如何訪問隨機子女Firebase DataBase ..？

是否有任何可能的方式來產生從兒童的孩子的結果就像我在單個問題上尋找多個答案。如何訪問隨機子女Firebase DataBase ..？

"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" 
    } 
    },

隨機生成的節點。！想要做這樣的事情！

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();

它會使性能較慢我在尋找一些東西更快的使用！

尋找這樣的事情

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

來源

2017-03-17 Atif AbbAsi

您正在尋找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，雖然這將起作用，但我強烈建議您更改數據模型以使此類查詢更具可伸縮性。由於答案屬於問題，您應該對該層次結構進行建模。雖然你不應該搭配的問題和答案，你應該考慮下這個問題ID造型答案：

"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" : { 
    "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", 
    } 
    } 
}

通過這樣的結構，你可以得到Q1的答案有直接查找，而不是一個查詢（在每個增長列表中）：

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()); 
     } 
    } 
    ...

來源

2017-03-17 14:11:51

如何訪問隨機子女Firebase DataBase ..？

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