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);
}

JavaFX - RadioButtons in TableCell with Add Data Button

I'm currently working on an application where I use a TableView including RadioButtons in one TableCell. For that I created an own RadioButtonCell class. I also have a "Add new Row"-Button to let the user add some additional rows. After clicking the "Add" button a third time, I get more RadioButtonCells than rows. I don't find the mistake in my code.
Here a screenshot after clicking the Button a third time:
RadioButtonCell:
import java.util.EnumSet;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.geometry.Pos;
import javafx.scene.control.RadioButton;
import javafx.scene.control.TableCell;
import javafx.scene.control.Toggle;
import javafx.scene.control.ToggleGroup;
import javafx.scene.layout.HBox;
public class RadioButtonCell<S,T extends Enum<T>> extends TableCell<S,T>{
private EnumSet<T> enumeration;
public RadioButtonCell(EnumSet<T> enumeration) {
this.enumeration = enumeration;
}
#Override
protected void updateItem(T item, boolean empty)
{
super.updateItem(item, empty);
if (!empty)
{
// GUI
HBox hb = new HBox(7);
hb.setAlignment(Pos.CENTER);
final ToggleGroup group = new ToggleGroup();
// create a radio button for each 'element' of the enumeration
for (Enum<T> enumElement : enumeration) {
RadioButton radioButton = new RadioButton(enumElement.toString());
radioButton.setUserData(enumElement);
radioButton.setToggleGroup(group);
hb.getChildren().add(radioButton);
if (enumElement.equals(item)) {
radioButton.setSelected(true);
}
}
// issue events on change of the selected radio button
group.selectedToggleProperty().addListener(new ChangeListener<Toggle>() {
#SuppressWarnings("unchecked")
#Override
public void changed(ObservableValue<? extends Toggle> observable,
Toggle oldValue, Toggle newValue) {
getTableView().edit(getIndex(), getTableColumn());
RadioButtonCell.this.commitEdit((T) newValue.getUserData());
}
});
setGraphic(hb);
}
}
}
Model:
public class Points {
private final SimpleObjectProperty<Participation> participation = new SimpleObjectProperty<Participation>(); // radio buttons
public static enum Participation {
NONE, HALO, BORDER;
public String toString() {
return super.toString().toLowerCase();
};
}
/**
* Constructor.
* #param <Participation>
*/
public Points(Participation p) {
this.participation.setValue(p);
public void setParticipation(Participation p){
participation.set(p);
}
public Participation getParticipation(){
return participation.get();
}
public SimpleObjectProperty<Participation> ParticipationProperty() {
return participation;
}
}
FXML:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.SplitPane?>
<?import javafx.scene.control.Tab?>
<?import javafx.scene.control.TabPane?>
<?import javafx.scene.control.TableColumn?>
<?import javafx.scene.control.TableView?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<VBox prefHeight="900.0" prefWidth="1250.0" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1" fx:controller="address.view.DataOverviewController">
<children>
<SplitPane fx:id="splitPaneVertical" prefHeight="776.0" prefWidth="1200.0" VBox.vgrow="ALWAYS">
<items>
<TabPane fx:id="tabPane" stylesheets="#Theme.css">
<tabs>
<Tab text="Points">
<content>
<SplitPane fx:id="splitPaneHorizontal" dividerPositions="0.949874686716792" orientation="VERTICAL" stylesheets="#Theme.css">
<items>
<TableView fx:id="pointsDataTable">
<columns>
<TableColumn fx:id="pointsBackgroundColumn" prefWidth="200.0" resizable="false" text="Background" />
</columns>
</TableView>
<AnchorPane SplitPane.resizableWithParent="false">
<children>
<HBox fx:id="pointsHBoxButton" alignment="CENTER" prefHeight="35.0" prefWidth="1016.0" spacing="20.0" stylesheets="#Theme.css" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<children>
<Button fx:id="pointsAddButton" mnemonicParsing="false" onAction="#handleAddPoints" text="Add" />
</children>
</HBox>
</children>
</AnchorPane>
</items>
</SplitPane>
</content>
</Tab>
</tabs>
</TabPane>
</items>
</SplitPane>
Controller:
public class DataOverviewController {
#FXML
private TableView<Points> pointsDataTable;
#FXML
private TableColumn<Points, Participation> pointsBackgroundColumn;
#FXML
private Button pointsButtonAdd;
public DataOverviewController() {
}
#FXML
private void initialize() {
// select multipe rows, make rows editable
pointsDataTable.setEditable(true);
pointsDataTable.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
linesDataTable.setEditable(true);
pointsBackgroundColumn.setCellFactory((param) -> new RadioButtonCell<Points, Participation>(EnumSet.allOf(Participation.class)));
pointsBackgroundColumn.setCellValueFactory(new PropertyValueFactory<Points, Participation>("Participation"));
pointsBackgroundColumn.setOnEditCommit(
new EventHandler<CellEditEvent<Points, Participation>>() {
#Override
public void handle(CellEditEvent<Points, Participation> t) {
((Points) t.getTableView().getItems().get(
t.getTablePosition().getRow())
).setParticipation(t.getNewValue());
}
}
);
public void setMainConfig(MainConfig mainConfig) {
// Add observable list data to the table
pointsDataTable.setItems(mainConfig.getTableDataPoints());
}
#FXML
private void handleAddPoints() {
// create new record and add it to the tableview
Points dataPoints = new Points(0, "Points", "TabFileName.tab",Participation.NONE, false, false, 18, "new");
pointsDataTable.getItems().add(dataPoints);
}
}
}
I reduced my code to the important parts. Maybe someone can help?
