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);
}
}

How can I solve this visual glitch in my JavaFX TableView?

Left column: Checkboxes to select or deselect rows, selected by default. Right column: a String representing the amount of selected rows up to and including the row. So deselecting a checkbox in a row changes the values in the rows underneath.
The bug: Scroll down to the bottom of the table. Deselect the checkbox in the row with invite code 74. Select it again. The last three invite codes should read 73, 74 and 75 again. But quite often, they show 73, 73, 74 or 73, 74, 74.
The bug does not always occur! If it does not occur, scrolling up and down a bit with the scrollbar of the table and repeating the procedure above can make it occur.
It seems that the bug is only visual - I made it dump the contents of the ObservableList to the console and it shows the correct values. Other than this visual glitch, my app works correctly. Clicking any other control in the window (e.g. the scrollbar of the table) flips the invite codes in the table to the correct value. Switching to another workspace on my desktop and going back makes it show the right values as well.
Small image, showing the console dump of the ObservableList on the left, the bugged table on the right.
The Question, quite logically:
How can I squash this bug!?
EDIT: threw out more code as advised by Kleopatra. Thanks!
MCV:
FXMLDocumentController.java
package invcodebug;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.CheckBoxTableCell;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.util.Callback;
public class FXMLDocumentController implements Initializable {
#FXML private TableView<Person> personTable;
#FXML private TableColumn<Person, Boolean> invitedCol;
#FXML private TableColumn<Person, String> inviteCodeCol;
private final ObservableList<Person> persons
= FXCollections.observableArrayList();
#Override
public void initialize(URL location, ResourceBundle resources) {
initPersonTable();
populatePersons();
}
private void initPersonTable() {
invitedCol.setCellValueFactory(new PropertyValueFactory<>("invited"));
inviteCodeCol.setCellValueFactory(new PropertyValueFactory<>("inviteCode"));
invitedCol.setCellFactory(CheckBoxTableCell.forTableColumn(new Callback<Integer, ObservableValue<Boolean>>() {
#Override
public ObservableValue<Boolean> call(Integer param) {
doInvCode();
// SHOWS: underlying ObservableList has correct values
System.out.println("--------------------------");
for (Person p : persons) {
System.out.println(p.isInvited() + " " + p.getInviteCode()
);
}
return persons.get(param).invitedProperty();
}
}));
personTable.setItems(persons);
}
private void doInvCode() {
int invCounter = 1;
for (Person p : persons) {
if (p.isInvited()) {
p.setInviteCode(((Integer) invCounter).toString());
invCounter++;
} else p.setInviteCode("");
}
}
private void populatePersons() {
for (int i = 0; i < 75; i++) {
persons.add(new Person(true, ""));
}
}
}
Person.java
package invcodebug;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.property.SimpleStringProperty;
public class Person {
private final SimpleBooleanProperty invited;
private final SimpleStringProperty inviteCode;
public Person(boolean invited, String inviteCode) {
this.invited = new SimpleBooleanProperty(invited);
this.inviteCode = new SimpleStringProperty(inviteCode);
}
public boolean isInvited() {
return invited.get();
}
public SimpleBooleanProperty invitedProperty() {
return invited;
}
public String getInviteCode(){
return inviteCode.get();
}
public void setInviteCode(String invCode) {
this.inviteCode.set(invCode);
}
public SimpleStringProperty inviteCodeProperty() {
return inviteCode;
}
}
FXMLDocument.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TableColumn?>
<?import javafx.scene.control.TableView?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane id="AnchorPane" prefHeight="464.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1" fx:controller="invcodebug.FXMLDocumentController">
<children>
<TableView fx:id="personTable" editable="true" layoutX="26.0" layoutY="28.0" prefHeight="347.0" prefWidth="572.0" AnchorPane.leftAnchor="14.0" AnchorPane.rightAnchor="14.0" AnchorPane.topAnchor="20.0">
<columns>
<TableColumn fx:id="invitedCol" prefWidth="27.0" sortable="false" />
<TableColumn fx:id="inviteCodeCol" editable="false" prefWidth="110.0" resizable="false" sortable="false" text="Invite Code" />
</columns>
</TableView>
</children>
</AnchorPane>
InvCodeBug.java
package invcodebug;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class InvCodeBug extends Application {
#Override
public void start(Stage stage) throws Exception {
Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));
Scene scene = new Scene(root);
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}

Probably not the most technical answer, but by using personTable.requestFocus(); at the end of the doInvCode() method, the table is refreshed visually and seems to fix the problem.

