[FIXED] Android studio value increment in Firebase

Issue

Can anyone teach me how to update my Firebase value when I click on my Android Studio App? There is no need to retrieve and display the data. Just an incremental value in my Realtime Database. For example, the Firebase counter value is 0 now, how I can increase the counter value in Firebase when I click on a button? I have tried using the code below, but it is not working.

import com.firebase.client.Firebase;

public class Voting extends AppCompatActivity {
private Button msendData;
int counter;
    private  Firebase mRef;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_voting);
        Firebase.setAndroidContext(this);

        mRef = new Firebase("https://lollol.firebaseio.com/");
        msendData = (Button) findViewById(R.id.votethis);
        msendData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Firebase mRefChild = mRef.child("Booth A");
                mRefChild.setValue(counter++);
            }

Solution

Edit: 20222608

Actually, there is a really simple solution nowadays in which we can increment a field in the Realtime Database which is:

scoreRef.setValue(ServerValue.increment(1));

And to decrement a value, simply pass a negative number:

scoreRef.setValue(ServerValue.increment(-1));

---

In order to increment a value in a Firebase database, first of all, you need to retrieve that value. There is no way to increment a value without knowing it. To achieve this, I definitely recommend you to use Firebase Transaction.

Let's take an example. Let's assume we want to increment a counter. In order to achieve this, please use the following code to set the default value of the counter.

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
rootRef.child("score").setValue(1);

Assuming that the score field is of type Integer, to use transactions, please use the following method:

public static void setScore(String operation) {
    DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
    DatabaseReference scoreRef = rootRef.child("score");
    scoreRef.runTransaction(new Transaction.Handler() {
        @Override
        public Transaction.Result doTransaction(MutableData mutableData) {
            Integer score = mutableData.getValue(Integer.class);
            if (score == null) {
                return Transaction.success(mutableData);
            }

            if (operation.equals("increaseScore")) {
                mutableData.setValue(score + 1);
            } else if (operation.equals("decreaseScore")){
                mutableData.setValue(score - 1);
            }

            return Transaction.success(mutableData);
        }

        @Override
        public void onComplete(DatabaseError databaseError, boolean b, DataSnapshot dataSnapshot) {}
    });
}

Using transactions, you will avoid inconsistent results if users are trying to increase/decrease the score at the same time. So as a conclusion, call this method accordingly to your increase/decrease operation.

If you want to read the score, please use the following code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference scoreRef = rootRef.child("score");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Integer score = dataSnapshot.getValue(Integer.class);
        Log.d("TAG", "score: " + score);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
scoreRef.addListenerForSingleValueEvent(eventListener);

Answered By - Alex Mamo
Answer Checked By - Mildred Charles (JavaFixing Admin)