Develop Reference

Issues with setting bounds of NumberAxis based on user input in FXML JavaFX application

SUMMARY: I am trying to design an application where the user inputs into TextFields, and upon clicking a button ONCE:
The values are retrieved
The scene switches to one containing a lineChart
The number axes' bounds are set corresponding to the values entered before.
However I'm finding it very hard to understand how to make the program flow correctly for this to work. My main issues are with switching the scene then accessing x_axis and y_axis, where for some reason "this.x_axis" is null.
Main Class:
public class Main extends Application {
#Override
public void start(Stage stage) throws IOException {
Parent root = FXMLLoader.load(getClass().getResource("menuScene.fxml"));
Scene scene = new Scene(root);
stage.setTitle("FT_Tool");
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch();
}
}
Controller: (calculate is called after clicking button)
public class MenuController {
private Stage stage;
private Scene scene;
private Parent root;
#FXML
private TextField funcBox;
#FXML
private TextField sampBox;
#FXML
private TextField limitBox;
Expression func;
double sampFreq;
double limit;
#FXML
public void calculate(ActionEvent event) throws IOException{
func = new ExpressionBuilder(funcBox.getText()).variables("x").build();
sampFreq = Double.parseDouble(sampBox.getText());
limit = Double.parseDouble(limitBox.getText());
//=== SWITCHING SCENES ===//
root = FXMLLoader.load(getClass().getResource("graphScene.fxml"));
stage = (Stage) ((Node) event.getSource()).getScene().getWindow();
scene = new Scene(root);
stage.setScene(scene);
stage.show();
graphing();
}
#FXML
private LineChart sampleGraph;
#FXML
private NumberAxis x_axis;
#FXML
private NumberAxis y_axis;
public void graphing(){
x_axis.setUpperBound(limit);
}
}
2nd Scene:
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/16" xmlns:fx="http://javafx.com/fxml/1">
<children>
<LineChart fx:id="sampleGraph" layoutX="24.0" layoutY="16.0" prefHeight="368.0" prefWidth="552.0" title="Samples taken">
<xAxis>
<NumberAxis fx:id="x_axis" autoRanging="false" label="Time (s)" tickUnit="1.0"/>
</xAxis>
<yAxis>
<NumberAxis fx:id="y_axis" autoRanging="false" label="Amplitude (m)"/>
</yAxis>
</LineChart>
</children>
</AnchorPane>
When I run it, application runs fine and after clicking button the scene switches and linechart is shown but without the right bounds.
This line of code: x_axis.setUpperBound(limit) causes the following error:
Caused by: java.lang.NullPointerException: Cannot invoke "javafx.scene.chart.NumberAxis.setUpperBound(double)" because "this.x_axis" is null

