PagedListAdapter
abstract classPagedListAdapter<T : Any, VH : RecyclerView.ViewHolder> : RecyclerView.Adapter<VH>
kotlin.Any | ||
↳ | androidx.recyclerview.widget.RecyclerView.Adapter<VH> | |
↳ | androidx.paging.PagedListAdapter |
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<>( 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<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<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
Protected constructors | |
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<init>(diffCallback: DiffUtil.ItemCallback<T>) Creates a PagedListAdapter with default threading and androidx.recyclerview.widget.ListUpdateCallback. |
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<init>(config: AsyncDifferConfig<T>) |
Public methods | |
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open Unit |
addLoadStateListener(listener: (LoadType, LoadState) -> Unit) Add a LoadState listener to observe the loading state of the current PagedList. |
open Int | |
open Unit |
onCurrentListChanged(currentList: PagedList<T>?) Called when the current PagedList is updated. |
open Unit |
onCurrentListChanged(previousList: PagedList<T>?, currentList: PagedList<T>?) Called when the current PagedList is updated. |
open Unit |
removeLoadStateListener(listener: (LoadType, LoadState) -> Unit) Remove a previously registered LoadState listener. |
open Unit |
submitList(pagedList: PagedList<T>?) Set the new list to be displayed. |
open Unit |
submitList(pagedList: PagedList<T>?, commitCallback: Runnable?) Set the new list to be displayed. |
ConcatAdapter |
Create a ConcatAdapter with the provided LoadStateAdapters displaying the LoadType.APPEND as a list item at the start of the presented list. |
ConcatAdapter |
withLoadStateHeader(header: LoadStateAdapter<*>) Create a ConcatAdapter with the provided LoadStateAdapters displaying the LoadType.PREPEND as a list item at the end of the presented list. |
ConcatAdapter |
Create a ConcatAdapter with the provided LoadStateAdapters displaying the LoadType.PREPEND and LoadType.APPENDs as list items at the start and end respectively. |
Protected methods | |
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open T? |
Inherited functions | |
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