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DiffUtil.DiffResult

public static class DiffUtil.DiffResult
extends Object

java.lang.Object
   ↳ 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

int NO_POSITION

Signifies an item not present in the list.

Public methods

int convertNewPositionToOld(int newListPosition)

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

int convertOldPositionToNew(int oldListPosition)

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

void dispatchUpdatesTo(ListUpdateCallback updateCallback)

Dispatches update operations to the given Callback.

void dispatchUpdatesTo(Adapter adapter)

Dispatches the update events to the given adapter.

Inherited methods

Constants

NO_POSITION

public static final int NO_POSITION

Signifies an item not present in the list.

Constant Value: -1 (0xffffffff)

Public methods

convertNewPositionToOld

public int convertNewPositionToOld (int newListPosition)

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

Returns
int Position of item in old list, or NO_POSITION if not present.

convertOldPositionToNew

public int convertOldPositionToNew (int oldListPosition)

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

Returns
int Position of item in new list, or NO_POSITION if not present.

dispatchUpdatesTo

public void dispatchUpdatesTo (ListUpdateCallback updateCallback)

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.

dispatchUpdatesTo

public void dispatchUpdatesTo (Adapter adapter)

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 Adapter: A RecyclerView adapter which was displaying the old list and will start displaying the new list.