iOS - scrollViewDidEndDecelerating runs for both scrollView and collectionView

问题

I have a VC that contains a collectionView and a scrollView. I put this code to change current page of pageController by scrolling in scrollView :

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {

    let pageNumber = round(scrollView.contentOffset.x / scrollView.frame.size.width)
    self.pageController.currentPage = Int(pageNumber)
}

It works nice for scrollView but the problem is when i even scroll in collectionView it declares and causes unwanted changing in pageController!

What should i do?

回答1:

In addition to the answers posted above, You can make use of the tag property of the view.

Just assign a tag (Int) to your scrollview either in xib or via code.

yourScrollView.tag = 10

And in the scrollview delegate method check for this tag:

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {

    if scrollView.tag == 10 { 
      ///Your scrollview was scrolled
    } else {
      // Collection view was scrolled
    }

}

回答2:

if scrollView == yourScrollView{
    let pageNumber = round(scrollView.contentOffset.x / scrollView.frame.size.width)
    self.pageController.currentPage = Int(pageNumber)
}

check if the instance running the method is actually your scrollView

回答3:

First you have to understand bit detail about UICollectionView. The UICollectionView is subclassed from UIScrollView. That's why its getting called for both the scrolling (Scrolling collection view and scrolling scroll view). You can do like this to differentiate what type of scrolling it is,

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {

    if scrollView == "Your scrollView outlet name" { // Scroll view
        let pageNumber = round(scrollView.contentOffset.x / scrollView.frame.size.width)
        self.pageController.currentPage = Int(pageNumber)
    } else {
      // Collection view
    }

}

Thanks.

回答4:

You need to check the scrollView inside the scrollViewDidEndDecelerating if it is your scroll view or your collection view. Just add an if scrollView == myScrollView before doing the 2 lines of code you have.

Your code shoudl look like this

func

scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    if scrollView == myScrollView {
        let pageNumber = round(scrollView.contentOffset.x / scrollView.frame.size.width)
        self.pageController.currentPage = Int(pageNumber)
    }
}

来源：https://stackoverflow.com/questions/44455450/ios-scrollviewdidenddecelerating-runs-for-both-scrollview-and-collectionview

标签

ios

objective-c

swift

scrollview

collectionview