Despite not having the fx:controller attribute defined in your FXML file, it looks like—based on your FXML controller class—you're trying to use the same FXML controller class with multiple FXML files. This is strongly discouraged. By default, a new controller instance is created every time the FXML file is loaded. Consequently, it quickly becomes difficult to reason about which fields should have been injected (i.e., non-null) at any given time. An FXML file should have a one-to-one mapping with an FXML controller class (or possibly no controller).
You have two views, which suggests two FXML files and thus two FXML controller classes. When you load the second view, you should communicate to its controller the needed information. For trivial applications you can do this directly, but for more complex applications it would be better to communicate via a model shared between the two controllers.
Example
Here's an example (based on your code but simplified for demonstration). It only asks for the upper bounds of the X and Y axes and then graphs random data within those bounds. It also makes use of TextFormatter to make it easier to grab the values out of the TextFields, and to ensure the user only enters positive integers.
FXML files are assumed to be located in the com.example package.
Main.java:
package com.example;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class Main extends Application {
#Override
public void start(Stage primaryStage) throws Exception {
var root = FXMLLoader.<Parent>load(Main.class.getResource("Form.fxml"));
primaryStage.setScene(new Scene(root, 1000, 650));
primaryStage.show();
}
}
Form.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.GridPane?>
<GridPane xmlns="http://javafx.com/javafx" xmlns:fx="http://javafx.com/fxml"
fx:controller="com.example.FormController" alignment="CENTER" vgap="20" hgap="15">
<Label text="Upper X Bound:" GridPane.rowIndex="0" GridPane.columnIndex="0"/>
<TextField fx:id="xField" GridPane.rowIndex="0" GridPane.columnIndex="1" GridPane.columnSpan="2"/>
<Label text="Upper Y Bound:" GridPane.rowIndex="1" GridPane.columnIndex="0"/>
<TextField fx:id="yField" GridPane.rowIndex="1" GridPane.columnIndex="1" GridPane.columnSpan="2"/>
<Button text="Graph" onAction="#handleOnGraph" defaultButton="true" GridPane.rowIndex="2"
GridPane.columnIndex="2" GridPane.halignment="RIGHT"/>
</GridPane>
FormController.java:
package com.example;
import java.io.IOException;
import java.util.function.UnaryOperator;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.control.TextField;
import javafx.scene.control.TextFormatter;
import javafx.util.converter.IntegerStringConverter;
public class FormController {
#FXML private TextField xField;
#FXML private TextField yField;
private TextFormatter<Integer> xFieldFormatter;
private TextFormatter<Integer> yFieldFormatter;
#FXML
private void initialize() {
UnaryOperator<TextFormatter.Change> filter =
change -> {
if (change.getControlNewText().matches("\\d*")) {
return change;
}
return null;
};
xFieldFormatter = new TextFormatter<>(new IntegerStringConverter(), 50, filter);
xField.setTextFormatter(xFieldFormatter);
yFieldFormatter = new TextFormatter<>(new IntegerStringConverter(), 50, filter);
yField.setTextFormatter(yFieldFormatter);
}
#FXML
private void handleOnGraph(ActionEvent event) throws IOException {
event.consume();
int upperX = xFieldFormatter.getValue();
int upperY = yFieldFormatter.getValue();
var loader = new FXMLLoader(FormController.class.getResource("Chart.fxml"));
xField.getScene().setRoot(loader.load());
loader.<ChartController>getController().graph(upperX, upperY);
}
}
Chart.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.chart.LineChart?>
<?import javafx.scene.chart.NumberAxis?>
<LineChart fx:id="chart" xmlns="http://javafx.com/javafx" xmlns:fx="http://javafx.com/fxml"
fx:controller="com.example.ChartController">
<xAxis>
<NumberAxis fx:id="xAxis" upperBound="50" autoRanging="false"/>
</xAxis>
<yAxis>
<NumberAxis fx:id="yAxis" upperBound="50" autoRanging="false"/>
</yAxis>
</LineChart>
ChartController.java:
package com.example;
import javafx.collections.FXCollections;
import javafx.fxml.FXML;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
public class ChartController {
#FXML private LineChart<Number, Number> chart;
#FXML private NumberAxis xAxis;
#FXML private NumberAxis yAxis;
void graph(int upperX, int upperY) {
xAxis.setUpperBound(upperX);
yAxis.setUpperBound(upperY);
generateAndGraphRandomData();
}
private void generateAndGraphRandomData() {
var data = FXCollections.<XYChart.Data<Number, Number>>observableArrayList();
for (int x = 0; x <= xAxis.getUpperBound(); x++) {
int y = (int) (Math.random() * yAxis.getUpperBound());
data.add(new XYChart.Data<>(x, y));
}
var series = new XYChart.Series<>("Random Demo Data", data);
chart.getData().add(series);
}
}

