Error Expected a value ot type '(() => void)?', but got one of type '+Future<dynamic>'

I am trying to save data to firestore using flutter, the tricky part is my textformfield sets the data as null or "" because it sets the data as the form page loads in and then I get the error : Expected a value ot type '(() => void)?', but got one of type '+Future'

Below is my code:

  final barcode = TextEditingController();
  final price = TextEditingController();//these are from my textformfield
  final stock = TextEditingController();
  final color = TextEditingController();

  addData() async {
    // ASYNC HERE
    Map<String, dynamic> theData = {
      "Color": color.text,
      "Price": price.text,
      "Stock": stock.text,
    };
    CollectionReference collectionReference = Firestore.instance.collection("products");
    await collectionReference.doc(barcode.text).set(theData);
  }

I think the answer is probably something to do with a future function somewhere.

Below is where I call addData:

  FloatingActionButton.extended(
    onPressed: addData(),
    label: Text('Done'),
    icon: Icon(Icons.add),
    backgroundColor: Colors.blue,
  ),