xhist xhist - 4 months ago 78x
iOS Question

Progress of UIPageViewController

I would like to receive updates from the uipageviewcontroller during the page scrolling process. I want to know the transitionProgress in %. (This value should update when the user move the finger in order to get to another page). I'm interested in the animation progress from one page to another, not the progress through the total number of pages.

What I have found so far:

  • There is a class called UICollectionViewTransitionLayout that have the property corresponding to what I am looking for, "transitionProgress". Probably uipageviewcontroller implement this method somehow?

  • I can call the following method on the uipagecontroller but I only get 0 as result!

    CGFloat percentComplete = [self.pageViewController.transitionCoordinator percentComplete];


At last I found out a solution, even if it is probably not the best way to do it:

I first add an observer on the scrollview like this:

// Get Notified at update of scrollview progress
NSArray *views = self.pageViewController.view.subviews;
UIScrollView* sW = [views objectAtIndex:0];
[sW addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew context:NULL];

And when the observer is called:

NSArray *views = self.pageViewController.view.subviews;
UIScrollView* sW = [views objectAtIndex:0];
CGPoint point = sW.contentOffset;

float percentComplete;
//iPhone 5
if([ [ UIScreen mainScreen ] bounds ].size.height == 568){
    percentComplete = fabs(point.x - 568)/568;

} else{
//iphone 4
    percentComplete = fabs(point.x - 480)/480;
NSLog(@"percentComplete: %f", percentComplete);

I'm very happy that I found this :-)