How to add custom swipe actions to a UICollectionViewListCell?

Published on: June 24, 2020

In iOS 14 Apple added the ability for developers to create collection views that look and feel like table views, except they are far, far more powerful. To do this, Apple introduced a new UICollectionViewCell subclass called UICollectionViewListCell. This new cell class allows us to implement several tableviewcell-like principles, including swipe actions.

You can add both leading and trailing swipe actions to a cell by assigning a UISwipeActionsConfigurationProvider instance to the collection view's UICollectionLayoutListConfiguration object's leadingSwipeActionsConfigurationProvider and trailingSwipeActionsConfigurationProvider properties. This swipe actions provider is expected to return an instance of UISwipeActionsConfiguration. A UISwipeActionsConfiguration is created using an array of one or more UIContextualAction instances.

You can customize the icon, title, and background color of a contextual icon as needed. Setting an image and background is optional but you are required to pass a title to the UIContextualAction initializer.

Let's look at an example of how you can add a simple trailing swipe action to a list configuration instance:

let listConfig = UICollectionLayoutListConfiguration(appearance: .insetGrouped)

listConfig.trailingSwipeActionsConfigurationProvider = { [weak self] indexPath in 
  guard let self = self else { return nil }

  let model = self.dataSource[indexPath.row] // get the model for the given index path from your data source

  let actionHandler: UIContextualAction.Handler = { action, view, completion in
    model.isDone = true
    self.collectionView.reloadItems(at: [indexPath])

  let action = UIContextualAction(style: .normal, title: "Done!", handler: actionHandler)
  action.image = UIImage(systemName: "checkmark")
  action.backgroundColor = .systemGreen

  return UISwipeActionsConfiguration(actions: [action])

let listLayout = UICollectionViewCompositionalLayout.list(using: listConfig)

collectionView = UICollectionView(frame: .zero, collectionViewLayout: listLayout)

This is a very simple configuration that adds a single trailing action to every cell in the list. The action is configured to have a green background and has a checkmark icon. Note that when you set an image on the action, the tite is hidden from view on iOS. It's still used for accessibillity so make sure to set a good title, even if you plan on using an image in the UI.

Notice that I assign listConfig.trailingSwipeActionsConfigurationProvider before creating my listLayout property. Since UICollectionLayoutListConfiguration is a struct you need to make sure it's fully configured before using it to create a list layout. If you create the list layout first, it will use its own copy of your list configuration and updates you make to your initial instance won't carry over to the UICollectionViewCompositionalLayout because it uses its own copy of the configuration object.

You can return different configurations depending on the index path that you're supplying the swipe actions for. If you don't want to have any swipe actions for a certain index path, you can return nil from the closure that's used to configure your swipe actions.

Note that I created a .normal contextual action. The other option here is .desctructive to indicate that an action might destruct data.

The action handler that's passed to UIContextualAction receives a reference to the action that triggered it, the view that this occured in and a completion handler that you must call.

You also receive a completion handler in the action handler. You must call this handler when you're done handling the action and pass true if you handled the action successfully. If you failed to successfully handle the action, you must pass false. This allows the system to perform any tasks (if needed) related to whether you were able to handle the action or not.


Swift wwdc2020

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