UIPageViewController implementation

Question

I'm implementing a page based app.

Basically the pageViewController will be used to show pages of data.

Same format, different data.

Created a ViewController to hold the pageViewController and another viewController which is going to present the data.

I only need one different viewController for the data, I saw this can be a problem.

Normal pagers, like a Android ViewPager, will ask you to return the view you want to show given an index, PageViewController doesn't work like that, it just ask you for the next and the previous viewcontrollers.

I was hoping that storing the index in a property of the content ViewController will do the job... but it wasn't.

It is partially working but..

here is my relevant code:

- (void)viewDidLoad {
    [super viewDidLoad];
    
    page = [[UIPageViewController alloc]initWithTransitionStyle:UIPageViewControllerTransitionStyleScroll navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil];
    
    [page setDelegate:self];
    [page setDataSource:self];
    index = 0;
    
    CampaignContent * content = [[CampaignContent alloc]initWithNibName:@"CampaignContent" bundle:nil];
    [content setTitlestr:@"Index 0"];
    [content setDesc:@"desc1"];
    [content.view setTag:1];
    
    [page setViewControllers:@[content] direction:UIPageViewControllerNavigationDirectionForward animated:TRUE completion:nil];
    
    [page willMoveToParentViewController:self];
    
    [self addChildViewController:page];
    [self.view addSubview:page.view];

    [page didMoveToParentViewController:self];
}

-(UIViewController*)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
    last=false;
    NSLog(@"move right index %i",index);
    CampaignContent * content = [[CampaignContent alloc]initWithNibName:@"CampaignContent" bundle:nil];
    [content setTitlestr:[NSString stringWithFormat:@"Index %i",index+1]];
    [content.view setTag:viewController.view.tag+1];
    return content;
}

- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed
{
    if(completed)
    {
    if([[previousViewControllers objectAtIndex:0] view].tag<index){
        NSLog(@"Left");
        index = index-1;
    }else{
        NSLog(@"Right");
        index = index+1;
    }
        NSLog(@"didFinishAnimating view tag %i",[[previousViewControllers objectAtIndex:0] view].tag,index);
    }
}

-(UIViewController*)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
    last= true;
    NSLog(@"move left index %i",index);
    CampaignContent * content = [[CampaignContent alloc]initWithNibName:@"CampaignContent" bundle:nil];
    [content setTitlestr:[NSString stringWithFormat:@"Index %i",index-1]];
    [content.view setTag:viewController.view.tag-1];
    return content;
}

Just wanting to see the index properly working but instead...

Starting on 0, I swipe to the next page and I see the following in the log

move right index 0
move left index 0
Right
didFinishAnimating view tag 1
move right index 1

Wow such a lot of calls... but index displayed still OK

Again swipe to the next page

Right
didFinishAnimating view tag 2
move right index 2

To this point the index displayed its correct, the problem starts when changing direction.

Swipe to the previous now I see this:

Right
didFinishAnimating view tag 3
move left index 3

Looks like it has failed on didFinishAnimating when determining swipe direction but still index displayed is OK

Again Swipe left

Left
didFinishAnimating view tag 2

Here seems that viewControllerBeforeViewController are not getting called, we have gone from 0->1->2->1->0 right? but index displayed has done 0->1->2->1->2

And if I swipe left again I can see it goes to ->1->0->-1 just like it should.

The same applies going on the other way.

So, I'm thinking that viewControllerBeforeViewController and viewControllerAfterViewController are not reliable and didFinishAnimating can't determine swipe direction alone.

Is there any way I can do this properly or I'm simply doing something bad?

Sorry for my large post, hope someone can help me.

Answer 1

What you can do is use ViewControllerAtIndex method. Inside that method set the contentViewControllers property accordingly based on index.

Then in the viewDidAppear method of contentView Controller you will get the values that you set in the ViewControllerAtIndex method which you can use according to your requirement.