java - 通过检查光标是否为空来设置textview和recycleview的可见性

我正在尝试添加消息说没有数据和从光标获取数据的recycleview为空
我尝试了许多解决方案，但没有任何效果

这是MainActivity：

public class MainActivity extends AppCompatActivity implements
        LoaderManager.LoaderCallbacks<Cursor> {

    private static final String TAG = MainActivity.class.getSimpleName();
    private static final int INVENTORY_LOADER_ID = 0;

    private CursorAdapter mAdapter;
    RecyclerView mRecyclerView;

    TextView emptyList;

    Cursor inventoryData;

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

        mRecyclerView = (RecyclerView) findViewById(R.id.inventories);
        emptyList = (TextView) findViewById(R.id.empty_list);

        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

        mAdapter = new CursorAdapter(this, this, this);
        mRecyclerView.setAdapter(mAdapter);

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

    }


    @Override
    protected void onResume() {
        super.onResume();

        getSupportLoaderManager().restartLoader(INVENTORY_LOADER_ID, null, this);
    }

    @Override
    public Loader<Cursor> onCreateLoader(int id, final Bundle loaderArgs) {

        return new AsyncTaskLoader<Cursor>(this) {

            Cursor inventoryData = null;

            @Override
            protected void onStartLoading() {
                if (inventoryData != null) {

                    emptyList.setVisibility(View.GONE);
                    deliverResult(inventoryData);
                } else  {
                    forceLoad();

                }
        }

            @Override
            public Cursor loadInBackground() {

                try {
                    return getContentResolver().query(InventoryContract.InventoryEntry.CONTENT_URI,
                            null,
                            null,
                            null,
                            InventoryContract.InventoryEntry.COLUMN_ID);

                } catch (Exception e) {
                    Log.e(TAG, "Failed to asynchronously load data.");
                    e.printStackTrace();
                    return null;
                }
            }

            public void deliverResult(Cursor data) {
                inventoryData = data;

                super.deliverResult(data);
            }
        };

    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        mAdapter.swapCursor(data);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        mAdapter.swapCursor(null);
    }

}

我在oncreate方法中尝试过此方法：

mRecyclerView.setEmptyView(emptyList);

但似乎不适用于recycleview，所以我尝试了：

if (inventoryData.isEmpty()) {
    mRecyclerView.setVisibility(View.GONE);
    emptyList.setVisibility(View.VISIBLE);
}
else {
    mRecyclerView.setVisibility(View.VISIBLE);
    emptyList.setVisibility(View.GONE);
}

但我无法解决isEmpty（）方法

我在加载程序的onStartLoading（）中尝试了以下代码：

@Override
protected void onStartLoading() {
    if (inventoryData != null) {

        emptyList.setVisibility(View.GONE);
        deliverResult(inventoryData);
    } else {
        forceLoad();

    }
}

当recycleview为空且不为空时，emptylist textview已消失，但在所有语句中均已消失

我在上面的代码中尝试了其他方法：

emptyList.setVisibility(View.VISIBLE);

但不起作用

我也试过这个：

if (mAdapter.getItemCount() == 0) {
    emptyList.setVisibility(View.VISIBLE);
} else {
    emptyList.setVisibility(View.GONE);
}

在oncreate方法中，但应用程序崩溃了

最佳答案

检查游标是否“有效”的方法是

((cursor != null) && (cursor.getCount() > 0))