如何在 android 工作室中从 firebase 检索多个子节点

Question

I am trying to get data relating to a specific user in the database returned to a users screen in android studio. The data in firebase takes a format like so:

"studentNumber" : {
        "1234567" : {
            "CS320" :{
                "Lab 1" : "80%",
                "Lab 2" : "90%"
            },
            "CS255" :{
                "Lab 1" :"30%"
            }
        },
        "6234567" : {
            "CS320" :{
                "Lab 1" : "70%",
                "Lab 2" : "100%"
            },

and so on like that.

I am trying to get all data/child nodes ie all modules, subsequent labs and subsequent grades relating to one singular student returned to their screen in android studio, however, so far I have only been able to get the data returning to the console in android studio instead of the application screen.

This is the code I'm using to get the data.

  databaseReference = FirebaseDatabase.getInstance().getReference("User").child("0000");
  databaseReference.addValueEventListener(new ValueEventListener() {
     @Override
     public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        Log.v("E_Value","Data :" +dataSnapshot.getValue());
           }
   }

Any help would be great thanks.

Answer 1

I didn't test the code, however the outline should look like this.

You should be fetching one key and call a function to obtain the value and the subsequent nodes related to it and their values.

 databaseReference = FirebaseDatabase.getInstance().getReference("User").child("0000");
  databaseReference.addValueEventListener(new ValueEventListener() {
     @Override
     public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        for(DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()){
             String studentKey = dataSnapshot1.getKey();
             fetchDetails(studentKey);
        }
     }
   }

   public void fetchDetails(String studentKey) {
       DatabaseReference ref = FirebaseDatabase.getInstance().getReference("User").child("0000").child(studentKey);
       ref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for(DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()){
             String courseKey = dataSnapshot1.getKey(); //this should print CS320
             fetchDetailsOfCourse(courseKey);
        }
        }
     }
   }

   public void fetchDetailsOfCourse(String courseKey) {

      System.out.System.out.println("Course key: " + courseKey);
       DatabaseReference ref = FirebaseDatabase.getInstance().getReference("User").child("0000").child(studentKey).child(courseKey);
       ref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            String lab1 = dataSnapshot.child("lab1").getValue(String.class);
            String lab2 = dataSnapshot.child("lab2").getValue(String.class);

            System.out.println("Lab1 value: " + lab1); //this should get the values for lab1
            System.out.println("Lab2 value: " + lab2); //this should get the values for lab2

        }
        }
     }
   }