DiffUtil.DiffResult

class DiffUtil.DiffResult


This class holds the information about the result of a calculateDiff call.

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

Summary

Constants

const Int

Signifies an item not present in the list.

Public functions

Int
convertNewPositionToOld(newListPosition: @IntRange(from = 0) Int)

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

Int
convertOldPositionToNew(oldListPosition: @IntRange(from = 0) Int)

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

Unit

Dispatches the update events to the given adapter.

Unit

Dispatches update operations to the given Callback.

Constants

NO_POSITION

Added in 1.0.0
const val NO_POSITION = -1: Int

Signifies an item not present in the list.

Public functions

convertNewPositionToOld

Added in 1.0.0
fun convertNewPositionToOld(newListPosition: @IntRange(from = 0) 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: @IntRange(from = 0) Int

Position of item in new list

Returns
Int

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

convertOldPositionToNew

Added in 1.0.0
fun convertOldPositionToNew(oldListPosition: @IntRange(from = 0) 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: @IntRange(from = 0) Int

Position of item in old list

Returns
Int

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

dispatchUpdatesTo

Added in 1.0.0
fun dispatchUpdatesTo(adapter: RecyclerView.Adapter): 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 to handle each modification manually.

Parameters
adapter: RecyclerView.Adapter

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

dispatchUpdatesTo

Added in 1.0.0
fun dispatchUpdatesTo(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.