Interact between several FXMLs

I'm trying to write my first application with javaFX and FXML files, but I got stuck with accesing variables of the FXMLs.
I am able to start the program with the first scene (first FXML). There is a button I'm able to interact with, and the first scene hides and the second scene appears. In that scene, the user has to insert a value in a text field. I'm able to save this into a variable by confirming this input over another button.
This button click hides the second scene and opens the first scene again. Now I want to set the value of a label in that first scene to the value of the variable I saved the user's input in. But this throws an error message.
It seems like this label value is not accessable, even if this label is part of the currently loaded FXML, but I am able to get the value of a label of the second FXML (user interaction field), which isn't visible anymore.
Can anyone help me, how to make this Label of the first FXML readable and changable?
My code is quite long, but I tired to give you the most important parts:
#FXML
private Label RollsMax;
#FXML
private TextField roll_input;
#FXML
private String amountRolls;
... // several more declarations
#FXML
void btn_confirmInput_onClick(ActionEvent event){ //btn_confirmInput is part of scene2.fxml
event.consume();
amountRolls=roll_input.getText();
System.out.println(amountRolls); // here I get the result of the user's input
try{
root=FXMLLoader.load(getClass().getResource("project/scene1.fxml"));
stage=(Stage)((Node)event.getSource()).getScene().getWindow();
scene=new Scene(root);
stage.setScene(scene);
stage.show();
} //end try
catch (IOException e){
e.printStackTrace();
} //end catch
RollsMax.setText(amountRolls); // THIS LINE IS NOT WORKING AS RollsMax SEEMS NOT AVAILABLE, EVEN IF IT IS PART OF SCENE1.fxml
} // end btn_confirmInput_onClick()
Any ideas? The error I get is 'java.lang.RuntimeException: java.lang.reflect.InvocationtargetException' as well as a'java.lang.NullPointerException'.
Thanks a lot!
Endcoder

To share data between the scenes, we'll introduce a Model class that holds the shared information:
public class Model {
private SimpleStringProperty valueProperty = new SimpleStringProperty("N/A");
public SimpleStringProperty getValueProperty() {
return valueProperty;
}
}
And an interface to be implemented by the controllers of the two scenes (actually the controllers of the two roots of the two scenes).
The interface adds the functionality of injection a Model into the controller:
public interface Controller {
void setModel(Model model);
}
sceneOne.fxml with a button to switch scene and a label to display user's input:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity"
prefHeight="300.0" prefWidth="400.0" xmlns="http://javafx.com/javafx/16"
xmlns:fx="http://javafx.com/fxml/1" fx:controller="SceneOneController">
<children>
<Label layoutX="159.0" layoutY="40.0" text="Scene 1">
<font>
<Font size="24.0" />
</font>
</Label>
<Button layoutX="264.0" layoutY="246.0" mnemonicParsing="false" onAction="#changeScene" prefHeight="26.0" prefWidth="102.0" text="Get Input" />
<Label fx:id="inputValue" layoutX="187.0" layoutY="142.0" text="Label" />
</children>
</AnchorPane>
And its controller which implements the Controller interface:
public class SceneOneController implements Controller {
#FXML Label inputValue;
private Model model;
public void changeScene(ActionEvent e) {
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("sceneTwo.fxml"));
Parent root = loader.load();
Controller controller = loader.getController(); //get a reference to sceneTwo controller
controller.setModel(model);
Stage stage = (Stage)((Node)e.getSource()).getScene().getWindow();
stage.setScene(new Scene(root));
} catch (Exception ex) {
ex.printStackTrace();
}
}
#Override
public void setModel(Model model) {
this.model = model;
if(model != null){
inputValue.textProperty().unbind();
inputValue.textProperty().bind(model.valueProperty);
}
}
}
sceneTwo.fxml with a button to switch scene and a TextField for the user's input:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>
<AnchorPane fx:id="main" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="300.0" prefWidth="400.0" xmlns="http://javafx.com/javafx/16" xmlns:fx="http://javafx.com/fxml/1" fx:controller="SceneTwoController">
<children>
<Label layoutX="150.0" layoutY="41.0" text="Scene 2">
<font>
<Font size="24.0" />
</font>
</Label>
<Button layoutX="264.0" layoutY="246.0" mnemonicParsing="false" onAction="#changeScene" prefHeight="26.0" prefWidth="102.0" text="Update" />
<TextField fx:id="inputValue" layoutX="121.0" layoutY="138.0" prefHeight="25.0" prefWidth="162.0" />
</children>
</AnchorPane>
And its controller:
public class SceneTwoController implements Controller {
#FXML TextField inputValue;
private Model model;
public void changeScene(ActionEvent e) {
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("sceneOne.fxml"));
Parent root = loader.load();
Controller controller = loader.getController(); //get a reference to sceneOne controller
controller.setModel(model);
Stage stage = (Stage)((Node)e.getSource()).getScene().getWindow();
stage.setScene(new Scene(root));
} catch (Exception ex) {
ex.printStackTrace();
}
}
#Override
public void setModel(Model model) {
this.model = model;
if(model != null){
inputValue.textProperty().unbind();
model.valueProperty.bind(inputValue.textProperty());
}
}
}
And finally the application to test it all:
public class SwitchSceneMVC extends Application {
#Override
public void start(Stage primaryStage) throws Exception{
FXMLLoader loader = new FXMLLoader(getClass().getResource("sceneOne.fxml"));
Parent root = loader.load();
Model model = new Model();
Controller controller = loader.getController();
controller.setModel(model);
primaryStage.setScene(new Scene(root));
primaryStage.show();
}
public static void main(String[] args) {
launch(null);
}
}

