title: method executing multiple times instead of just one
body: <pre><code>Query ref = mDatabaseReference.child("Messages")
              .child(MessageRecieverId).child(MessageSenderId).orderByChild("Seen").equalTo(false);
      ref.addValueEventListener(new ValueEventListener() {
          @Override
          public void onDataChange(DataSnapshot dataSnapshot) {
              long count = 0;
              for(DataSnapshot ds : dataSnapshot.getChildren()) {
                  count = dataSnapshot.getChildrenCount();
  
                  MainData helper = new MainData(getApplicationContext()); //Change the name to your Helper Class name
                  SQLiteDatabase db = helper.getWritableDatabase();
                  String newId = "MyData";
                  Cursor data = helper.getData();
                  long newDatar = 0;
                  long newDatat = 0;
                  while(data.moveToNext()){
                      newId = data.getString(data.getColumnIndex("Data"));
                      newDatar = data.getInt(data.getColumnIndex("TotalMessagesRecieved"));
                      newDatat = data.getInt(data.getColumnIndex("TotalMessages"));
                  }
                  ContentValues contentValues = new ContentValues();
                  contentValues.put(KEY_DATA, newId);
                  contentValues.put(KEY_TOTAL_MESSAGES_RECIEVED, (newDatar+count));
                  contentValues.put(KEY_TOTAL_MESSAGES, (newDatat+count));//Change the value of newData(which is actually your old value) by incrementing
                  long returnVariable = db.update(TABLE_MAIN_DATA, contentValues, null, null);
  
                  if(returnVariable == -1){
                      Toast.makeText(getApplication(),"Nope", Toast.LENGTH_LONG).show();
                      //-1 means there was an error updating the values
                  }
                  else{
                      Toast.makeText(getApplication(),"r", Toast.LENGTH_SHORT).show();
                  }
              }
              Log.d("CMONNN", String.valueOf(count)); //Will print the number of seen messages
          }
  
          @Override
          public void onCancelled(@NonNull DatabaseError databaseError) {
              Log.d("CMONNN", databaseError.getMessage()); //Don't ignore errors!
          }
      });
  </code></pre>
  
  <p>The problem with this is the first time i open the activity and if there is one child to be added to the table in sqlite it adds normally without any problem and then i close the activity and i open it again and it adds the child twice even if there is just one and if i close and open it again it adds thrice instead of one and it just goes on... So why is this behavious and how can i change it to executing just once like the first time i open the activity... And i cannot use valueforsingleevent as i need to listen to listener when im inside the activity every second... and the removelistener too didnt work while closing the activity... So someone please help me out</p>