Question

是否有任何可能的方法来生成孩子的孩子的结果喜欢我在单个问题上寻找多个答案。！

"questions" : {
    "Q1(Random ID )" : {
      "description" : "Deail of Question",
      "idQuestion" : "Q1",
      "time" : "17 Mar 2017 16:18:12",
      "title" : "Title Of Question",
      "user_id" : "bXCeW6jfidbHuMCCCMkDGWcGZRS2"
    },
{
  "Answer" : {
    "81d19e85-8c6c-4824-9fb1-61a7cd316e32" : {
      "dateTime" : "17 Mar 2017 16:22:17",
      "Answer" : "Answer",
      "ProfessorId" : "da587c89-f001-43f2-984d-e6dbac491acc",
      "questionId" : "Q1"
    },
    "e2ec0556-4420-4d2f-b346-0b5cebeb1ebe" : {
      "dateTime" : "17 Mar 2017 16:55:27",
      "Answer" : "Answer 2 on Question 1",
      "answerId" : "0d20d6df-907d-4133-be53-ca6acf6c2ad1",
      "questionId" : "Q1"
    }
  },

随机生成的节点。！我想做这样的事情。！

mdatabaseReference.child("Answer").child(* Here Im Using "*" Like we used to do in SQl to get all data I knw its not a SQL but its just for conecpt).equalTo(QID).addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                if (Answer_List.size() > 0)
                    Answer_List.clear();


                for (DataSnapshot postsnapshot : dataSnapshot.getChildren()) {

而不是使用postSnapshot.getKey().equals("QID")

    if(postSnapshot.getKey().equals("QID"))  
 Answertext = postSnapshot.getValue().toString();

这会让性能变得更慢，我正在寻找更快的东西。！

寻找类似的东西

 mdatabaseReference.child("Answer").child("*").getKey().equals(QID).addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

Answer 1

您正在寻找Firebase Database queries。

mdatabaseReference
  .child("Answer")
  .orderByChild("questionId")
  .equalTo("Q1")
  .addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
      for (DataSnapshot answerSnapshot: dataSnapshot.getChildren()) {
        System.out.println(answerSnapshot.child("Answer").getValue());
      }
    }
    ...

但是，虽然这样可行，但我强烈建议您更改数据模型，以使此类查询更具可扩展性。由于答案属于问题，因此您应该对该层次结构建模。虽然不应该混合问题和答案，但应考虑在问题ID下对答案进行建模：

"questions" : {
    "Q1(Random ID )" : {
      "description" : "Deail of Question",
      "idQuestion" : "Q1",
      "time" : "17 Mar 2017 16:18:12",
      "title" : "Title Of Question",
      "user_id" : "bXCeW6jfidbHuMCCCMkDGWcGZRS2"
    },
}
"Answer" : {
  "Q1": {
    "81d19e85-8c6c-4824-9fb1-61a7cd316e32" : {
      "dateTime" : "17 Mar 2017 16:22:17",
      "Answer" : "Answer",
      "ProfessorId" : "da587c89-f001-43f2-984d-e6dbac491acc",
    },
    "e2ec0556-4420-4d2f-b346-0b5cebeb1ebe" : {
      "dateTime" : "17 Mar 2017 16:55:27",
      "Answer" : "Answer 2 on Question 1",
      "answerId" : "0d20d6df-907d-4133-be53-ca6acf6c2ad1",
    }
  }
}

通过这种结构，您可以通过直接查找而不是查询（在每个增长列表中）获得Q1的答案：

mdatabaseReference
  .child("Answer")
  .child("Q1")
  .addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
      for (DataSnapshot answerSnapshot: dataSnapshot.getChildren()) {
        System.out.println(answerSnapshot.child("Answer").getValue());
      }
    }
    ...

如何访问随机子Firebase数据库..？

1 个答案: