Searching firebase if a value exists or not

Question

I have the following data structure in my firebase. I am implementing a coupon based system where you enter a code in dialogue box and it is searched across the database. So I have been trying to figure out this but I haven't found the perfect query that can search the code, if found, then get all the other child values too.

Below is the code that i have been trying with:

private void couponsearch() {
        final EditText taskEditText = new EditText(this);
        AlertDialog.Builder dialog = new AlertDialog.Builder(this)
                .setTitle("Akiba Yangu")
                .setMessage("Enter Akiba Code Here.")
                .setIcon(R.drawable.akyi)
                .setView(taskEditText).setPositiveButton("SAVE",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog,int id) {
                        String stringe = taskEditText.getText().toString();
                        DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
                        mDatabase.child("codes").orderByChild("code").equalTo(stringe).addValueEventListener(new ValueEventListener() {
                            @Override
                            public void onDataChange(DataSnapshot dataSnapshot) {
                                Coupons coo = dataSnapshot.getValue(Coupons.class);
                                String name = dataSnapshot.getKey();
                                int codez = coo.getValuee();
                                code.setText(name);
                                if(dataSnapshot != null  && dataSnapshot.getChildren().iterator().hasNext()){
                                    for(DataSnapshot ds : dataSnapshot.getChildren()) {
                                        codegotten();
                                    }
                                }else {
                                    nocode();
                                }

                                int val = coo.getValuee();
                                Akibasavings as = new Akibasavings();
                                String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();



                                System.out.println(val);
                                code.setText(name);
                                as.setName(name);
                                as.setAmount(val);

                                final Firebase ref = new Firebase("https://akiba-c9600.firebaseio.com/");
                                Firebase newRef = ref.child("Savings"+uid).push();
                                newRef.setValue(as);
                                sendNotification();
                            }
                            @Override
                            public void onCancelled(DatabaseError databaseError) {
                            }
                            public void onCancelled(FirebaseError firebaseError) {
                                //Username Does Not Exist
                            }
                        });
                    }
                });
        dialog.show();
    }

I would like to search the code, check if it is really there or not: if it is there I need to get all the other values too, i.e there are three nodes in every child. code, brand, value. After I have checked that the code exists, I would like to also get the other values associated with it. Regards

Answer 1

When you execute a query against the Firebase Database, there will potentially be multiple results. So the snapshot contains a list of those results. Even if there is only a single result, the snapshot will contain a list of one result.

Your onDataChange() needs to handle the fact that the snapshot contains a list of result by looping over DataSnapshot.getChildren():

mDatabase.child("codes").orderByChild("code").equalTo(stringe).addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
            Coupons coo = childSnapshot.getValue(Coupons.class);
              String name = childSnapshot.getKey();
              int codez = coo.getValuee();
              code.setText(name);
              ...
        }
    }

Answer 2

What you need is Query.

DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
Query mQuery = mDatabase.child("codes").orderByChild("code").equalTo(stringe);
mQuery.addListenerForSingleValueEvent(new ValueEventListener() {
    // use single value event listener to detach listener immediately after query
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        if (dataSnapshot.getValue() != null) {
            // code exists, cast your data to relevant object
            // note that if multiple entries exists, you need to loop through them
        } else {
            // code does not exists
        }
     }
});

Read the official document here.

Note that you must remember to index your firebase properly! Query on firebase is not the same as local database query. If you do not index your firebase, the query will download everything under the codes section into user phone, before doing the search locally on user phone. This will consume high bandwidth and memory. Learn more about index here. Read about my personal issue with index previously here.

Answer 3

To achieve this, i recomand you change the structure of your database a little bit by adding a new node named coupons. Your database should look like this:

Firebase-root
    --- coupons
          TTUUPP: true
          KKLLOO: true

To check if a coupon exists in your database, just add a listener on the new created node and use exists() method. This is a coomon practice within Firebase named denormalization and is for simplify and reduce query and bandwith. This what you need.