Use a controller class for every FXML. Then you should be able to interact between them with public methods.
Especially when just hidinng the first scene you should then be able to just write from one scene to the other one.
Alternatively: while starting the second scene make a parameter where you bring the instance of the first scene. Than you should be able to use the needed methods on the first scenes instance.
Like
Code Scene one
#FXML
private void startSceneTwoButton(){
new SceneTwo(this);
}
Code Scene two
FirstScene scene;
public SecondScene(FirstScene scene){
this.scene = scene;
//some code
}
#FXML
private void button(){
scene.enterValue(value);
}

Cannot invoke "javafx.scene.control.ComboBox.getItems()" because the return value of "Controller.getMyBox()" is null

Somehow, I cannot add items to my ComboBox variable from another class as it always says either the value of variable is null or the return value of its getter is null.
I use Scene Builder to build Sample.fxml, with controller as Controller class, luanch the whole thing form UserInterface class
FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.ComboBox?>
<?import javafx.scene.layout.BorderPane?>
<BorderPane xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Controller">
<center>
<ComboBox fx:id="myBox" prefWidth="150.0" BorderPane.alignment="CENTER" />
</center>
</BorderPane>
Controller
public class Controller {
#FXML
private ComboBox<String> myBox;
public ComboBox<String> getMyBox() {
return myBox;
}
public void initialize() {
ObservableList<String> defaultTicker = FXCollections.observableArrayList("Something");
myBox.getItems().addAll(defaultTicker);
}
}
UserInterface
public class UserInterface extends Application {
#Override
public void start(Stage primaryStage) {
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("Sample.fxml"));
Parent root = loader.load();
Controller controller = new Controller();
primaryStage.setTitle("Title");
primaryStage.setScene(new Scene(root));
primaryStage.show();
List<String> addStuff = new ArrayList<String>();
addStuff.add("a");
addStuff.add("b");
addStuff.add("c");
controller.getMyBox().getItems().addAll(addStuff);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
After running, the interface appears, with only the option "Something" in it. So I guess it initialize fine?
The interface after launch
What did I do wrong? I couldn't seem to find any solutions so far.
Thanks in advance.

