Firebase DatabaseReference按指定值过滤 [英] Firebase DatabaseReference filter by specified values

问题描述

让我们假设我具有以下firebase JSON结构:

Lets suppose I have this firebase JSON structure:

我需要获得所有归因于"from"等于"this"的问题.

And I need to get all the questions which have the atribute "from" equal to "this".

我知道我可以使用Volley发出StringRequest并从questions.json中获取所有值.然后，在客户端，我可以遍历响应并删除那些没有正确属性的响应，但这仅在我有几个问题的情况下有效.如果我有数百万个问题，则需要遍历数百万个问题.

I know that I can use Volley to make a StringRequest and GET all values from my questions.json. Then, in the client side I could iterate over the response and remove the ones which don't have the correct atribute, but this would only work if I have a few questions. If I have millions of questions I would need to iterate over those millions of questions.

有什么办法可以对请求添加过滤器，以仅获取具有所选属性的问题? (例如:从这里的==搜索searchquestions.json)

Is there any way I could put a filter on my request to get only the question with an attribute of my choice? (Ex: search questions.json where from == this)

推荐答案

如果在您的情况下可能有用，请尝试

Try this if may be useful in your scenario

 DatabaseReference reference = FirebaseDatabase.getInstance().getReference();

    Query query = reference.child("questions").orderByChild("from").equalTo("this");
    query.addListenerForSingleValueEvent(new ValueEventListener() { 
        @Override 
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.exists()) {

                for (DataSnapshot issue : dataSnapshot.getChildren()) {
                // do with your result
                } 
            } 
        } 

        @Override 
        public void onCancelled(DatabaseError databaseError) {

        } 
    }); 

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