javafx8 FXMLLoader returns null - javafx-8

Question

I believe the only thing different with this is the version of SceneBuilder is 8.3 and I am using TreeTableView and TreeTableColumn with Oracle Java 8
Here is the fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.TreeTableColumn?>
<?import javafx.scene.control.TreeTableView?>
<TreeTableView maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" minHeight="1" minWidth="1" prefHeight="400.0" prefWidth="600.0" showRoot="false" stylesheets="#org/cornova/AudioExplorer.css" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1" fx:controller="org.cornova.AudioExplorerController">
<columns>
<TreeTableColumn fx:id="mixerName" editable="false" maxWidth="6000.0" minWidth="100.0" prefWidth="-1.0" text="Mixers" />
<TreeTableColumn fx:id="lineNames" maxWidth="49.0" minWidth="100.0" prefWidth="-1.0" text="Lines" />
<TreeTableColumn fx:id="controlNames" minWidth="100.0" prefWidth="-1.0" text="Controls" />
<TreeTableColumn fx:id="formatsNames" minWidth="100.0" prefWidth="-1.0" text="Formats" />
</columns>
</TreeTableView>
Here is the controller class
/**
* Sample Skeleton for 'AudioExplorer.fxml' Controller Class
*/
package org.cornova;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.scene.control.TreeTableColumn;
public class AudioExplorerController {
#FXML // ResourceBundle that was given to the FXMLLoader
private ResourceBundle resources;
#FXML // URL location of the FXML file that was given to the FXMLLoader
private URL location;
#FXML // fx:id="mixerName"
private TreeTableColumn<?, ?> mixerName; // Value injected by FXMLLoader
#FXML // fx:id="lineNames"
private TreeTableColumn<?, ?> lineNames; // Value injected by FXMLLoader
#FXML // fx:id="controlNames"
private TreeTableColumn<?, ?> controlNames; // Value injected by FXMLLoader
#FXML // fx:id="formatsNames"
private TreeTableColumn<?, ?> formatsNames; // Value injected by FXMLLoader
#FXML // This method is called by the FXMLLoader when initialization is complete
void initialize() {
assert mixerName != null : "fx:id=\"mixerName\" was not injected: check your FXML file 'AudioExplorer.fxml'.";
assert lineNames != null : "fx:id=\"lineNames\" was not injected: check your FXML file 'AudioExplorer.fxml'.";
assert controlNames != null : "fx:id=\"controlNames\" was not injected: check your FXML file 'AudioExplorer.fxml'.";
assert formatsNames != null : "fx:id=\"formatsNames\" was not injected: check your FXML file 'AudioExplorer.fxml'.";
}
}
Here is the main class
package org.cornova;
import java.net.URL;
import javafx.application.Application;
import javafx.beans.property.ReadOnlyStringWrapper;
import javafx.fxml.FXMLLoader;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TreeTableColumn.CellDataFeatures;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeTableColumn;
import javafx.scene.control.TreeTableView;
import javafx.stage.Stage;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Mixer;
import javax.sound.sampled.Mixer.Info;
/**
*
* #author walt
*/
public class AudioExplorer extends Application {
private URL url;
private FXMLLoader explorerLoader;
private AudioExplorerController audioController;
#Override
public void start(Stage stage) throws Exception {
stage.setTitle("Audio Explorer");
final Scene scene = new Scene(new Group(), 200, 400);
Group sceneRoot = (Group)scene.getRoot();
try {
url = getClass().getResource("/AudioExplorer.fxml");
explorerLoader = new FXMLLoader(url);
explorerLoader.setLocation(url);
audioController = explorerLoader.getController();
} catch (Exception e) {
System.out.println(e);
}
//Creating the root element
TreeItem rootNode = new TreeItem();
rootNode.setExpanded(true);
Info mixers[] = AudioSystem.getMixerInfo();
rootNode = new TreeItem<>(mixers[0]);
//Creating tree items
for (int i = 0; i < mixers.length; i++) {
rootNode.getChildren().add(new TreeItem<>(mixers[i]));
}
//Creating a column
TreeTableColumn<Info,String> mixerInfo = new TreeTableColumn<>("Mixers");
mixerInfo.setMaxWidth(1500);
//Defining cell content
mixerInfo.setCellValueFactory((CellDataFeatures<Info, String> p) ->
new ReadOnlyStringWrapper(p.getValue().getValue().getName()));
//Creating a tree table view
final TreeTableView<Info> treeTableView = new TreeTableView<>(rootNode);
treeTableView.getColumns().add(mixerInfo);
treeTableView.setMaxWidth(1500);
treeTableView.setShowRoot(false);
treeTableView.autosize();
sceneRoot.getChildren().add(treeTableView);
stage.setScene(scene);
stage.show();
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
}
This is all done under netbeans 8.2. I've done, perhaps a couple dozen of these scene builder based graphic apps perhaps 18 months ago. One thing I discovered back then was to insure the location of the css and controller source were adjusted for the name space they'd be in, which is reflected in the fxml.
The css file is empty as I only defined it in SceneBuilder at this point, which is why I did not include it (only comments).
One think I do recall from when I was starting with SceneBuilder is it's proclivity to fail silently.
Tnanks!

Answer 1

You actually need to load the fxml for the controller to be created based on the fxml. Also passing the location twice is not necessary:
url = getClass().getResource("/AudioExplorer.fxml");
explorerLoader = new FXMLLoader(url);
try {
TreeTableView<?> audioExplorer = explorerLoader.load();
audioController = explorerLoader.getController();
...
} catch ...
Furthermore there is little reason to keep a reference to the FXMLLoader instance in a field. Once you're done loading simply extract the information you need and "drop" the loader reference. Calling load a second time should be avoided anyways...

Answer 2

In addition to fabian's answer, please note that I've written some utility methods, which can reduce FXML-loading to a single statement, such as:
TreeTableView<?> audioExplorer = FXMLLoaders.load(AudioExplorer.class);
Please note, this is only possible though, if you stick to the following naming convention:
If a class "mypackage.<name>" loads a FXML file, then the FXML file
should be in the same package and be named "<name>.fxml".
The library is Open Source. Maybe you find it useful:
<dependency>
<groupId>org.drombler.commons</groupId>
<artifactId>drombler-commons-fx-core</artifactId>
<version>0.10</version>
</dependency>
You can read more about it here:
http://puces-blog.blogspot.ch/2015/03/drombler-commons-conventions-to.html