Servis-Rhino 4211B Guia do Utilizador descarregar pdf (Página 258)

The fx:id attribute

Most nodes can have an "fx:id". This attribute names a Java variable of the same type of the

node. When the FXML is parsed, the variable will be updated to contain the reference to the node.

For example, if we define a label in FXML as:

then in the corresponding Java controller class:

@FXML

private Label myLabel;

The variable with the same name as the "fx:id" will be bound to that instance of the node.

When an fx:id attribute is found, we can think of this as creating an FXML named variable with

the value of the fx:id referencing the element to which it is attached. In other elements we can

refer to the element with the fx:id using the "$<name>" syntax.

We can also use an additional syntax that looks like "${<name>.<property>}" to dynamically

have an element's property bound to another elements property.

The fx:root element

The fx:root element is used to declare that the root element will NOT be created but rather will

be set by a call to to setRoot() prior to the load() method being called.

A Controller class

A controller class fulfills the controller part of the Model-View-Controller contract. An FXML

described application can name a controller class using the fx:controller attribute.

A method called "initialize()" can/should be implemented in the controller and will be called

to initialize an variables or data.

For example:

@FXML

private void initialize() {

// Do some initialization ...

}

The controller class can include variables that are injected/mapped to the fx:id references for

FXML elements. For example, if we define:

then in the controller class, we can specify:

@FXML

private TextField myText;

and when the Controller is instantiated, the "myText" variable will be automatically set to be a

referenced to the corresponding JavaFX TextField object.

For JavaFX widgets that can emit events, we can define functions within the controller class that

can be invoked to process such events.

For example:

@FXML

private void myHandler(ActionEvent event) {

// do something

}

And in the FXML, we can map the widget to this function using:

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Servis-Rhino 4211B Guia do Utilizador Página 258