Error in reading the Firebase: from firebase value to child

Question

I have created an event handler for the onClick button. When I click on the button, I want to transfer a pre-recorded number in the database to the price section.

My problem is that: when I click on the button and want to pass the value "pricecode" recorded in the database to "price". But it is mandatory that the pricecode is pre-recorded in the database.

String price = String.valueOf(db.child("User").child("pricecode"));

and instead of the value "1000", it writes a reference to the key there. Read more in the screenshot.

public void onClickB1 (View view)

    {
        DatabaseReference db = FirebaseDatabase.getInstance().getReference();
        String id = mDataBase.getKey();
        String name = String.valueOf(textB1.getText());

        String price = String.valueOf(db.child("User").child("pricecode")); // PROBLEM

        User newUser = new User(id,name,price);
        //mDataBase.push().setValue(newUser);

        if (!TextUtils.isEmpty(name))
        {
            mDataBase.push().setValue(newUser);
        }
        else
        {
            Toast.makeText(this,"empty text",Toast.LENGTH_LONG).show();
        }
    }

Answer 1

String price = String.valueOf(db.child("User").child("pricecode")); and instead of the value "1000", it writes a reference to the key there.

That's the expected behavior since the following operation:

String price = String.valueOf(db.child("User").child("pricecode"))

Does not store in the price variable the actual value (1000) of the pricecode field. The code inside the valueOf() method is a reference, so when you're passing that reference to the valueOf() method, you get:

https://testkornze...

So there is no way you can read a value of a particular field that exists in the Realtime Database without attaching a listener. I answered earlier a question of yours on how to read the value of pricecode. So to be able to use the value of pricecode, all operations that need data from the database should be added inside the onComplete() method.

Answer 2

As Alex explained this code merely builds a reference to a path in the database, but doesn't actually read the value from that path:

db.child("User").child("pricecode")

To read the value, you either need to call addListenerForSingleValueEvent , or call get on the reference, as shown int he Firebase documentation on reading data once. Based on that:

db.child("User").child("pricecode").get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DataSnapshot> task) {
        if (!task.isSuccessful()) {
            Log.e("firebase", "Error getting data", task.getException());
        }
        else {
            DataSnapshot snapshot = task.getResult()l

            String price = String.valueOf(snapshot.getValue());

            User newUser = new User(id,name,price);
            //mDataBase.push().setValue(newUser);

            if (!TextUtils.isEmpty(name))
            {
                mDataBase.push().setValue(newUser);
            }
            else
            {
                Toast.makeText(this,"empty text",Toast.LENGTH_LONG).show();
            }
        }
    }
});