CODEWITHSUNDEEP
iosswiftuiscrollviewuicollectionviewuicollectionviewlayout
coolly
coolly

Reputation: 353

How to check in UICollectionViewFlowLayout that in which direction the uicollectionview is scrolling? (Swift)

I knew how to check the direction using scroll view delegate methods. But unfortunately, I have a situation where I have to do the same in UICollectionViewFlowLayout but I can't access with scroll view delegate methods. I tried the ways to check(inside custom layout) in which direction collection view is scrolling, but there was no luck. Please help me in this case.

Further more details: I want to check the condition inside the custom layout. If the scroll direction is vertical. I want to find is it going top or bottom.

Upvotes: 0

Views: 2002

Answers (2)

Bartando
Bartando

Reputation: 748

Without any protocols or without UIScrollViewDelegate. You can use this in your custom UICollectionViewFlow.

Enum for better code

enum ScrollDirection {
    case left
    case right
}

And then the function itself which you can use anytime

func getScrollDirection() -> ScrollDirection? {
    guard let collectionView = collectionView else { return nil }

    let scrollVelocity = collectionView.panGestureRecognizer.velocity(in: collectionView.superview)
    if (scrollVelocity.x > 0.0) {
        return .right
    } else if (scrollVelocity.x < 0.0) {
        return .left
    } else {
        return nil
    }
}

The function may return nil in some cases so be sure to check it if needed

Use like this

if getScrollDirection() == .left

Upvotes: 3

Nirav D
Nirav D

Reputation: 72450

Add one method with your CustomFlowLayout and with scrollViewDidScroll method call it.

class CustomFlowLayout: UICollectionViewFlowLayout {

    var currentScrollDirection = ""

    func currentScroll(direction: String) {
        currentScrollDirection = direction
    }
}

Now implement scrollViewDidScroll method with your ViewController and call the currentScroll method with CustomFlowLayout.

var lastContentOffset = CGPoint.zero
func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let currentOffset = scrollView.contentOffset
    var scrollDirection = (currentOffset.y > self.lastContentOffset.y) ? "Down" : "Up"
    if let flowLayout = collectionView.collectionViewLayout as? CustomFlowLayout {
        flowLayout.currentScroll(direction: scrollDirection) 
    }
    self.lastContentOffset = currentOffset
}

Upvotes: 1

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