java - FXMLLoader how to access the components by FXID?

Question

I'm trying to figure out how to work with JavaFx. I built the application interface in Scene Builder. But I can not get access to the component, since all loaded into the Parent.

Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

If I change "Parent" on "Pane" I can get access to the getChildren(), but it is not clear how to get control if i know fx:id...

The question is even simpler. I added Label or TextField in Scene Builder. How do I change it's text from the code if I know the fx:id?

I am in despair.

Answer 1

You should create a controller class for your FXML document, in which you can perform any functionality you need to perform involving the UI components. You can annotate fields in that class with @FXML and they will be populated by the FXMLLoader, matching the fx:id attribute to the field name.

Work through the tutorial for more details, and have a look at the Introduction to FXML documentation.

Simple example:

Sample.fxml:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.layout.VBox?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.Button?>

<VBox xmlns:fx="http://javafx.com/fxml/1" fx:controller="SampleController">
    <Label fx:id="countLabel"/>
    <Button fx:id="incrementButton" text="Increment" onAction="#increment"/>
</VBox>

SampleController.java:

import javafx.fxml.FXML;
import javafx.scene.control.Label;


public class SampleController {

    private int count = 0 ;

    @FXML
    private Label countLabel ;

    @FXML
    private void increment() {
        count++;
        countLabel.setText("Count: "+count);
    }
}

SampleMain.java:

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class SampleMain extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception {
        Scene scene = new Scene(FXMLLoader.load(getClass().getResource("Sample.fxml")), 250, 75);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}