MainActivity.java

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (resultCode == RESULT_OK && data != null) {
        switch (requestCode) {
            case 10:
                int intFound = getNumberFromResult(data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS));
                if (intFound != -1) {
                    FIRST_NUMBER = intFound;
                    firstNumTextView.setText(intFound);
                } else {
                    Toast.makeText(getApplicationContext(), "Sorry, I didn't catch that! Please try again", Toast.LENGTH_LONG).show();
                }
                break;
            case 20:
                intFound = getNumberFromResult(data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS));
                if (intFound != -1) {
                    SECOND_NUMBER = intFound;
                    secondNumTextView.setText(intFound);
                } else {
                    Toast.makeText(getApplicationContext(), "Sorry, I didn't catch that! Please try again", Toast.LENGTH_LONG).show();
                }
                break;
            case 30:
                char operatorFound = getOperatorFromResult(data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS));
                if (operatorFound != '0') {
                    OPERATOR = operatorFound;
                    operatorTextView.setText(operatorFound);
                } else {
                    Toast.makeText(getApplicationContext(), "Sorry, I didn't catch that! Please try again", Toast.LENGTH_LONG).show();
                }
        }
    } else {
        Toast.makeText(getApplicationContext(), "Failed to recognize speech!", Toast.LENGTH_LONG).show();
    }
}