recyclerview 中的列表未排序

Question

我在数据库中有一个 phone 号码和消息对的列表。我想按选项菜单中的相应按钮后按 phone 数字或消息文本的相反顺序对列表进行排序。

我用 compare 实现了 Collections.sort，并用 notifyDataSetChanged() 更新了适配器。但是，当我按下按钮时，没有任何反应。作为测试，我尝试在 onViewCreated() 的末尾调用排序方法和 notifyDataSetChanged()，但也没有排序。

public class LogScreen extends Fragment implements LoaderManager.LoaderCallbacks<Cursor> {

    private static final int LOG_LOADER_ID = 0;
    private LogAdapter mLogAdapter;
    private RecyclerView mRecyclerView;

    List<LogEntryItem> mLogList = new ArrayList<>();


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {

        setHasOptionsMenu(true);
        return inflater.inflate(R.layout.fragment_log_screen, parent, false);
    }


    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        mRecyclerView = (RecyclerView) view.findViewById(R.id.recyclerview_log);

        int recyclerViewOrientation = LinearLayoutManager.VERTICAL;
        boolean shouldReverseLayout = false;

        LinearLayoutManager layoutManager = new LinearLayoutManager(getContext(), recyclerViewOrientation, shouldReverseLayout);
        mRecyclerView.setLayoutManager(layoutManager);

        mLogAdapter = new LogAdapter(getContext(), mLogList);
        mRecyclerView.setAdapter(mLogAdapter);

        getLoaderManager().initLoader(LOG_LOADER_ID, null, this);
    }


    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {

        super.onCreateOptionsMenu(menu, inflater);

        inflater.inflate(R.menu.menu_log_screen, menu);

        MenuItem buttonSortByPhone   = menu.findItem(R.id.log_screen_sort_by_phone);
        MenuItem buttonSortByMessage = menu.findItem(R.id.log_screen_sort_by_message);
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch (item.getItemId()) {
            case R.id.log_screen_sort_by_phone:
                reverseSortComparePhoneNumber();
                return true;

            case R.id.log_screen_sort_by_message:
                reverseSortCompareMessageSent();
                return true;

            default:
                break;
        }

        return false;
    }


    public void reverseSortComparePhoneNumber() {

        Collections.sort(mLogList, new Comparator<LogEntryItem>() {
            @Override
            public int compare(LogEntryItem itemA, LogEntryItem itemB) {
                return itemB.getPhoneNumber().compareTo(itemA.getPhoneNumber());
            }
        });

        mLogAdapter.notifyDataSetChanged();
    }


    public void reverseSortCompareMessageSent() {

        Collections.sort(mLogList, new Comparator<LogEntryItem>() {
            @Override
            public int compare(LogEntryItem itemA, LogEntryItem itemB) {
                return itemB.getMessageSent().compareTo(itemA.getMessageSent());
            }
        });

        mLogAdapter.notifyDataSetChanged();
    }


    @NonNull
    @Override
    public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
        return new CursorLoader(getContext(), LogContentProvider.CONTENT_URI, null, null, null, null);
    }


    @Override
    public void onLoadFinished(@NonNull Loader<Cursor> loader, Cursor cursor) {

        List<LogEntryItem> list = new ArrayList<>();

        while (cursor.moveToNext()) {
            int index1 = cursor.getColumnIndex(LogDBHelper.COLUMN_PHONE_NUMBER);
            int index2 = cursor.getColumnIndex(LogDBHelper.COLUMN_MESSAGE);

            String phoneNumber = cursor.getString(index1);
            String messageSent = cursor.getString(index2);

            LogEntryItem logEntry = new LogEntryItem(phoneNumber, messageSent);
            list.add(logEntry);
        }

        mLogAdapter = new LogAdapter(getContext(), list);
        mRecyclerView.setAdapter(mLogAdapter);
    }


    @Override
    public void onLoaderReset(@NonNull Loader<Cursor> loader) {
    }

}

为什么 Collections.sort 没有对我的列表进行排序？

Answer 1

对于按字典顺序对您的 LogEntryItem 消息进行反向排序：

class SortbyMessage implements Comparator<LogEntryItem> { 
    @Override
    public int compare(LogEntryItem a, LogEntryItem b) { 
        return a.getMessageSent().compareTo(b.getMessageSent());
    } 
}

现在你可以这样使用了

Comparator comparator = Collections.reverseOrder(new SortbyMessage()); 
Collections.sort(ar, comparator);

除了

，数字排序与上面类似

return a.getPhoneNumber() - b.getPhoneNumber();

或在您的 reverseSortComparePhoneNumber 方法中将您的 return 更改为

itemB.getPhoneNumber() - itemA.getPhoneNumber();

Answer 2

难道是因为onLoadFinished中的代码？我不喜欢加载程序，但你在那里设置了一个适配器，用于传递局部变量 list 的回收器视图。这意味着调用此代码后，您的适配器将不再绑定到 mLogList。

recyclerview 中的列表未排序

List in recyclerview not sorting

java

android

android-fragments

android-optionsmenu