java - 更新回收者 View 数据

Question

几天以来，我尝试在 viewpager2 中处理 recyclerview 中的数据。 viewpager 有一个适配器管理 recyclerview 中的数据。但我尝试做的一切似乎都不起作用。也许我误解了目的或其他什么。我希望你能帮助我。

此 Activity 管理 viewpager 及其适配器。它将数据发送到内部recyclerview:

public class AudioFilePanel extends AppCompatActivity
{
    private String currentTab;
    private ViewPagerAdapter adapter;
    private ViewPager2 viewPager;
    private TabLayout tabLayout;
    private Map<String, List<String>> content;

    private String path;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_audio_file_panel);

        viewPager = findViewById(R.id.view_pager2);
        tabLayout = findViewById(R.id.tabs);
        Button addFilesByTag = findViewById(R.id.add_files_with_tag);

        if (null == currentTab)
        {
            currentTab = "music";
        }

        content = listByTag();

        adapter = new ViewPagerAdapter(getApplicationContext(), new ArrayList<>(content.values()));
        viewPager.setAdapter(adapter);
        new TabLayoutMediator(tabLayout, viewPager,
            (tab, position) -> tab.setText(content.keySet().toArray()[position].toString())).attach();

        tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener()
        {
            @Override
            public void onTabSelected(TabLayout.Tab tab)
            {
                currentTab = tab.getText().toString();
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab)
            {
            }

            @Override
            public void onTabReselected(TabLayout.Tab tab)
            {
            }
        });
        addFilesByTag.setOnClickListener(l ->
        {
            Intent fileBrowser = new Intent(AudioFilePanel.this, FileBrowser.class);
            startActivityForResult(fileBrowser, 1);
        });
    }

    private void updateViweData()
    {
        content = listByTag();
        adapter = new ViewPagerAdapter(getApplicationContext(), new ArrayList<>(content.values()));
        viewPager.setAdapter(adapter);
    }

    private Map<String, List<String>> listByTag()
    {
        Map<String, List<String>> result = new HashMap<>();
        DirectoryDao dao = new DirectoryDao(getApplicationContext());
        String[] categories = {"music", "ambience", "effect"};

        for (String category : categories)
        {
            List<String> directories =
                dao.getDirectoriesForCategory(category).stream().map(Directory::getPath).collect(Collectors.toList());

            result.put(category, directories);
        }
        return result;
    }

这是 View 寻呼机适配器。它直接从 Activity 中获取数据，并且每次单击某个项目时都应该触发内部回收器 View 中的数据更新。参见第 118-128 行:

public class ViewPagerAdapter extends RecyclerView.Adapter<ViewPagerAdapter.ViewHolder>
{

    private List<List<String>> filesListsByCategory;
    private LayoutInflater mInflater;
    private Context ctx;
    private ItemListAdapter adapter;
    private List<String> categoryFiles;

    public ViewPagerAdapter(Context context, List<List<String>> data)
    {
        this.mInflater = LayoutInflater.from(context);
        this.filesListsByCategory = data;
        this.ctx = context;
    }

    @NotNull
    @Override
    public ViewHolder onCreateViewHolder(@NotNull ViewGroup parent, int viewType)
    {
        return new ViewHolder(mInflater.inflate(R.layout.item_viewpager, parent, false));
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position)
    {
        FileBrowserService fbs = new FileBrowserService();
        categoryFiles = filesListsByCategory.get(position);

        adapter = new ItemListAdapter(categoryFiles, new ItemList.OnListFragmentInteractionListener()
        {
            @Override
            public void onListFragmentInteraction(String item)
            {
                categoryFiles = fbs.getFiles(categoryFiles.get(position));
                categoryFiles.add(0, "previous directory");
                updateUi(adapter, holder);
            }
        });
        holder.myView.setAdapter(adapter);
    }

    private void updateUi(ItemListAdapter adapter, ViewHolder holder)
    {
        adapter.notifyDataSetChanged();
        holder.myView.setAdapter(adapter);
    }

    @Override
    public int getItemCount()
    {
        return filesListsByCategory.size();
    }

    class ViewHolder extends RecyclerView.ViewHolder
    {
        RecyclerView myView;
        RelativeLayout relativeLayout;

