I want cumulative of production qty which I saved in key value ‘pqty’ in firebase?

I want cumulative of production qty in key ‘pqty’ property:

 DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
 DatabaseReference valuesRef = rootRef.child("alldata").child("pqty");
 ValueEventListener eventListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
    int sum = o;
    for(DataSnapshot ds : dataSnapshot.getChildren()) {
        int value = ds.getValue(Integer.class);
        sum = sum + value;

    }
    textview15.setText(String.valueOf(sum));
}

@Override
public void onCancelled(DatabaseError databaseError) {}
};

    valuesRef.addListenerForSingleValueEvent(eventListener);

I tried this and got output as 0. But I want output as 750.

I’m using sketch ware.

Answer

First of all, you are storing the “pqty” property in your database as a String and not as a number, which in my opinion is a really bad idea. If your data type is a number, then you should store it like that. Now, to get the desired sum, please use the following lines of code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference alldataRef = rootRef.child("alldata");
alldataRef.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DataSnapshot> task) {
        if (task.isSuccessful()) {
            int sum = 0;
            for (DataSnapshot ds : task.getResult().getChildren()) {
                String pqty = ds.child("pqty").getValue(String.class);
                sum += Integer.parseInt(pqty);
            }
            Log.d("TAG", "sum= " + sum);
            textview15.setText(String.valueOf(sum));
        } else {
            Log.d(TAG, task.getException().getMessage()); //Don't ignore potential errors!
        }
    }
});

According to your screenshot, the result in your logcat will be:

sum= 750

Things to notice:

• There’s no need for any “.child(“pqty”)” call in your “valuesRef” reference whatsoever, because you need to loop through the “DataSnapshot” object using a call to “.getChildren()” method and then get the value of “pqty” property.
• To be able to sum those values, you need to parse that String object into a number using Integer.parseInt(String s) method.
• There is no way you can get a String value from the database using “.getValue(Integer.class)”, as it will always yield an Exception. You need to get it as it’s actually stored.