Error resolving "onAction" while loading FXML

Question

I'm having some issues getting a simple hello world application to run. It is throwing the following error:

Exception in Application start method
Exception in thread "main" java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$152(LauncherImpl.java:182)
    at com.sun.javafx.application.LauncherImpl$$Lambda$2/1329552164.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException: Error resolving onAction='#printHello', either the event handler is not in the Namespace or there is an error in the script.
/home/willi/java/IdeaProjects/JavaFXApp/out/production/JavaFXApp/sample/sample.fxml:23

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
    at javafx.fxml.FXMLLoader.access$100(FXMLLoader.java:104)
    at javafx.fxml.FXMLLoader$Element.processEventHandlerAttributes(FXMLLoader.java:606)
    at javafx.fxml.FXMLLoader$ValueElement.processEndElement(FXMLLoader.java:766)
    at javafx.fxml.FXMLLoader.processEndElement(FXMLLoader.java:2827)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2536)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2445)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3218)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3179)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3152)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3128)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3108)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3101)
    at sample.Main.start(Main.java:13)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
    at com.sun.javafx.application.LauncherImpl$$Lambda$57/2085742749.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl$$Lambda$52/738441956.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
    at com.sun.javafx.application.PlatformImpl$$Lambda$55/689939224.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
    at com.sun.javafx.application.PlatformImpl$$Lambda$53/1382865734.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication.lambda$null$48(GtkApplication.java:139)
    at com.sun.glass.ui.gtk.GtkApplication$$Lambda$43/704249306.run(Unknown Source)
    ... 1 more

My Controller.java file has the methods printHello and printWorld defined in them, and I would like to call them when I press their corresponding buttons. The code is as follows: package sample;

import javafx.fxml.FXML;
import javafx.scene.control.Button;
import java.awt.event.ActionEvent;

public class Controller {

    @FXML
    private Button helloButton;

    @FXML
    private Button worldButton;

    @FXML
    private void printHello(ActionEvent e){
        System.out.println("Hello");
    }

    @FXML
    private void printWorld(ActionEvent f){
        System.out.println("World");
    }
}

` In my fxml file, I have two buttons defined. Their code is as follows:

<Button fx:id="helloButton" layoutX="46.0" layoutY="87.0" mnemonicParsing="false" onAction="#printHello" text="Hello" />

<Button fx:id="worldButton" layoutX="97.0" layoutY="87.0" mnemonicParsing="false" onAction="#printWorld" text="World" />

Why is my code throwing this error?

Sorry in advance for the terrible formatting, this is my first time posting.

This should work. Can you make sure that you have provided the correct controller class name in the fxml? Or, post the complete fxml here, along with the package names for Controller. — ItachiUchiha, Apr 08 '15 at 05:37

score 73 · Accepted Answer · answered Apr 08 '15 at 05:42

73

You have imported wrong ActionEvent in controller class.

import java.awt.event.ActionEvent;

Correct it to

import javafx.event.ActionEvent;

answered Apr 08 '15 at 05:42

Uluk Biy

48,655
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Any suggestions on how to proceed if I have the correct import but the issue is still there? – Riley Fitzpatrick Feb 03 '19 at 05:47
This solved my issue. Netbeans imported the wrong ActionEvent class. – Javier Reséndiz Jun 12 '20 at 04:31
@RileyFitzpatrick I would recommend to check if that method exists in the controller. – yamanidev Jun 29 '21 at 17:19

Error resolving "onAction" while loading FXML

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