Overview

Callback for calculating the diff between two non-null items in a list.

DiffUtil.Callback serves two roles - list indexing, and item diffing. ItemCallback handles just the second of these, which allows separation of code that indexes into an array or List from the presentation-layer and content specific diffing code.

Summary

Constructors

Methods

Called to check whether two objects represent the same item.

For example, if your items have unique ids, this method should check their id equality.

Note: null items in the list are assumed to be the same as another null item and are assumed to not be the same as a non-null item. This callback will not be invoked for either of those cases.

Parameters:

oldItem: The item in the old list.
newItem: The item in the new list.

Returns:

True if the two items represent the same object or false if they are different.

See also: DiffUtil.Callback.areItemsTheSame(int, int)

Called to check whether two items have the same data.

This information is used to detect if the contents of an item have changed.

This method to check equality instead of equals so that you can change its behavior depending on your UI.

For example, if you are using DiffUtil with a RecyclerView.Adapter, you should return whether the items' visual representations are the same.

This method is called only if DiffUtil.ItemCallback returns true for these items.

Note: Two null items are assumed to represent the same contents. This callback will not be invoked for this case.

Parameters:

oldItem: The item in the old list.
newItem: The item in the new list.

Returns:

True if the contents of the items are the same or false if they are different.

See also: DiffUtil.Callback.areContentsTheSame(int, int)

When DiffUtil.ItemCallback returns true for two items and DiffUtil.ItemCallback returns false for them, this method is called to get a payload about the change.

For example, if you are using DiffUtil with RecyclerView, you can return the particular field that changed in the item and your ItemAnimator can use that information to run the correct animation.

Default implementation returns null.

See also: DiffUtil.Callback.getChangePayload(int, int)