如何从SearchView过滤ListView（SimpleCursorAdapter）？

Question

我尝试处理ListView和SimpleCursorAdapter并遇到以下问题：我有ListView with SimpleCursorAdapter和SearchView。我尝试根据SearchView中的文本过滤ListView中的数据（数据库中的数据）。但是当我在模拟器上启动应用程序时，应用程序崩溃并出现NullPointerException。错误可能是什么？我做的一切都好吗？

public class ListViewFragmentActivity extends AppCompatActivity implements LoaderCallbacks<Cursor> {

private static final int CM_DELETE_ID = 1;

public ListView listViewData;
public Button mAddButton, mViewButtonProject, mViewButtonStaff;
public Bundle mBundle;

private DatabaseHelper db;

private SimpleCursorAdapter scAdapter;

private android.support.v7.widget.SearchView sv;

public void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.list_view);

    drawNavigationDrawer();

    returnBundle(savedInstanceState);

    final Context context = this;

    db = new ProjectDatabase(this);
    db.open();

    String[] from = new String[] { db.COLUMN_NAME, db.COLUMN_DESCRIPTION };
    int[] to = new int[] { R.id.textViewName, R.id.textViewDescription };

    scAdapter = new SimpleCursorAdapter(this, R.layout.list_view_item, null, from, to, 0);
    listViewData = (ListView) findViewById(R.id.listViewData);
    listViewData.setAdapter(scAdapter);

    sv = (android.support.v7.widget.SearchView) findViewById(R.id.action_search);
    sv.setOnQueryTextListener(new android.support.v7.widget.SearchView.OnQueryTextListener() {
        @Override
        public boolean onQueryTextSubmit(String query) {

            return false;
        }

        @Override
        public boolean onQueryTextChange(String newText) {
            listViewData = (ListView) findViewById(R.id.listViewData);
            SimpleCursorAdapter filterAdapter = (SimpleCursorAdapter)listViewData.getAdapter();
            filterAdapter.getFilter().filter(newText);

            return false;
        }
    });

    registerForContextMenu(listViewData);

    getSupportLoaderManager().initLoader(0, null, this);

}

这就是我在代码中执行的任务。我还没有做过什么？

NullPointerException错误引用此行：sv.setOnQueryTextListener(new android.support.v7.widget.SearchView.OnQueryTextListener() {...}

我将非常感谢任何帮助。

upd：我试试这个：

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu, menu);

    MenuItem searchItem = menu.findItem(R.id.search);
    SearchView sv = (SearchView) MenuItemCompat.getActionView(searchItem);

    sv.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
        @Override
        public boolean onQueryTextSubmit(String query) {

            return false;
        }

        @Override
        public boolean onQueryTextChange(final String newText) {
            scAdapter.setFilterQueryProvider(new FilterQueryProvider() {
                @Override
                public Cursor runQuery(CharSequence constraint) {
                    Cursor cursor = dbConnector.getFilteredData(constraint.toString()); 
            return cursor;
                }
            });
            return false;
        }
    });

    return true;
}

在DB类中：

public Cursor getFilteredContacts(String filter) {
    return database.query(...);
}