ListAdapter

abstract class ListAdapter<T : Any!, VH : RecyclerView.ViewHolder!> : RecyclerView.Adapter<VH>
kotlin.Any
   ↳ androidx.recyclerview.widget.RecyclerView.Adapter<VH>
   ↳ androidx.recyclerview.widget.ListAdapter

RecyclerView.Adapter base class for presenting List data in a RecyclerView, including computing diffs between Lists on a background thread.

This class is a convenience wrapper around AsyncListDiffer that implements Adapter common default behavior for item access and counting.

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

A complete usage pattern with Room would look like this:

 @Dao interface UserDao { @Query("SELECT * FROM user ORDER BY lastName ASC") public abstract LiveData<List<User>> usersByLastName(); } class MyViewModel extends ViewModel { public final LiveData<List<User>> usersList; public MyViewModel(UserDao userDao) { usersList = userDao.usersByLastName(); } } class MyActivity extends AppCompatActivity { @Override public void onCreate(Bundle savedState) { super.onCreate(savedState); MyViewModel viewModel = ViewModelProviders.of(this).get(MyViewModel.class); RecyclerView recyclerView = findViewById(R.id.user_list); UserAdapter<User> adapter = new UserAdapter(); viewModel.usersList.observe(this, list -> adapter.submitList(list)); recyclerView.setAdapter(adapter); } } class UserAdapter extends ListAdapter<User, UserViewHolder> { public UserAdapter() { super(User.DIFF_CALLBACK); } @Override public void onBindViewHolder(UserViewHolder holder, int position) { holder.bindTo(getItem(position)); } public static final DiffUtil.ItemCallback<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 AsyncListDiffer, which provides custom mapping from diff events to adapter positions.

Summary

Protected constructors
<init>(diffCallback: DiffUtil.ItemCallback<T>)

Public methods
open Unit

Submits a new list to be diffed, and displayed.

open Int

Protected methods
open T
getItem(position: Int)

Inherited functions

Protected constructors

<init>

protected ListAdapter(diffCallback: DiffUtil.ItemCallback<T>)

<init>

protected ListAdapter(config: AsyncDifferConfig<T>)

Public methods

submitList

open fun submitList(list: MutableList<T>?): Unit

Submits a new list to be diffed, and displayed.

If a list is already being displayed, a diff will be computed on a background thread, which will dispatch Adapter.notifyItem events on the main thread.

Parameters
list MutableList<T>?: The new list to be displayed.

getItemCount

open fun getItemCount(): Int

Protected methods

getItem

protected open fun getItem(position: Int): T