Thanks.

Items can be added as well as removed from TableCells. This means you need to handle the case where the TableCell becomes empty by undoing any changes done to the cell when a item was added. Otherwise there may be TableCells that look as if they contain a item although they are actually empty.
A updateItem method should look like this:
#Override
protected void updateItem(T item, boolean empty) {
super.updateItem(item, empty);
if (empty) {
// modifications to restore the empty state
} else {
// customized way of displaying the item
}
}
Furthermore I do not recommend recreating the Nodes for displaying the item in the cell every time the item is changed, since this means you'll have a lot of unnecessary node creations which is the thing TableView is trying to avoid by reusing cells. Store them in fields and keep them for later use instead.

Getting a listener class to change values of a Label in a controller

I'm new to Java and JavaFX -- I'm making a small player application and are finding it a challenge to get the duration timer to display on a label on my display.
My latest attempt was creating a TimeListener.java class which would change the duration values for each new song played and set them on the label in another class but that idea is flawed as I came across a non-static error.
TrackPlayer object class
private MediaPlayer player;
private Media track;
private String filepath;
private Duration duration;
public TrackPlayer(String filepath) {
this.filepath = filepath;
track = new Media(filepath);
player = new MediaPlayer(track);
player.setOnReady(() -> {
duration = track.getDuration();
System.out.println("Duration: " + duration);
});
player.currentTimeProperty().addListener(new TimeListener());
}
TimeListener class
public class TimeListener implements ChangeListener<Duration> {
#Override
public void changed(ObservableValue<? extends Duration> observable, Duration oldValue, Duration newValue) {
TrackPlayerController.setTime(newValue.toString());
}
}
FXML Controller class
#FXML
private Label runTime;
...
public void setTime(String time) {
//runTime.setText(time);
}
How else could I approach this problem? I want a label which would display something like 00:00:00 (elapsed) / 00:00:00 (duration) but I'm sure if I just get the duration working I can also get the elapsed time working.
