/* * Copyright 2018 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package androidx.recyclerview.widget; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import java.util.List; /** * {@link RecyclerView.Adapter RecyclerView.Adapter} base class for presenting List data in a * {@link RecyclerView}, including computing diffs between Lists on a background thread. *
* This class is a convenience wrapper around {@link 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 {@link #submitList(List)} when new lists are available. *
* A complete usage pattern with Room would look like this: *
* {@literal @}Dao * interface UserDao { * {@literal @}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 { * {@literal @}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); * } * {@literal @}Override * public void onBindViewHolder(UserViewHolder holder, int position) { * holder.bindTo(getItem(position)); * } * public static final DiffUtil.ItemCallback<User> DIFF_CALLBACK = * new DiffUtil.ItemCallback<User>() { * {@literal @}Override * public boolean areItemsTheSame( * {@literal @}NonNull User oldUser, {@literal @}NonNull User newUser) { * // User properties may have changed if reloaded from the DB, but ID is fixed * return oldUser.getId() == newUser.getId(); * } * {@literal @}Override * public boolean areContentsTheSame( * {@literal @}NonNull User oldUser, {@literal @}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 {@link AsyncListDiffer}, which provides custom mapping from diff events * to adapter positions. * * @param
* 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.
*
* @param list The new list to be displayed.
*/
@SuppressWarnings("WeakerAccess")
public void submitList(@Nullable List