CODEWITHSUNDEEP
javaandroidfirebasefirebase-realtime-database
mark_test
mark_test

Reputation: 141

How to get value of Child of childs from firebase in java

Data structure

From this I want take the value of email from mailID and subject, title from mailText.i'm able to access the value of single child but when it show null with when try get with all three.

Following code working for single child:

DatabaseReference databaseRef = database.getReference("/");
    databaseRef.addValueEventListener(new ValueEventListener() {
                 public void onDataChange(DataSnapshot dataSnapshot) {
                    ArrayList<String> email = new ArrayList();
                     for (DataSnapshot sd: dataSnapshot.getChildren()) {
                         String emailStr = sd.child("email").getValue(String.class);
                         email.add(emailStr);
                         System.out.println(email);
                         }
                     latch.countDown();
                     }

Above code gives me array contain the all email like that i want to take value of email,title and subject.

Upvotes: 0

Views: 1502

Answers (2)

Alex Mamo
Alex Mamo

Reputation: 1

Assuming that the new node is a direct child of your Firebase root, to achieve what you have explained in your comments, please use the following lines of code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference newRef = rootRef.child("new");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.child("mailID").getChildren()) {
            String email = ds.child("email").getValue(String.class);
            String name = ds.child("name").getValue(String.class);
            Log.d("TAG", email + " / " + name);
        }
        for(DataSnapshot ds : dataSnapshot.child("mailText").getChildren()) {
            String title = ds.child("title").getValue(String.class);
            String subject = ds.child("subject").getValue(String.class);
            Log.d("TAG", title + " / " + subject);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
newRef.addListenerForSingleValueEvent(valueEventListener);

As you see, you need to attach a listener one step higher in your tree hierarchy and to loop throught the children using getChildren() method twice.

Upvotes: 1

Peter Haddad
Peter Haddad

Reputation: 80952

You need to change the database structure(there is no join in firebase), to be able to query and get the required data:

new
  mailId
     email: [email protected]
     name:userx
     title: test title
     Body: test body

Then you will be able to retrieve the required data for the user.

You can also use Queries to be able to get the related data, example:

DatabaseReference ref=FirebaseDatabase.getInstance().getReference().child("new");
ref.orderByChild("email").equalTo("[email protected]");

Upvotes: 0

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