RecylerView 不会删除最后一项

如何解决RecylerView 不会删除最后一项

我有一个连接到回收站视图的列表适配器。我使用调用 deleteItem() 的 SwipToDelete。 如果我删除一个项目，回收者视图中的列表条目将被删除。

问题：如果回收站视图中只有一项并且我尝试将其删除，则列表条目在回收站视图中仍然可见。但是只要重新启动应用程序它就消失了。

我认为 notifyItemRemoved() 应该处理它，就像有多个项目一样。

RepoListAdapter：

public class RepoListAdapter extends ListAdapter<Repo,RepoViewHolder> {

    private RecyclerView recyclerView;

    public RepoListAdapter(@NonNull DiffUtil.ItemCallback<Repo> diffCallback) {
        super(diffCallback);
    }

    @NonNull @Override
    public RepoViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup,int viewType) {
        return RepoViewHolder.create(viewGroup);
    }

    @Override
    public void onBindViewHolder(RepoViewHolder holder,int position) {
        Repo current = getItem(position);
        holder.bind(current.getName());
    }

    public static class RepoDiff extends DiffUtil.ItemCallback<Repo> {

        @Override
        public boolean areItemsTheSame(@NonNull Repo oldItem,@NonNull Repo newItem) {
            return oldItem == newItem;
        }

        @Override
        public boolean areContentsTheSame(@NonNull Repo oldItem,@NonNull Repo newItem) {
            return oldItem.getName().equals(newItem.getName());
        }
    }

    @Override
    public void onAttachedToRecyclerView(@NonNull RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);
        this.recyclerView = recyclerView;
    }

    public Context getContext() {
        return recyclerView.getContext();
    }

    public void deleteItem(int position) {
        Repo recentlyDeletedRepo = getItem(position);
        RepoViewModel repoViewModel = new ViewModelProvider((ViewModelStoreOwner) getContext()).get(RepoViewModel.class);
        repoViewModel.delete(recentlyDeletedRepo);
        notifyItemRemoved(position);
        notifyItemRangeRemoved(position,1);

        Snackbar snackbar = Snackbar.make(recyclerView,R.string.snackbar_undo,Snackbar.LENGTH_LONG);
        snackbar.setAction(R.string.snackbar_undo,v -> undoDelete(recentlyDeletedRepo,position));
        snackbar.show();
    }

    private void undoDelete(Repo recentlyDeletedRepo,int position) {
        RepoViewModel repoViewModel = new ViewModelProvider((ViewModelStoreOwner) getContext()).get(RepoViewModel.class);
        repoViewModel.insert(recentlyDeletedRepo);
        notifyItemInserted(position);
    }
}

RepoViewModel：

public class RepoViewModel extends AndroidViewModel {
    private final RepoRepository repoRepository;
    private final LiveData<List<Repo>> allRepos;
    private Repo currentRepo;

    public RepoViewModel(Application application) {
        super(application);
        repoRepository = new RepoRepository(application);
        allRepos = repoRepository.getAllRepos();
    }

    public Repo getCurrentRepo() {
        return currentRepo;
    }

    public void setCurrentRepo(Repo currentRepo) {
        this.currentRepo = currentRepo;
    }

    public LiveData<Repo> getRepoById(int id) {
        return repoRepository.getRepoById(id);
    }

    public LiveData<List<Repo>> getAllRepos() {
        return allRepos;
    }

    public long insert(Repo repo) {
        return repoRepository.insert(repo);
    }

    public void update(Repo repo) {
        repoRepository.update(repo);
    }

    public void delete(Repo repo) {
        repoRepository.delete(repo);
    }
}

项目片段：

public class ProjectsFragment extends Fragment {

    private RecyclerView recyclerView;
    private TextView textview_no_project;
    private RepoListAdapter repoListAdapter;

    @Override
    public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState) {
        FloatingActionButton floatingActionButton = ((MainActivity) requireActivity()).getFloatingActionButton();
        floatingActionButton.setVisibility(View.VISIBLE);

        return inflater.inflate(R.layout.fragment_projects,container,false);
    }

    public void onViewCreated(@NonNull View view,Bundle savedInstanceState) {
        super.onViewCreated(view,savedInstanceState);

        textview_no_project = view.findViewById(R.id.textview_no_project);
        repoListAdapter = new RepoListAdapter(new RepoListAdapter.RepoDiff());

        recyclerView = view.findViewById(R.id.recyclerview);
        recyclerView.setLayoutManager(new LinearLayoutManager(requireActivity()));
        DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(),DividerItemDecoration.VERTICAL);
        recyclerView.addItemDecoration(dividerItemDecoration);
        recyclerView.setAdapter(repoListAdapter);
        ItemTouchHelper itemTouchHelper = new
                ItemTouchHelper(new SwipeToDeleteCallback(repoListAdapter));
        itemTouchHelper.attachToRecyclerView(recyclerView);

        RepoViewModel repoViewModel = new ViewModelProvider(requireActivity()).get(RepoViewModel.class);
        repoViewModel.getAllRepos().observe(getViewLifecycleOwner(),this::onLoaded);
    }

    private void onLoaded(List<Repo> list){
        if (list.size() == 0) {
            textview_no_project.setVisibility(View.VISIBLE);
        }
        else {
            textview_no_project.setVisibility(View.INVISIBLE);
            repoListAdapter.submitList(list);
        }
    }
}

解决方法

试试notifyDataSetChanged();在您的适配器中