CODEWITHSUNDEEP
javaandroidfirebasefirebase-realtime-database
tarun14110
tarun14110

Reputation: 990

Retrieve data from Firebase for multiple child nodes

I am working on app where I want to show the data only of the users whose contact numbers are saved in the phone. So, I retrieved a list of contact numbers contactList. Now, I want to get all the contactList user's post from Firebase. Is there any way I can ask the Firebase for only those nodes in my contactList. One Way is to retrieve all users and then get relevant users from that (like I did below). Is there any better way to do so ?

Users: { 
            7828272892 : {
                 name: xyz, 
                 gender: male,
                 phoneNo: 7828272892
                 Posts: {
                     SomeKey1: {
                         content: "This is post 1", Var2: "kkk"} }},
            7924272894 : {name: abc, gender: male, phoneNo: 7924272894} 
        }

Code:

 databaseReference.child("Users").addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {
                List<Post> allItems = new ArrayList<Post>();
                for (DataSnapshot postSnapshot: snapshot.getChildren()) {
                 if (contactList.contains(postSnapshot.child("phoneNo").getValue())) {
                      // retrieve posts
                  }
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });

Upvotes: 1

Views: 2603

Answers (2)

user4571931
user4571931

Reputation:

Try this code to read multiple nodes data..

 mFirebaseInstance = FirebaseDatabase.getInstance();
    mDatabase = mFirebaseInstance.getReference("usersDb/UserTable");
    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            mUserList.clear();
            for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                User user = dataSnapshot1.getValue(User.class);
                mUserList.add(user); // add all data into list.
            }
            }


        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

Upvotes: 1

Alex Mamo
Alex Mamo

Reputation: 138824

Is there any way I can ask the firebase for only those nodes in my contactList?

Yes, the way in which you already do this.

Is there any better way to do so?

The way in which you do this is a common practice used in Firebase. You query the database and check is the data already exists in the list, in your case in the contactList. If the list contains that phoneNo then you can retrieve the posts.

Upvotes: 1

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