController and save variables

I am having trouble figuring out how to save/pass data between UIViewControllers in UIPageViewController. My setup is like so:
#pragma mark - UIPageViewControllerDataSource
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
//This is nice and avoids having to use a counter
NSString *vcRestorationID = viewController.restorationIdentifier;
NSUInteger index = [self.controllerRestorationIDs indexOfObject:vcRestorationID];
if (index == 0) {
return nil;
}
return [self viewControllerAtIndex:index - 1];
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
NSString *vcRestorationID = viewController.restorationIdentifier;
NSUInteger index = [self.controllerRestorationIDs indexOfObject:vcRestorationID];
//Don't allow it to go forward if there is one at the end
if (index == self.controllerRestorationIDs.count - 1) {
return nil;
}
return [self viewControllerAtIndex:index + 1];
}
#pragma mark - Private Methods
- (UIViewController *)viewControllerAtIndex:(NSUInteger)index
{
// Only process a valid index request.
if (index >= self.controllerRestorationIDs.count) {
return nil;
}
// Create a new view controller.
//Note this is just an extension of UIViewController with a variable inside. All my view controllers in this must be subclassed off BaseContentViewController
BaseContentViewController *contentViewController = (BaseContentViewController *)[self.storyboard instantiateViewControllerWithIdentifier:self.controllerRestorationIDs[index]];
// Set any data needed by the VC here
contentViewController.rootViewController = self;
return contentViewController;
}
This is in my RootViewController.m (the controller that contains UIPageViewController). What I need to be able to do is so save a variable or data in the current displayed controller when a new one is swiped to. Do I need to use a singleton or something for this?
Try to use NSNotificationCenter class in your *ViewController(s)
NSNotificationCenter will probably be your fastest implementation if you only ever have to pass small pieces of information back and forth and need to do so to multiple destinations simultaneously. If, in the far more likely instance, you need to update information frequently and reference it only when necessary then a singleton would be a much more practical solution.
Singletons are surprisingly easy to use and implement. A quick google search had this walkthrough as the first result. That will show you how to set it up, and using it is very similar to using any other property in a view controller.
It may take a couple extra minutes of work to get running over NSNotificationCenter but it's more extensible, readable, and maintainable.

UIPageViewController programmatically tell what page is showing

is there a way to programmatically tell when a certain page is showing in a pageviewcontroller? For example, I instantiated it as the following:
if (index == 0) {
pageContentViewController = [storyboard instantiateViewControllerWithIdentifier:#"OnCampusTable"];
}
else if (index == 1) {
pageContentViewController = [storyboard instantiateViewControllerWithIdentifier:#"OffCampusTable"];
}
else if (index == 2) {
pageContentViewController = [storyboard instantiateViewControllerWithIdentifier:#"MyEventsTable"];
}
I want to write something where
if (current page is "OnCampusTable") {
method 1
}
else if (current page is "OffCampusTable") {
method 2
}
else if (current page is "MyEventsTable") {
method 3
}
I've tried using the index, but because of the way that the pages load and stuff, it actually doesn't work properly. I was thinking of trying to access the page indicator thing (the little circle things) to get the page number, but I don't know how to do that.
I've seen a few solutions out there that use an array of ViewControllers and do comparisons, but I don't want to keep a bunch of controllers around (I generate them on the fly from my model), so I found a solution that seems to work.
Basically I point a property to the prior and next controllers in the data source before and after methods. In the delegate's didFinishAnimating call I compare the new controller to these properties to see if we moved forward or backward. One caveat is that before and after don't get called if the controller has already been loaded, so I reassign my property based on didFinishAnimating's previousViewController's value.
Note, I only implemented this for the case where one page is displayed.
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {
if (self.pageIndex > 0) {
UIViewController *vc = [self genController:self.trackList[self.pageIndex - 1]];
self.priorVC = vc;
return vc;
} else {
self.priorVC = nil;
return nil;
}
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController {
if (self.pageIndex < self.trackList.count - 1) {
UIViewController *vc = [self genController:self.trackList[self.pageIndex + 1]];
self.nextVC = vc;
return vc;
} else {
self.nextVC = nil;
return nil;
}
}
- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed
{
if (finished && completed) {
if (pageViewController.viewControllers.lastObject == self.priorVC) {
NSLog(#"Back");
self.pageIndex--;
self.nextVC = previousViewControllers.lastObject;
} else if (pageViewController.viewControllers.lastObject == self.nextVC) {
NSLog(#"Forward");
self.pageIndex++;
self.priorVC = previousViewControllers.lastObject;
}
NSLog(#"Page: %ld",self.pageIndex);
}
}
You can use the delegate method pageViewController:didFinishAnimating:previousViewControllers:transitionCompleted: to keep track of the current page and then execute some method depending on the page.

Getting index number slow in UIpageviewController while using custom pageControl

Before closing this question as a duplicate just see I'm facing a serious issue for the past two days.
I'm following UIPageViewController with storyboards tutorial.
I tried to develop my UIPageviewController. I've to show a number of user photos. I don't want to show apagecontrol in bottom so I created a custom page control instead. When I try to set the index to the UIPageControl it's not working properly - getting some delay some times reaching 5th page only its updating so the counts are not proper
This is my datasource:
-(UIViewController*)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
NSUInteger index = ((BMEnlargePhotoPageView*) viewController).pageIndex;
[self.enlargePhotoPageControl setCurrentPage:index];
if((index == 0 ) || (index==NSNotFound)){
return nil;
}
index--;
return [self viewControllerATindex:index];
}
-(UIViewController*)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
NSUInteger index = ((BMEnlargePhotoPageView*) viewController).pageIndex;
[self.enlargePhotoPageControl setCurrentPage:index];
if(index==NSNotFound){
return nil;
}
index++;
if(index==[self.userImages count])
{
return nil;
}
return [self viewControllerATindex:index];
}
- (BMEnlargePhotoPageView*)viewControllerATindex:(NSUInteger)index
{
if(([self.userImages count]==0) || (index >= [self.userImages count])){
}
BMEnlargePhotoPageView *PageContentViewControl = [self.storyboard instantiateViewControllerWithIdentifier:#"EnlargePhoto"];
PageContentViewControl.imageFIle =self.userImages[index];
PageContentViewControl.pageIndex = index;
return PageContentViewControl;
}
My other issue is that I want to find the current visible photos's index ID so that too I can't take properly - it's getting delayed value and is not correct.
Note: when I use animation page scroll everything works well but in scroll animation it's getting delayed but I want to show it as scroll only i tried many SO ansers nothing getting my problem some one guide or am i doing any wrong.
After long frustration week finally found which one good with iOS7 and don mind answering my question bcz no one answered so i supposed to fill the blank space.
In UIPageViewController there is delegate named didFinishAnimating: so in this there is a BOOL function which can identify your page turned completely or partially so using that BOOL you can check that and when you using even animation scroll it will be useful. Your code goes like this
- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed{
if(completed){
COntentViewController *enlarge =[self.pageViewController.viewControllers lastObject];
self.enlargePhotoPageControl.currentPage = enlarge.pageIndex;
}
}
in this last object hold your last transmitted content if you partially scroll page the BOOL will not be get true it will indicate if the page scrolled completely this will help you those who wants to use custom page control. its working for me well how i expected set your pagecontrol index when the page scrolled completely unless the page indicator will not be set. It remains as last page count thx if i did any mistakes pls correct myself or even some good approach.

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