JavaFX: LoadException resolving onAction for event handler of a button

Question

I am new to JavaFX. Trying to follow a tutorial to generate a scene and associate eventhandler with a button.

I created a Main.FXML and edited in SceneBuilder. Since I added SceneBuilder's path in my IDE, it is able to detect my main controller. I wrote a function to generate random number.

public class MainController {

    public static void generateRandom(ActionEvent event) {
        Random rand = new Random();
        int myrand = rand.nextInt(500) + 1;
        System.out.print(Integer.toString(myrand));
    }
}

In scenebuilder, it detects this method in controller which can be easily added as eventhandler for OnAction of the button. Main.FXML is updated after the operations.

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

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


<AnchorPane prefHeight="300" prefWidth="500" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8.0.111" fx:controller="application.MainController">
   <children>
      <Button layoutX="204.0" layoutY="204.0" mnemonicParsing="false" onAction="#generateRandom" text="Button" />
      <Label layoutX="138.0" layoutY="36.0" prefHeight="144.0" prefWidth="210.0" />
   </children>
</AnchorPane>

My main application class is as below:

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) throws IOException {
        Parent root = FXMLLoader.load(getClass().getResource("/application/Main.fxml"));
        Scene scene = new Scene(root,400,400);
        scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
        primaryStage.setTitle("My Title");
        primaryStage.setScene(scene);
        primaryStage.show();

    }

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

When I run the app, I got error:

javafx.fxml.LoadException: Error resolving onAction='#generateRandom', either the event handler is not in the Namespace or there is an error in the script. /C:/Users/Oscar/Workspace/Sunoco/bin/application/Main.fxml:10

Error resolving “onAction” while loading FXML suggests it may have to do with wrong import for ActionEvent which is not the case. Plus everything is set up automatically using SceneBuilder and Eclipse. So why am I getting this error?

score 3 · Accepted Answer · answered Mar 01 '17 at 05:21

3

I think the problem will be solved if you use an @FXML annotation on the eventMethod. Besides, try not to make methods static in the controller, as it may be confusing/misleading. If you need that method to be accesible from elsewhere, consider declaring it in a separate (utility like) class.

answered Mar 01 '17 at 05:21

n247s

1,898
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Looks like `static` is causing problem. After I took it out it worked without `@FXML` annotation. – ddd Mar 01 '17 at 05:45
I used skeletal constructor code from SceneBuilder. This had "internal" functions, so the .jfx file couldn't find these functions. – james.sw.clark Mar 22 '18 at 11:39

JavaFX: LoadException resolving onAction for event handler of a button

1 Answers1