JavaFX - DatePicker always returns null

DatePicker is not updating after change date.
I was looking for an answer and i found this topic:
JavaFX datepicker not updating value
, but it doesn't work.
My listener for DatePicker:
public void datePickerListener() {
this.datePicker = new DatePicker();
this.datePicker.setShowWeekNumbers(false);
this.datePicker.setOnAction(event -> {
LocalDate date = this.datePicker.getValue();
System.out.println("Selected date: " + date);
});
}
Additionally I tried get data without listener like:
public void searchAvailableAppointments() {
LocalDate date;
String date2;
date = this.datePicker.getValue();
date2 = this.datePicker.getEditor().getText();
System.out.println(date);
System.out.println(date2);
}
Maybe anyone had similar problem and found workaround?
EDIT1:
I have created simple project to check behaviour of DatePicker:
Controller class:
package sample;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.DatePicker;
import java.net.URL;
import java.time.LocalDate;
import java.util.ResourceBundle;
public class Controller implements Initializable {
#FXML
DatePicker datePicker;
#Override
public void initialize(URL location, ResourceBundle resources) {
this.datePicker = new DatePicker();
}
public void pressButton() {
LocalDate date;
date = datePicker.getValue();
System.out.println(date);
}
}
FXML file:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.DatePicker?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="142.0" prefWidth="504.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
<children>
<DatePicker fx:id="datePicker" layoutX="65.0" layoutY="58.0" prefHeight="25.0" prefWidth="295.0" />
<Button layoutX="387.0" layoutY="59.0" mnemonicParsing="false" onAction="#pressButton" prefHeight="25.0" prefWidth="80.0" text="Print result" />
</children>
</AnchorPane>
Main class:
package sample;
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{
Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
primaryStage.setTitle("Hello World");
primaryStage.setScene(new Scene(root));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
But I have still no idea how to make it work.

You should not re-initialize the DatePicker inside the initialize(). When FXMLLoader loads the fxml, it instantiates all the fields and injects them into the references which are annotated with #FXML.
If you re-initialize the field, the reference to the original object which is rendered on the view is lost and you are using the reference to the newly created object, therefore the value fetched from this object will always be null.
#Override
public void initialize(URL location, ResourceBundle resources) {
// this.datePicker = new DatePicker(); <-- Should not exist
}

JavaFX: Redirect console output to TextArea that is created in SceneBuilder

EDIT 4
I've created a simple example that should give you an idea about what's happening right now.
What's happening right now is that whenever I click the button to print "HELLO WORLD" to the TextArea, the program will hang and use 100% of the CPU. There's also no output in the Eclipse console panel too.
Main.java
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
Parent root = FXMLLoader.load(getClass().getResource("/application/test.fxml"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
MainController.java
public class MainController {
#FXML
private TextArea console;
private PrintStream ps = new PrintStream(new Console(console));
public void button(ActionEvent event) {
System.setOut(ps);
System.setErr(ps);
System.out.println("Hello World");
}
public class Console extends OutputStream {
private TextArea console;
public Console(TextArea console) {
this.console = console;
}
public void appendText(String valueOf) {
Platform.runLater(() -> console.appendText(valueOf));
}
public void write(int b) throws IOException {
appendText(String.valueOf((char)b));
}
}
}
EDIT 2: It seems that my question is way too long and hard to understand. I'm in the middle of restructuring this one.
EDIT 3
I guess I should just show everything here. What I'm trying to do is a simple GUI front-end for a CLI application. I'm a CS student and Java is our main language, so this is mainly for practice.
I've been looking every where for hours and hours but there's still no solution to this. I've tried doing the same like I did previously with Swing. The method worked fine with Swing but not with JavaFX.
Here's my (current) logger.java Class:
package application;
import java.io.*;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.application.Platform;
import javafx.fxml.Initializable;
import javafx.scene.control.*;
public class ytdlLogger extends OutputStream implements Initializable
{
private TextArea loggerPane;
public ytdlLogger(TextArea loggerPane) {
this.loggerPane = loggerPane;
}
public void appendText(String valueOf) {
Platform.runLater(() -> loggerPane.appendText(valueOf));
}
#Override
public void initialize(URL location, ResourceBundle resources) {
OutputStream out = new OutputStream() {
#Override
public void write(int b) throws IOException {
appendText(String.valueOf((char)b));
}
};
System.setOut(new PrintStream(out, true));
System.setErr(new PrintStream(out, true));
}
#Override
public void write(int b) throws IOException {
// TODO Auto-generated method stub
}
}
I don't think there's any actual problems with this. I also did add the PrintStream object to redirect System.setOut and System.setErr in the MainController class to the TextArea, but it didn't work either.
I also have another Main class, which is the main thing that loads the FXML. I tried redirecting the output from there, it almost worked. Just almost, because i stopped seeing the console outputs inside Eclipse and I knew that was a great progress.
So, what seems to be the problem here? Is it because of the FXML? I'm absolute beginner in Java and also JavaFX, this is my first JavaFX application. Any guidance is very much appreciated. Thank you in advance.
EDIT 1
Here's the Main class:
package application;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Parent;
import javafx.scene.Scene;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
Parent root = FXMLLoader.load(getClass().getResource("/application/Main.fxml"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}