Example with the same problem but most if not all features removed
TrackPlayer class
package logic;
import javafx.beans.property.ReadOnlyObjectProperty;
import javafx.scene.media.Media;
import javafx.scene.media.MediaPlayer;
import javafx.scene.media.MediaPlayer.Status;
import javafx.util.Duration;
public class TrackPlayer {
private MediaPlayer player;
private Media track;
private String filepath;
private Duration duration;
public TrackPlayer(String filepath) {
this.filepath = filepath;
track = new Media(filepath);
player = new MediaPlayer(track);
player.setOnReady(() -> {
duration = track.getDuration();
System.out.println("Duration: " + duration);
});
}
public void playSong() {
System.out.println("Playing song");
player.play();
}
public void pauseSong() {
System.out.println("Pausing song");
player.pause();
}
public void stopSong() {
System.out.println("Stopping song");
player.stop();
}
public Status getStatus() {
return player.getStatus();
}
public Duration getDuration() {
return duration;
}
public Duration getCurrentTime() {
return player.getCurrentTime();
}
public Duration getStartTime() {
return player.getStartTime();
}
public void setSeek(Duration duration) {
player.seek(duration);
}
public Media getMedia() {
return player.getMedia();
}
public ReadOnlyObjectProperty<Duration> currentTimeProperty() {
return player.currentTimeProperty();
}
public Duration getTotalDuration() {
return player.getTotalDuration();
}
}
TrackPlayerController class
package gui;
import java.io.IOException;
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;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableRow;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import logic.TrackPlayer;
import logic.Track;
public class TrackPlayerController implements Initializable {
#FXML
private TableView<Track> playingTable;
#FXML
private TableColumn<Track, String> playingTitleCol;
#FXML
private TableColumn<Track, String> playingArtistCol;
#FXML
private TableColumn<Track, String> playingGenreCol;
#FXML
private TableColumn<Track, String> playingRunTimeCol;
#FXML
private Label runTime;
private TrackPlayer player;
#Override
public void initialize(URL fxmlFileLocation, ResourceBundle resources) {
playingTitleCol.setCellValueFactory(new PropertyValueFactory<>("TrackTitle"));
playingArtistCol.setCellValueFactory(new PropertyValueFactory<>("TrackArtist"));
playingGenreCol.setCellValueFactory(new PropertyValueFactory<>("TrackGenre"));
playingRunTimeCol.setCellValueFactory(new PropertyValueFactory<>("RunTime"));
player.currentTimeProperty().addListener(observable -> {
setTime(player.getCurrentTime()
+ " / "
+ player.getTotalDuration());
});
playingTable.setRowFactory(tv -> { // Function for double-click to play (load)
TableRow<Track> row = new TableRow<>();
row.setOnMouseClicked(event -> {
if (event.getClickCount() == 2 && (!row.isEmpty())) {
play();
}
});
return row;
});
}
#FXML
private void play() {
}
#FXML
private void reset(ActionEvent e) {
}
#FXML
private void remove(ActionEvent e) {
}
#FXML
private void removeAll(ActionEvent e) {
}
#FXML
private void search(ActionEvent e) throws IOException {
}
public void setTime(String time) {
runTime.setText(time);
}
}
TrackPlayerMain class
package gui;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.fxml.FXMLLoader;
import javafx.scene.layout.BorderPane;
public class TrackPlayerMain extends Application {
#Override
public void start(Stage primaryStage) throws Exception {
BorderPane root = new BorderPane();
FXMLLoader trackPlayerLoader = new FXMLLoader(getClass().getResource("TrackPlayer.fxml"));
root.setCenter(trackPlayerLoader.load());
TrackPlayerController trackPlayerController = trackPlayerLoader.getController();
Scene scene = new Scene(root, 600, 400);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
TrackPlayer FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.paint.*?>
<?import javafx.scene.text.*?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="gui.TrackPlayerController">
<children>
<Slider fx:id="timeSlider" layoutX="9.0" layoutY="333.0" prefHeight="25.0" prefWidth="582.0" />
<Label alignment="BOTTOM_LEFT" layoutX="23.0" layoutY="10.0" prefHeight="17.0" prefWidth="75.0" text="Now Playing" />
<Button fx:id="play" layoutX="250.0" layoutY="361.0" mnemonicParsing="false" onAction="#play" prefHeight="25.0" prefWidth="100.0" text="Play" />
<Button fx:id="ff" layoutX="356.0" layoutY="361.0" mnemonicParsing="false" text=">>" />
<Button fx:id="rw" layoutX="211.0" layoutY="361.0" mnemonicParsing="false" text="<<" />
<Button fx:id="reset" layoutX="22.0" layoutY="361.0" mnemonicParsing="false" onAction="#reset" prefWidth="59.0" text="Reset" />
<Button fx:id="remove" layoutX="498.0" layoutY="305.0" mnemonicParsing="false" onAction="#remove" prefWidth="83.0" text="Remove" />
<Label fx:id="runTime" alignment="TOP_CENTER" layoutX="516.0" layoutY="350.0" prefHeight="17.0" prefWidth="75.0" text="00:00 / 00:00" textFill="#00000065">
<font>
<Font size="11.0" />
</font>
</Label>
<Button fx:id="removeAll" layoutX="401.0" layoutY="305.0" mnemonicParsing="false" onAction="#removeAll" prefHeight="25.0" prefWidth="83.0" text="Remove All" />
<TableView fx:id="playingTable" layoutX="18.0" layoutY="32.0" prefHeight="263.0" prefWidth="563.0">
<columns>
<TableColumn fx:id="playingTitleCol" editable="false" prefWidth="140.75" resizable="false" text="Title" />
<TableColumn fx:id="playingArtistCol" editable="false" prefWidth="140.75" resizable="false" text="Artist" />
<TableColumn fx:id="playingGenreCol" editable="false" prefWidth="140.75" resizable="false" text="Genre" />
<TableColumn fx:id="playingRunTimeCol" prefWidth="140.75" resizable="false" text="Run Time" />
</columns>
<columnResizePolicy>
<TableView fx:constant="CONSTRAINED_RESIZE_POLICY" />
</columnResizePolicy>
</TableView>
<Button fx:id="search" layoutX="303.0" layoutY="305.0" mnemonicParsing="false" onAction="#search" prefHeight="0.0" prefWidth="83.0" text="Search" />
</children>
</AnchorPane>
From what I assume it is throwing NullPointerException because it's trying to initalize the listener with the current time and duration however the player object has not been created yet (as no song is played right from the start, only when selected and pressed play) -- if that is the case how can I add the listener?
