检索 1 周范围内的 Firebase 数据

Question

I want to retrieve Firebase data within a range of say 1 week. I can query and get data for a day like today, but how about for a range of say 1 week? This is the code that am currenly using for retrieving data for a given day

String mDate = DateFormat.getDateInstance().format(new Date());
    DatabaseReference reference = FirebaseDatabase.getInstance().getReference("expenses").child(onlineUserId);
    Query query = reference.orderByChild("date").equalTo(mDate);
    query.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            myDataList.clear();
            for (DataSnapshot snapshot :dataSnapshot.getChildren()){
                Data data = snapshot.getValue(Data.class);
                myDataList.add(data);

            }
            todayItemsAdapter.notifyDataSetChanged(); 
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });

I cannot find a way of retrieving data for a given range. Someone please help.

Answer 1

The Realtime Database is not designed for complex SQL-like queries.

Not sure if your question refers to grouping results by week. If all you need is a set of results that start and on a certain date and end on another date, you can use startAt(...) and endAt(...) like described in this answer or the spec .

If you need anything more complex than that, you need to

1. either take all results and filter them in your front end/app code

2. or use a Cloud Function to do the filtering on the server and passing the results to the front end.

3. (Not recommended) You can record the week number (ie 45_2020) as a separate field in the document, and filter by that. It's messy and you would have to trust that the front end enters correct info in the field.