Enhancement request: Limit scroll to 1 index at a time about fspagerview

[JoeSzymanski]

I ran into this problem, also. I'm going to see if there's anything that can be done to fix this.

I've also seen a case where the end position isn't exactly at one of the photo positions, and I think it might be related.

[JoeSzymanski]

Should be fixed with #22

[WenchaoD]

@JoeSzymanski @saldous Thanks for submitting the issue and the pull request. I've been thinking about this issue. Limiting the scrolling index to 1 could be a good performance if the itemSize is the same as the parent (the pager view), not if the itemSize is small. Probably you'll get the idea if you open App Store in your iPhone and try flipping the items fast in home page, or the screenshots in detail page.

[JoeSzymanski]

I didn't think about that specifically, but at the same time, I did make my fix require turning the feature on. The default behavior remains in place without the developer choosing to limit scrolling to one page at a time.

[saldous]

Thanks, agreed, should be optional so developer can decide if they want this behavior or not.

[saldous]

@JoeSzymanski I'm seeing multiple issues with the fix you provided. Doesn't seem to have been done against latest version?

[JoeSzymanski]

It was done against master a few days ago. I just merged the latest changes in and resolved the one conflict. Please check it again.

EDIT - I will have to go back and test against new vertical scrolling feature. I'll looking into that shortly.

[JoeSzymanski]

I'm not sure how easily I'll be able to get this 100% functional. It works well for horizontal mode if the item size approximately matches the screen size. For the quick testing of the vertical case, this is much less likely, and has the problems @WenchaoD was referencing earlier. I don't know what the best way to deal with that is, even though I know I need the basic case for full-screen horizontal paging to be able to make use of the library.

I'm open to suggestions on how to resolve these problems.

[satishVekariya]

@WenchaoD I have idea to limit one item plz refer my below code

var offsetAtBegin:CGPoint?
    public func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if let offset = offsetAtBegin {
            let pageSide:CGFloat = collectionViewLayout.itemSpacing
            if scrollView.contentOffset.x > offset.x + pageSide {
                scrollView.contentOffset.x = offset.x + pageSide
            } else if scrollView.contentOffset.x < offset.x - pageSide {
                scrollView.contentOffset.x = offset.x - pageSide
            }
        }
        if self.numberOfItems > 0 {
            // In case someone is using KVO
            let currentIndex = lround(Double(self.scrollOffset)) % self.numberOfItems
            if (currentIndex != self.currentIndex) {
                self.currentIndex = currentIndex
            }
        }
        guard let function = self.delegate?.pagerViewDidScroll else {
            return
        }
        function(self)
    }
    
    public func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        if let function = self.delegate?.pagerViewWillBeginDragging(_:) {
            function(self)
        }
        if self.automaticSlidingInterval > 0 {
            self.cancelTimer()
        }
        offsetAtBegin = scrollView.contentOffset
    } 

public func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        if let function = self.delegate?.pagerViewDidEndDecelerating {
            function(self)
        }
        offsetAtBegin = nil
    }

[WenchaoD]

Close as already implemented.