DiffResult

open class DiffResult
kotlin.Any
   ↳ androidx.recyclerview.widget.DiffUtil.DiffResult

This class holds the information about the result of a DiffUtil#calculateDiff(Callback, boolean) call.

You can consume the updates in a DiffResult via dispatchUpdatesTo(ListUpdateCallback) or directly stream the results into a RecyclerView.Adapter via dispatchUpdatesTo(RecyclerView.Adapter).

Summary

Constants
static Int

Signifies an item not present in the list.

Public methods
open Int
convertNewPositionToOld(newListPosition: Int)

Given a position in the new list, returns the position in the old list, or NO_POSITION if it was removed.

open Int
convertOldPositionToNew(oldListPosition: Int)

Given a position in the old list, returns the position in the new list, or NO_POSITION if it was removed.

open Unit

Dispatches the update events to the given adapter.

open Unit
dispatchUpdatesTo(@NonNull updateCallback: ListUpdateCallback)

Dispatches update operations to the given Callback.

Constants

NO_POSITION

static val NO_POSITION: Int

Signifies an item not present in the list.

Value: -1

Public methods

convertNewPositionToOld

open fun convertNewPositionToOld(newListPosition: Int): Int

Given a position in the new list, returns the position in the old list, or NO_POSITION if it was removed.

Parameters
newListPosition Int: Position of item in new list
Return
Int: Position of item in old list, or NO_POSITION if not present.

convertOldPositionToNew

open fun convertOldPositionToNew(oldListPosition: Int): Int

Given a position in the old list, returns the position in the new list, or NO_POSITION if it was removed.

Parameters
oldListPosition Int: Position of item in old list
Return
Int: Position of item in new list, or NO_POSITION if not present.

dispatchUpdatesTo

open fun dispatchUpdatesTo(@NonNull adapter: RecyclerView.Adapter<RecyclerView.ViewHolder!>): Unit

Dispatches the update events to the given adapter.

For example, if you have an Adapter that is backed by a List, you can swap the list with the new one then call this method to dispatch all updates to the RecyclerView.

 List oldList = mAdapter.getData(); DiffResult result = DiffUtil.calculateDiff(new MyCallback(oldList, newList)); mAdapter.setData(newList); result.dispatchUpdatesTo(mAdapter); 

Note that the RecyclerView requires you to dispatch adapter updates immediately when you change the data (you cannot defer notify* calls). The usage above adheres to this rule because updates are sent to the adapter right after the backing data is changed, before RecyclerView tries to read it.

On the other hand, if you have another AdapterDataObserver that tries to process events synchronously, this may confuse that observer because the list is instantly moved to its final state while the adapter updates are dispatched later on, one by one. If you have such an AdapterDataObserver, you can use dispatchUpdatesTo(ListUpdateCallback) to handle each modification manually.

Parameters
adapter RecyclerView.Adapter<RecyclerView.ViewHolder!>: A RecyclerView adapter which was displaying the old list and will start displaying the new list.

dispatchUpdatesTo

open fun dispatchUpdatesTo(@NonNull updateCallback: ListUpdateCallback): Unit

Dispatches update operations to the given Callback.

These updates are atomic such that the first update call affects every update call that comes after it (the same as RecyclerView).

Parameters
updateCallback ListUpdateCallback: The callback to receive the update operations.