DiffResult

NO_POSITION

static val NO_POSITION: Int

Signifies an item not present in the list.

Value: -1

convertNewPositionToOld

open fun convertNewPositionToOld(@IntRange(0) newListPosition: Int): Int

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

convertOldPositionToNew

open fun convertOldPositionToNew(@IntRange(0) oldListPosition: Int): Int

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

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.

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).