PagedListAdapter

public abstract class PagedListAdapter<T extends Object, VH extends RecyclerView.ViewHolder> extends RecyclerView.Adapter

RecyclerView.Adapter base class for presenting paged data from androidx.paging.PagedLists in a RecyclerView.

This class is a convenience wrapper around AsyncPagedListDiffer that implements common default behavior for item counting, and listening to PagedList update callbacks.

While using a LiveData is an easy way to provide data to the adapter, it isn't required - you can use submitList when new lists are available.

PagedListAdapter listens to PagedList loading callbacks as pages are loaded, and uses DiffUtil on a background thread to compute fine grained updates as new PagedLists are received.

Handles both the internal paging of the list as more data is loaded, and updates in the form of new PagedLists.

A complete usage pattern with Room would look like this:

@Dao
interface UserDao {
    @Query("SELECT * FROM user ORDER BY lastName ASC")
    public abstract DataSource.Factory<Integer, User> usersByLastName();
}

class MyViewModel extends ViewModel {
    public final LiveData<PagedList<User>> usersList;
    public MyViewModel(UserDao userDao) {
        usersList = new LivePagedListBuilder&lt;>(
        userDao.usersByLastName(), /* page size */20).build();
    }
}

class MyActivity extends AppCompatActivity {
    @Override
    public void onCreate(Bundle savedState) {
        super.onCreate(savedState);
        MyViewModel viewModel = new ViewModelProvider(this).get(MyViewModel.class);
        RecyclerView recyclerView = findViewById(R.id.user_list);
        UserAdapter&lt;User> adapter = new UserAdapter();
        viewModel.usersList.observe(this, pagedList -> adapter.submitList(pagedList));
        recyclerView.setAdapter(adapter);
    }
}

class UserAdapter extends PagedListAdapter<User, UserViewHolder> {
    public UserAdapter() {
        super(DIFF_CALLBACK);
    }
    @Override
    public void onBindViewHolder(UserViewHolder holder, int position) {
        User user = getItem(position);
        if (user != null) {
            holder.bindTo(user);
        } else {
            // Null defines a placeholder item - PagedListAdapter will automatically invalidate
            // this row when the actual object is loaded from the database
            holder.clear();
        }
    }
    public static final DiffUtil.ItemCallback&lt;User> DIFF_CALLBACK =
            new DiffUtil.ItemCallback<User>() {
        @Override
        public boolean areItemsTheSame(@NonNull User oldUser, @NonNull User newUser) {
            // User properties may have changed if reloaded from the DB, but ID is fixed
            return oldUser.getId() == newUser.getId();
        }
        @Override
        public boolean areContentsTheSame(@NonNull User oldUser, @NonNull User newUser) {
            // NOTE: if you use equals, your object must properly override Object#equals()
            // Incorrectly returning false here will result in too many animations.
            return oldUser.equals(newUser);
        }
    }
}

Advanced users that wish for more control over adapter behavior, or to provide a specific base class should refer to AsyncPagedListDiffer, which provides the mapping from paging events to adapter-friendly callbacks.

Summary

Public fields

@Nullable
public @Nullable PagedList<@NonNull T> currentList

Public methods

@NonNull
public void addLoadStateListener(
    @NonNull Function2<@NonNull LoadType, @NonNull LoadState, Unit> listener
)

@NonNull
public int getItemCount()

@NonNull
public void onCurrentListChanged(@Nullable PagedList<@NonNull T> currentList)

@NonNull
public void onCurrentListChanged(
    @Nullable PagedList<@NonNull T> previousList,
    @Nullable PagedList<@NonNull T> currentList
)

@NonNull
public void removeLoadStateListener(
    @NonNull Function2<@NonNull LoadType, @NonNull LoadState, Unit> listener
)

@NonNull
public void submitList(@Nullable PagedList<@NonNull T> pagedList)

@NonNull
public void submitList(
    @Nullable PagedList<@NonNull T> pagedList,
    @Nullable Runnable commitCallback
)

@NonNull
public final ConcatAdapter withLoadStateFooter(@NonNull LoadStateAdapter<@NonNull ?> footer)

@NonNull
public final ConcatAdapter withLoadStateHeader(@NonNull LoadStateAdapter<@NonNull ?> header)

@NonNull
public final ConcatAdapter withLoadStateHeaderAndFooter(
    @NonNull LoadStateAdapter<@NonNull ?> header,
    @NonNull LoadStateAdapter<@NonNull ?> footer
)