areItemsTheSame
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.
Return
True if the two items represent the same object or false if they are different.
Parameters
oldItem
The item in the old list.
newItem
The item in the new list.