You are initializing ps with the value of console before it has been initialized by the FXMLLoader. I.e you have
#FXML
private TextArea console;
private PrintStream ps = new PrintStream(new Console(console));
Clearly console is still null when you pass it to new Console(...).
You need to initialize ps after the FXMLLoader has initialized the injected fields, which you can do using the initialize method.
SSCCE:
MainController.java:
package application;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.TextArea;
public class MainController {
#FXML
private TextArea console;
private PrintStream ps ;
public void initialize() {
ps = new PrintStream(new Console(console)) ;
}
public void button(ActionEvent event) {
System.setOut(ps);
System.setErr(ps);
System.out.println("Hello World");
}
public class Console extends OutputStream {
private TextArea console;
public Console(TextArea console) {
this.console = console;
}
public void appendText(String valueOf) {
Platform.runLater(() -> console.appendText(valueOf));
}
public void write(int b) throws IOException {
appendText(String.valueOf((char)b));
}
}
}
Main.java:
package application;
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) {
try {
Parent root = FXMLLoader.load(getClass().getResource("test.fxml"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
test.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.BorderPane?>
<?import javafx.scene.control.TextArea?>
<?import javafx.scene.control.Button?>
<?import javafx.geometry.Insets?>
<BorderPane xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.MainController">
<center>
<TextArea fx:id="console"/>
</center>
<bottom>
<Button onAction="#button" text="Output">
<BorderPane.alignment>CENTER</BorderPane.alignment>
<BorderPane.margin><Insets top="5" left="5" right="5" bottom="5"/></BorderPane.margin>
</Button>
</bottom>
</BorderPane>

You do not use your controller with an FXMLLoader. Otherwise you'd get an exception, since the class has no default constructor.
If you want to use the FXMLLoader to create your ytdlLogger, add the attribute fx:controller="application.ytdlLogger" (where fx is the fxml namespace prefix) to the root element of your fxml file.
If you want to do this, you also need to change some things:
ytdlLogger needs a default constructor (i.e. either remove your constructor or create a new one without arguments).
Add the #FXML annotation to your loggerPane field to allow the FXMLLoader to access that field to assign the TextArea with the fx:id="loggerPane" attribute to it.
better remove the base class OutputStream from the controller, since you don't use it.
Add some code that prints to System.out or System.err. Otherwise it's not surprising nothing is written to your TextArea. Make sure you do this after the controller is initialized.
Your controller should look like this after the changes:
public class ytdlLogger implements Initializable
{
#FXML
private TextArea loggerPane;
public void appendText(String valueOf) {
Platform.runLater(() -> loggerPane.appendText(valueOf));
}
#Override
public void initialize(URL location, ResourceBundle resources) {
OutputStream out = new OutputStream() {
#Override
public void write(int b) throws IOException {
appendText(String.valueOf((char)b));
}
};
System.setOut(new PrintStream(out, true));
System.setErr(new PrintStream(out, true));
}
}
And the fxml should look similar to this
<?xml version="1.0" encoding="UTF-8"?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<AnchorPane xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8"
fx:controller="application.ytdlLogger"> <!-- controller goes here -->
<children>
<TextArea fx:id="loggerPane" /> <!-- the TextArea you want to use for logging -->
</children>
</AnchorPane>

