Sending data back to the Main Activity in Android

Question

I have two activities: main activity and child activity.
When I press a button in the main activity, the child activity is launched.

Now I want to send some dat

Answer 1

Activity 1 uses startActivityForResult:

startActivityForResult(ActivityTwo, ActivityTwoRequestCode);

Activity 2 is launched and you can perform the operation, to close the Activity do this:

Intent output = new Intent();
output.putExtra(ActivityOne.Number1Code, num1);
output.putExtra(ActivityOne.Number2Code, num2);
setResult(RESULT_OK, output);
finish();

Activity 1 - returning from the previous activity will call onActivityResult:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == ActivityTwoRequestCode && resultCode == RESULT_OK && data != null) {
        num1 = data.getIntExtra(Number1Code);
        num2 = data.getIntExtra(Number2Code);
    }
}

UPDATE: Answer to Seenu69's comment, In activity two,

int result = Integer.parse(EditText1.getText().toString()) 
           + Integer.parse(EditText2.getText().toString());
output.putExtra(ActivityOne.KEY_RESULT, result);

Then in activity one,

int result = data.getExtra(KEY_RESULT);