How do I update the center node of a BorderPane using FXML Controller

I am trying to update the center node of a BorderPane using FXML. I have created a VBox on the left with Buttons and when clicked they are supposed to update the center node however the center node does not update. Can someone shed some light on what I am doing incorrectly?
I know the buttons events work (they print to the screen usiong println) but it will not update the UI.
The root nodes .fxml (the BorderPane):
<?import javafx.scene.layout.BorderPane?>
<BorderPane xmlns:fx="http://javafx.com/fxml" fx:id="rootPane">
<left>
</left>
<center>
</center>
</BorderPane>
The menu
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.control.Button?>
<VBox fx:controller="" xmlns:fx="http://javafx.com/fxml" >
<children>
<Button text="Dashboard" fx:id="dashboardButton" onAction="#dashboardButtonEvent" />
<Button text="Sales" fx:id="salesButton" onAction="#salesButtonEvent" />
</children>
</VBox>
The MenuController
public class MenuController implements Initializable {
#FXML
private BorderPane rootPane;
#FXML
private Button dashboardButton; //same name as in the menu.fxml file
#FXML
private Button salesButton; //same name as in the menu.fxml file
#FXML
private void dashboardButtonEvent(ActionEvent event) {
try {
VBox dashboard = FXMLLoader.load(getClass().getResource("../../../fxml/dashboard.fxml"));
rootPane = FXMLLoader.load(getClass().getResource("../../../fxml/root.fxml"));
rootPane.setCenter(dashboard);
} catch (IOException e) { System.out.println(e); }
}
#FXML
private void salesButtonEvent(ActionEvent event) {
try {
VBox sales = FXMLLoader.load(getClass().getResource("../../../fxml/sales.fxml"));
rootPane = FXMLLoader.load(getClass().getResource("../../../fxml/root.fxml"));
rootPane.setCenter(sales);
} catch (IOException e) { System.out.println(e); }
}
#Override
public void initialize(URL url, ResourceBundle resourceBundle) {
}
}
I assume where I am going wrong is the way I am going about assigning the root pane using rootPane = FXMLLoader.load(getClass().getResource("../../../fxml/root.fxml"));. If thats the case, how do I get the current rootPane from the existing scene?

javafx mediaview only the audio is playing

Im trying to embed a video in a website to a mediaview of a simple javafx application. Ive got a sample code which I used as my javafx code. It opens the scene and plays the audio but wont play the video. How can I make it play the audio? Im using netbeans IDE 8.0.2,JavaFx 8 and scene builder 2.0
The Code ive tried is below.
Thanx in advanced.
#FXML MediaView mdv;
Media media;
public static MediaPlayer mpl;
#Override
public void initialize(URL url, ResourceBundle rb) {
media=new Media("http://download.oracle.com/otndocs/products/javafx/oow2010-2.flv");
mpl=new MediaPlayer(media);
mpl.setAutoPlay(true);
mdv=new MediaView(mpl);
mpl.play();
mpl.setOnError(new Runnable() {
#Override public void run() {
System.out.println("Current Error: " + mpl.getError());
}
});
}
This is how I load the children to the stage
public class Production extends Application {
#Override
public void start(Stage stage) throws Exception {
Parent root = FXMLLoader.load(getClass().getResource("Vdo.fxml"));
Scene scene = new Scene(root);
stage.setScene(scene);
stage.show();
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
the FXML Ive got after creating the GUI from scene builder is below
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.media.*?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<AnchorPane id="AnchorPane" prefHeight="400.0" prefWidth="600.0"
xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1"
fx:controller="production.VdoController">
<children>
<MediaView fx:id="mdv" fitHeight="300.0" fitWidth="300.0" layoutX="125.0" layoutY="85.0" />
<Button layoutX="235.0" layoutY="51.0" mnemonicParsing="false" text="Button" />
</children>
</AnchorPane>

You are re-initializing the MediaView that has been initialized by the FXMLoader. Never do this, because you will loose the reference to the original node.
You should just set the MediaPlayer to the MediaView instead of re-initializing it by using the setMediaPlayer().
#Override
public void initialize(URL url, ResourceBundle rb) {
media=new Media("http://download.oracle.com/otndocs/products/javafx/oow2010-2.flv");
mpl=new MediaPlayer(media);
mpl.setAutoPlay(true);
mdv.setMediaPlayer(mpl);
mpl.play();
}