iPad keyboard navigation: where to initialize UIFocusHaloEffect

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Created Jul ’21

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WWDC21 Session Focus on iPad keyboard navigation says that we can use UIFocusHaloEffect to change the appearance of focused items.

On iPadOS, we can use this effect by assigning a UIFocusHaloEffect to the focusEffect property like so:

self.focusEffect = UIFocusHaloEffect()

What wasn't very clear is where should we put this code when working with UICollectionViewCell. I am doing it in the collectionView(_:canFocusItemAt:) method:

func collectionView(_ collectionView: UICollectionView, canFocusItemAt indexPath: IndexPath) -> Bool {
    guard #available(iOS 15.0, *) else { return false }
    guard let cell = collectionView.cellForItem(at: indexPath) as? FeedCollectionViewCell else { return false }
    if cell.focusEffect == nil {
        cell.focusEffect = UIFocusHaloEffect(roundedRect: cell.artworkImageView.frame,
                                             cornerRadius: cell.cornerRadius,
                                             curve: .continuous)
    }
    return true
}

Is this the best way to implement it?

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Answer 1

iOSDevDaniel OP

Aug ’21

I believe the best place to implement it is in the init of the cell class. Example:

class GenericCell: UICollectionViewCell {

    static let reuseIdentifier = "my-cell"
    override var canBecomeFocused: Bool { true }

    override init(frame: CGRect) {
        super.init(frame: frame)
        focusEffect = UIFocusHaloEffect()
        ...
    }
    ...
}

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