Swift: How to refresh UICollectionView layout after rotation of the device

Question

I used UICollectionView (flowlayout) to build a simple layout. the width for each cell is set to the width of screen using self.view.frame.width

but whe

Answer 1

My Code :

override func viewWillLayoutSubviews() {
   super.viewWillLayoutSubviews()
   self.collectionView.collectionViewLayout.invalidateLayout()
}

Will work correctly!!!

Answer 2

To update UICollectionViewLayout, traitCollectionDidChange method might be used as well:

override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
    super.traitCollectionDidChange(previousTraitCollection)

    guard previousTraitCollection != nil else { return }
    collectionView?.collectionViewLayout.invalidateLayout()
}

Answer 3

The viewWillLayoutSubviews() did not work for me. Neither did viewDidLayoutSubviews(). Both made the app go into an infinite loop which I checked using a print command.

One of the ways that do work is

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
// Reload here
}

Answer 4

I was also having some problem but then it got solved using :

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        collectionViewFlowLayoutSetup(with: view.bounds.size.width)
        collectionView?.collectionViewLayout.invalidateLayout()
        collectionViewFlowLayoutSetup(with: size.width)
    }

    fileprivate func collectionViewFlowLayoutSetup(with Width: CGFloat){

        if let flowLayout = collectionViewLayout as? UICollectionViewFlowLayout {
            flowLayout.estimatedItemSize = CGSize(width: Width, height: 300)
        }

    }

Answer 5

Add this function:

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews() 
    myCollection.collectionViewLayout.invalidateLayout()
}

When you change the orientation, this function would be called.

Answer 6

you can update your UICollectionView Layout by using

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    if isLandscape {
        return CGSizeMake(yourLandscapeWidth, yourLandscapeHeight)
    }
    else {
        return CGSizeMake(yourNonLandscapeWidth, yourNonLandscapeHeight)
    }
}