Why I'm getting javafx.fxml.LoadException even the path of the fxml file is correct

Question

I get

javafx.fxml.LoadException:

When I\'m loading and fxml file using following line of code.

AnchorPane

Answer 1

I was about to enter a different question as remarked by @James_D for my comment because Until I Read the first line of the FXML on this question, I had thought that I had a different problem.

For my sins, I reduced the challenge to a simple example of a single controller and two FXML files. One worked and the second fail/failed.

The starting point is the Netbeans sample "[Click me!]" sample. The code is pasted below. And, first a solution.

As preamble, let me say that it seems that everyone has been blaming the Java controller for these load errors. I had a bunch of errors like this on a project a couple of years ago. We exhausted "controller" debugging and eventually pressed-forward by re-building the FXML screens with ScendBuilder. I didn't have time to investigate further then.

Last week I perfectly working FXML screen started failing to load because we moved it to a runtime directory (previously it was in the JAR resources area).

KLUNK!

After 3 or 4 days tweaking that and this, I made a comment here on my error:

• unknown path: 7
• Javafx fxml LoadException: Error resolving onAction='#handleButtonAction', either the event handler is not in the Namespace or there is an error in the script.

On only the "simple.fxml" file, but not the "Scene.fxml" file. The file "simple.fxml" is reduced from the app FXML file that initially gave the problem. There were too many variables on that original file, so chop-chop-chop to match the canned demo.

When you use ONLY this:

xmlns:fx="http://javafx.com/fxml"

FXML load-s from files on disk under in your application folder work just like you want them to (well, like I want, anyway). Looking at the FXML above it is using a more 'fragile' namespace, viz.

Queston's original FXML:

By using diff, I slowly morphed "simple.fxml" to be as close as possible to "Scene.fxml", and "simple" just keeps failing to load. Please note; always using the same controller

Loading FXML with other metadata has not worked consistently an FXML file was moved. I don't have an explanation as to how this is so.

The FXML is kept in a directory called "test/resources/fxml/simple.fxml" for example. When I was building with both files in the project JAR, the 'same' FXML in both cases loaded and worked as expected. To me there's something un-said about aspects of the file load precess. Again for me, this is undesirable because the KEY value of a external scene definition would be interchange.

These kind of bear traps in XML mark-up that are (apparently) not picked up by development tools like SceneBuilder or the FXMLLoader() are barriers to progress on live projects that don't have slack to investigate esoteric weirdness like this.

This is witnessed by our previous project experience -- I was easier to re-edit a complex screen with SceneBuilder as a whole than track down load problems like this one. The call to action is: Diagnostics on FXML load -- an FXML Lint would be almost a requirement.

---

Controller, SimpleController.java:

  package ex.view.views;

  import java.net.URL;
  import java.util.ResourceBundle;
  import javafx.event.ActionEvent;
  import javafx.fxml.FXML;
  import javafx.fxml.Initializable;
  import javafx.scene.control.Label;

  public class SimpleController implements Initializable {

      @FXML
      private Label label;

      @FXML
      private void handleButtonAction(ActionEvent event) {
          System.out.println("You clicked me!");
          label.setText("Hello World!");
      }

      @Override
      public void initialize(URL url, ResourceBundle rb) {
          // TODO
      }    
  }

The failing FXML started life as one of the Maven archetypes (I think) and that file worked fine until I moved the FXML files to a folder and loaded them from a InputStream.

I have formatted the AnchorPane markup on multiple lines for readability.

simple.fxml:

The working FXML mark-up is from the Netbeans 8.1 samples.

Scene.fxml: