将字段绑定到Javafx中的控制器

Question

I have built a scene in using scene builder and I have two textfields that are part of a UI, One for Flavor, one for Topping. In the controller I've annotated each textfield attribute with @FXML. My question is: how do I associate the fields in the ui to the attributes in the controller class?

The java code looks like:

@FXML
private TextField flavorValueField;
@FXML
private TextField toppingValueField;

In the ui, the fields exist in a scene, but really have nothing associated with them that identifies them. Do they need something? and It's not clear to me, how I assure the binding between the field in the UI and the field in the code occur in the way I want them to.

It's not enough to say, it just works. I want to understand how the code knows to bind one field in the UI to an attribute in the code. The UI fields are generic. There's no identifier or classifier that says, this one is flavor and that one is topping. If it just "works" how does the binding happen?

Answer 1

FXMLLoader checks for fx:id attributes in the fxml file. If there is field visible to FXMLLoader in the controller that matches the value of this attribute, FXMLLoader attempts to assign the object created for the element containing the attribute to the field using reflection.

Eg

<Button fx:id="foo"/> <!-- this is assigned to the foo field, if possible -->
<Button fx:id="bar"/> <!-- this is assigned to the bar field, if possible -->

@FXML
private Button bar;

@FXML
private Object foo;

Note that the values only become available when fxml is finished loading or in the initialize method, if it exists. In the initializer/constructor of the controller they still contain null .

Answer 2

You don't need to do anything more than what you did. It's just @FXML, it'll bind the field in UI with the controller variable. Make sure to bind the scene in UI with the controller in scene builder.