Is there a recommended image size for UIContextualAction icons?

Question

New in iOS 11, UIContextualAction provides a convenient way to implement swipe actions on UITableView cells, with a title and/or image icon.

I haven't found any mention in the Human Interface Guidelines of the image used by UIContextualAction. Does any information exist that defines a standard size or other design guidance for this icon image?

I tried to figure this out by testing a few image sizes to see if iOS would scale it to a consistent size, but it seems to just display whatever you give it with no scaling or cropping, so that didn't provide any clues.

Answer 1

I use 30 by 30. You can render your image down to that size in code easily enough.

    let d = UIContextualAction(style: .destructive, title: nil) {
        action, view, completion in
        // ... whatever ...
        completion(true)
    }
    d.image = UIGraphicsImageRenderer(size: CGSize(width: 30, height: 30)).image { _ in
        UIImage(named: "trash")?.draw(in: CGRect(x: 0, y: 0, width: 30, height: 30))
    }