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我目前正在使用Firebase编写Android应用程序。我有一个具有城市属性的产品模型。 我运行下面的查询:Android Firebase orderByChild查询
mDatabaseReference = FirebaseDatabase.getInstance().getReference();
mDatabaseReference.keepSynced(true);
productQuery = mDatabaseReference.child("products")
.orderByChild("city").equalTo(mCurrentUser).limitToFirst(100);
这个查询检索所有数据库中的产品,无论城市。
我花了最近四个小时在SO上查看类似的问题,尝试查询函数+规则索引的不同组合,无济于事。 我有什么我称之为愚蠢的解决方案,重新复制城市产品树下的数据。不过,我猜测有一个更好的方法来利用orderByChild,如果我能得到一些帮助按城市查询数据,我将不胜感激。
感谢您的输入
这里的CityFeed片断 - 注意:我查mCurrentUserCity设置
public class CityFeedFragment extends BaseFragment {
private RecyclerView mRecyclerView;
private String mCurrentUserCity;
private FirebaseProductAdapter mAdapter;
private DatabaseReference mDatabaseReference;
private LinearLayoutManager mManager;
private Query productQuery;
private SwipeRefreshLayout mSwipeRefreshLayout;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_feed, container, false);
mDatabaseReference = FirebaseDatabase.getInstance().getReference();
mDatabaseReference.keepSynced(true);
retrieveCity();
fetchProducts();
mAdapter = new FirebaseProductAdapter(Product.class,
R.layout.feed_item, ProductViewHolder.class,
productQuery.getRef(), getContext(), false);
return view;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
mSwipeRefreshLayout = (SwipeRefreshLayout) view.findViewById(R.id.swipe_refresh_layout);
mRecyclerView.setAdapter(mAdapter);
mManager = new LinearLayoutManager(getActivity());
mManager.setReverseLayout(true);
mManager.setStackFromEnd(true);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.setLayoutManager(mManager);
mSwipeRefreshLayout.setOnRefreshListener(() -> {
fetchProducts();
mAdapter.notifyDataSetChanged();
mSwipeRefreshLayout.setRefreshing(false);
});
}
private void fetchProducts() {
productQuery = mDatabaseReference.child("products").orderByChild("city").equalTo(mCurrentUserCity);
}
private void retrieveCity() {
mDatabaseReference.child("users").child(getUid()).addListenerForSingleValueEvent(
new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
User user = dataSnapshot.getValue(User.class);
if (user == null) {
showToast(getResources().getString(R.string.empty_user));
} else {
mCurrentUserCity = user.getCity();
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
showToast(databaseError.toString());
Log.w("Cityfeed", "getUser:onCancelled", databaseError.toException());
}
}
);
}
}
请问您可以发布您的数据库结构的图片,我并不真正了解您的问题是什么。 –
另请参见:请包含在读取数据时再现问题的最小代码。您现在共享的代码仅创建一个查询,但尚未检索任何数据。如果你有一个监听器只能记录结果,那么没关系,但我仍然希望看到它。 –
完成,谢谢观看 – Ender