How do I sum up value from onactivityresult

See more:

Java

Android

I have a listview in Activity A. I want to sum up the total amount which are return from Activity B to Activity A, but I have no idea on how to add them up.

@Override
  public void onActivityResult(int requestCode, int resultCode, Intent data) { // receive from Activity B and populate ListView A
      if (resultCode == RESULT_OK) {
          if (requestCode == PROJECT_REQUEST_CODE) {
              ReceiveAmount = data.getStringExtra("amount");
             Toast.makeText(getApplication(),"Total Amount is"+ReceiveAmount,LENGTH_SHORT).show();
              }
          }
      }
  }

Assume in Activity B I return amount 5, then I go to Activity B again and return value 10. I want the toast display value 15 instead of always 5.


Edited

public void onActivityResult(int requestCode, int resultCode, Intent data) { // receive from Activity B and populate ListView A
     if (resultCode == RESULT_OK) {
         if (requestCode == PROJECT_REQUEST_CODE) {
             double sum = 0;
             ReceiveAmount = data.getStringExtra("amount");
            sum = + ReceiveAmount;
            Toast.makeText(getApplication(),"Total Amount is"+sum,LENGTH_SHORT).show();
             }
         }
     }
 }

What I have tried:

Google but no answer found. Thanks