onScroll listener does not working in TableView in JavaFX 2

I'm trying to use the onScroll event listener of a TableView component:
FXML:
<TableView fx:id="table" onScroll="#doSomething" tableMenuButtonVisible="true" VBox.vgrow="ALWAYS">
<columnResizePolicy>
<TableView fx:constant="CONSTRAINED_RESIZE_POLICY" />
</columnResizePolicy>
</TableView>
Java Controller:
#FXML
void doSomething(ActionEvent event)
{
System.out.println("Object: " + event.getSource());
}
But it does not working! What I'm doing wrong?
I need to capture the vertical scroller to manually control the scroll position and fetch related data according to scroll down or up.
Thanks everybody!

I think what might be happening is that the TableView includes itself is consuming the scroll event and processing it internally, so it never gets to your application handler.
Initially, I thought you might want to use onScrollTo rather than onScroll, but that doesn't seem to really address the issue.
I think the solution which works is to apply a filter on the scroll event.
In addition, you can write code that makes use of with scrollTo calls to "manually control the scroll position".
Here is some sample code you can try (Java 8):
TableScrollerApp.java
package finder;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Group;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class TableScrollerApp extends Application {
#Override public void start(final Stage stage) throws Exception {
FXMLLoader loader = new FXMLLoader(
getClass().getResource("tablescroller.fxml")
);
Parent parent = loader.load();
stage.setScene(new Scene(new Group(parent)));
stage.show();
}
public static void main(String[] args) {
Application.launch(args);
}
}
TableScrollerController.java
package finder;
import javafx.beans.property.ReadOnlyStringProperty;
import javafx.beans.property.ReadOnlyStringWrapper;
import javafx.fxml.FXML;
import javafx.scene.control.ScrollToEvent;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.input.ScrollEvent;
import java.util.Arrays;
import java.util.stream.Collectors;
public class TableScrollerController {
private static final String[] fruitNames = {
"apples", "oranges", "pears", "peaches",
"guavas", "bananas", "jackfruit", "durians"
};
#FXML
private TableView<Fruit> fruitsTable;
#FXML
private TableColumn<Fruit, String> fruitsColumn;
#FXML
protected void initialize() {
fruitsColumn.setCellValueFactory(new PropertyValueFactory<>("name"));
fruitsTable.addEventFilter(ScrollEvent.ANY, event ->
System.out.println("Coded scroll filter: " + event)
);
fruitsTable.getItems().setAll(
Arrays.stream(fruitNames)
.map(Fruit::new)
.collect(Collectors.toList())
);
fruitsTable.scrollTo(5);
}
#FXML
protected void onScrollHandler(ScrollEvent scrollEvent) {
System.out.println("FXML referenced scroll handler: " + scrollEvent);
}
#FXML
protected void onScrollToHandler(ScrollToEvent<Integer> scrollToEvent) {
System.out.println("FXML referenced onScroll handler: " + scrollToEvent);
}
public static class Fruit {
private ReadOnlyStringWrapper name;
public Fruit(String name) {
this.name = new ReadOnlyStringWrapper(name);
}
public String getName() {
return name.get();
}
public ReadOnlyStringProperty nameProperty() {
return name;
}
}
}
tablescroller.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<TableView fx:id="fruitsTable"
maxHeight="-Infinity" maxWidth="-Infinity"
minHeight="-Infinity" minWidth="-Infinity"
onScroll="#onScrollHandler"
onScrollTo="#onScrollToHandler"
prefHeight="100.0" prefWidth="250.0"
xmlns="http://javafx.com/javafx/8"
xmlns:fx="http://javafx.com/fxml/1"
fx:controller="finder.TableScrollerController">
<columns>
<TableColumn fx:id="fruitsColumn"
maxWidth="800.0" minWidth="200.0" prefWidth="-1.0"
text="Fruits" />
</columns>
</TableView>