Nsryjdtyk

I am creating an app in which points increases on button click and those points should be saved to firebase. I managed to save those data to firebase. But when I destroy my app and open it again the points value is showing same but after clicking button. It again starts from 0.

For example: every time on button click the points value increases to 10 points. Now when I completely destroy the app and open it again, the points value shows same, but when button clicked it again starts from initial condition.

Here is my code

    int amount = 0;



@Override

    protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main2);



button_claim.setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View v) {

            amount = amount + 100;





            textView_points.setText(String.valueOf(amount));

            databaseReference.setValue(textView_points.getText().toString());



        }

    });





}





@Override

    protected void onStart() {

    super.onStart();

    if (mAuth.getCurrentUser() == null) {

        finish();

        Intent main = new Intent(this,MainActivity.class);

        main.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

        startActivity(main);

    }



    databaseReference.addValueEventListener(new ValueEventListener() {

        @Override

        public void onDataChange(DataSnapshot dataSnapshot) {



            textView_points.setText(dataSnapshot.getValue(String.class));

            databaseReference.setValue(textView_points.getText().toString());

        }



        @Override

        public void onCancelled(DatabaseError databaseError) {



            Toast.makeText(Main2Activity.this,"error",Toast.LENGTH_LONG).show();

        }

    });







    }

Before destroying the app
see the image please, points increasing on button click before destroying the app and uploading to database
please see image 1

Opened app again(after closing) it is showing the same updated point
please see image 2

Now when i click claim it returns back to 100
please see image number 3

please help me on this problem, and i am a newbie
Thanks

This is how you set a value in your Firebase database:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();

rootRef.child("score").setValue(1);

Assuming that the your score field is of type Integer, to solve this, 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) {}

    });

}

For this, I recommend you definitely use transactions. You will avoid wrong results if users are trying to increase/decrease the score in the same time. So as a conclusion, call this method accordingly to your increase/decrease operation.

This is how you can read it:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();

DatabaseReference scoreRef = rootRef.child("score");

ValueEventListener eventListener = new ValueEventListener() {

    @Override

    public void onDataChange(DataSnapshot dataSnapshot) {

        Integer score = ds.getValue(Integer.class);

        Log.d("TAG", score + "");

    }



    @Override

    public void onCancelled(DatabaseError databaseError) {}

};

scoreRef.addListenerForSingleValueEvent(eventListener);

You need to first get the value of previous score and then add it with the current score and then update the final value in the firebase database.

question_score.child("score").addValueEventListener(new ValueEventListener() {

                        @Override

                        public void onDataChange(DataSnapshot dataSnapshot) {

                            String previousScore = dataSnapshot.getValue(String.class);

                            if (previousScore!=null){

                                int finalScore = Integer.parseInt(previousScore) + current_score;

                                question_score.child("score").setValue(String.valueOf(finalScore));

                            }

                        }



                        @Override

                        public void onCancelled(DatabaseError databaseError) {



                        }

                    });