        ViewHolder(View itemView)
        {
            super(itemView);

            myView = itemView.findViewById(R.id.my_list);
            myView.setLayoutManager(new LinearLayoutManager(ctx));
            relativeLayout = itemView.findViewById(R.id.container);
        }
    }
}

它是内部recyclerview的适配器。它仅代表一个元素列表:

public class ItemListAdapter extends RecyclerView.Adapter<ItemListAdapter.ViewHolder>
{
    private List<String> files;
    private final OnListFragmentInteractionListener mListener;

    public ItemListAdapter(List<String> items, OnListFragmentInteractionListener listener)
    {
        files = items;
        mListener = listener;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
    {
        return new ViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.fragment_item, parent, false));
    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, int position)
    {
        holder.file = files.get(position);
        holder.mContentView.setText(files.get(position));

        holder.mView.setOnClickListener(v ->
        {
            if (null != mListener)
            {
                // Notify the active callbacks interface (the activity, if the
                // fragment is attached to one) that an item has been selected.
                mListener.onListFragmentInteraction(holder.file);

            }
        });
    }

    @Override
    public int getItemCount()
    {
        return files.size();
    }

    class ViewHolder extends RecyclerView.ViewHolder
    {
        private final View mView;
        private final TextView mContentView;
        private String file;

        private ViewHolder(View view)
        {
            super(view);
            mView = view;
            mContentView = view.findViewById(R.id.content);
        }
    }
}

最后一件事是 ItemList fragment 。

public class ItemList extends Fragment
{

    // TODO: Customize parameter argument names
    private static final String ARG_COLUMN_COUNT = "column-count";
    // TODO: Customize parameters
    private int mColumnCount = 1;
    private OnListFragmentInteractionListener mListener;

    /**
     * Mandatory empty constructor for the fragment manager to instantiate the fragment (e.g. upon screen orientation
     * changes).
     */
    public ItemList()
    {
    }

    // TODO: Customize parameter initialization
    @SuppressWarnings("unused")
    public static ItemList newInstance(int columnCount)
    {
        ItemList fragment = new ItemList();
        Bundle args = new Bundle();
        args.putInt(ARG_COLUMN_COUNT, columnCount);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onAttach(Context context)
    {
        super.onAttach(context);
        if (context instanceof OnListFragmentInteractionListener)
        {
            mListener = (OnListFragmentInteractionListener) context;
        } else
        {
            throw new RuntimeException(context.toString() + " must implement OnListFragmentInteractionListener");
        }
    }

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        if (getArguments() != null)
        {
            mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        View view = inflater.inflate(R.layout.fragment_item_list, container, false);

        if (view instanceof RecyclerView)
        {
            Context context = view.getContext();
            RecyclerView recyclerView = (RecyclerView) view;
            if (mColumnCount <= 1)
            {
                recyclerView.setLayoutManager(new LinearLayoutManager(context));
            } else
            {
                recyclerView.setLayoutManager(new GridLayoutManager(context, mColumnCount));
            }
            recyclerView.setAdapter(new ItemListAdapter(getArguments().getStringArrayList("list"), mListener));
        }
        return view;
    }

    @Override
    public void onDetach()
    {
        super.onDetach();
        mListener = null;
    }

    /**
     * This interface must be implemented by activities that contain this fragment to allow an interaction in this
     * fragment to be communicated to the activity and potentially other fragments contained in that activity.
     * <p/>
     * See the Android Training lesson
     * <a href= "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnListFragmentInteractionListener
    {
        // TODO: Update argument type and name
        void onListFragmentInteraction(String item);
    }
}

当我点击时，数据不会更新。我想要的是:

Answer 1

这就是你必须做的

将此方法添加到您的适配器类中

public void updateData(List<String> filesList, int flag) {
    if (flag == 0) { //append
        for (int i = 0; i < filesList.size(); i++) {
            files.add(messageList.get(i));
            notifyItemInserted(getItemCount());
        }
    } else { //clear all
        files.clear();
        notifyDataSetChanged();
    }
}

然后每当您需要更新回收 View 调用时，如下所示

mItemListAdapter.updateData(yourNewListOfItems, 0);

如果您需要像下面这样重置回收 View 调用

mItemListAdapter.updateData(null, 1);