Package 

Class ListAdapter

  • 
public abstract class ListAdapter<T, VH extends RecyclerView.ViewHolder>
extends RecyclerView.Adapter<VH>

    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 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 = new ViewModelProvider(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 AsyncListDiffer, which provides custom mapping from diff events to adapter positions.

    • Method Summary

      Modifier and Type Method Description
      void submitList(@Nullable() List<T> list) Submits a new list to be diffed, and displayed.
      void submitList(@Nullable() List<T> list, @Nullable() Runnable commitCallback) Set the new list to be displayed.
      int getItemCount() Returns the total number of items in the data set held by the adapter.
      List<T> getCurrentList() Get the current List - any diffing to present this list has already been computed anddispatched via the ListUpdateCallback.
      void onCurrentListChanged(@NonNull() List<T> previousList, @NonNull() List<T> currentList) Called when the current List is updated.

      • Methods inherited from class tds.androidx.recyclerview.widget.RecyclerView.Adapter

        bindViewHolder, createViewHolder, findRelativeAdapterPositionIn, getItemId, getItemViewType, getStateRestorationPolicy, hasObservers, hasStableIds, notifyDataSetChanged, notifyItemChanged, notifyItemChanged, notifyItemInserted, notifyItemMoved, notifyItemRangeChanged, notifyItemRangeChanged, notifyItemRangeInserted, notifyItemRangeRemoved, notifyItemRemoved, onAttachedToRecyclerView, onBindViewHolder, onBindViewHolder, onCreateViewHolder, onDetachedFromRecyclerView, onFailedToRecycleView, onViewAttachedToWindow, onViewDetachedFromWindow, onViewRecycled, registerAdapterDataObserver, setHasStableIds, setStateRestorationPolicy, unregisterAdapterDataObserver

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Method Detail

      • submitList

         void submitList(@Nullable() List<T> list)

        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, whichwill dispatch Adapter.notifyItem events on the main thread.

        Parameters:
        list - The new list to be displayed.

      • submitList

         void submitList(@Nullable() List<T> list, @Nullable() Runnable commitCallback)

        Set the new list to be displayed.

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

        The commit callback can be used to know when the List is committed, but note that itmay not be executed. If List B is submitted immediately after List A, and iscommitted directly, the callback associated with List A will not be run.

        Parameters:
        list - The new list to be displayed.
        commitCallback - Optional runnable that is executed when the List is committed, ifit is committed.

      • getItemCount

         int getItemCount()

        Returns the total number of items in the data set held by the adapter.

      • getCurrentList

        @NonNull() List<T> getCurrentList()

        Get the current List - any diffing to present this list has already been computed anddispatched via the ListUpdateCallback.

        If a null List, or no List has been submitted, an empty list will be returned.

        The returned list may not be mutated - mutations to content must be done through submitList.

      • onCurrentListChanged

         void onCurrentListChanged(@NonNull() List<T> previousList, @NonNull() List<T> currentList)

        Called when the current List is updated.

        If a null List is passed to submitList, or no List has beensubmitted, the current List is represented as an empty List.

        Parameters:
        previousList - List that was displayed previously.
        currentList - new List being displayed, will be empty if {@code null} was passed tosubmitList.