Edit: Okay so I've tested what causes the NullPointerException and it's the player being null, as the program launches when I do this.
if (player != null) {
player.currentTimeProperty().addListener(observable -> {
runTime.setText(player.getCurrentTime()
+ " / "
+ player.getTotalDuration());
});
}
However when I do this the listener doesn't get initialized as the runTime label does not change at all. This is my problem that I'm trying to solve. How can I go about fixing it?

Non-FXML Based Sample
Here is some sample code, it doesn't use FXML, but the principles are the same whether you have FXML involved or not. You just add a listener to the relevant property and take action as it changes. I didn't format the duration as you have in your question, but that is trivial and different from the problem of responding to changes in the listener.
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.scene.media.*;
import javafx.stage.Stage;
public class VideoPlayerExample extends Application {
private static final String MEDIA_LOC =
"http://download.oracle.com/otndocs/products/javafx/oow2010-2.flv";
#Override
public void start(final Stage stage) throws Exception {
final MediaPlayer oracleVid = new MediaPlayer(
new Media(MEDIA_LOC)
);
Label progress = new Label();
oracleVid.currentTimeProperty().addListener(observable -> {
progress.setText(
oracleVid.getCurrentTime()
+ " / "
+ oracleVid.getTotalDuration()
);
});
VBox layout = new VBox(10, progress, new MediaView(oracleVid));
stage.setScene(new Scene(layout, 540, 208));
stage.show();
oracleVid.play();
}
public static void main(String[] args) throws Exception {
launch(args);
}
}
where should I place the listener?
It's difficult to recommend without seeing full code, so I'll just make some assumptions and provide advice on that to get you started. So, let's assume that:
You are defining and embedding your custom media player control in FXML similar to the mechanism outlined in:
How to create an FXML file for an already created new component in java than add it to scene builder?
The duration tracking label is (for some reason) not part of the custom media control.
Your encompassing FXML therefore includes two components, your custom media player and the duration label.
In this case the listener is situated in the controller for the encompassing FXML file that includes the media player and the duration label and is set up during the initialize() call for that controller.
FXML Based Sample
In general, for something like this for generic reuse you might create a custom control as outlined previously, but for brevity this sample will just use the in-built MediaView and Label controls rather than a custom control.
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.media.MediaView?>
<VBox maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" spacing="10.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="plot.VideoPlayerController">
<children>
<Label fx:id="progress" text="Label" />
<MediaView fx:id="mediaView" fitHeight="208.0" fitWidth="540.0" />
</children>
</VBox>
App
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class VideoPlayerApp extends Application {
#Override
public void start(final Stage stage) throws Exception {
FXMLLoader loader = new FXMLLoader(getClass().getResource("player.fxml"));
Parent root = loader.load();
stage.setScene(new Scene(root));
stage.show();
}
public static void main(String[] args) throws Exception {
launch(args);
}
}
Controller
import javafx.fxml.FXML;
import javafx.scene.control.Label;
import javafx.scene.media.Media;
import javafx.scene.media.MediaPlayer;
import javafx.scene.media.MediaView;
public class VideoPlayerController {
private static final String MEDIA_LOC =
"http://download.oracle.com/otndocs/products/javafx/oow2010-2.flv";
#FXML
MediaView mediaView;
#FXML
Label progress;
public void initialize() {
final MediaPlayer oracleVid = new MediaPlayer(
new Media(MEDIA_LOC)
);
oracleVid.currentTimeProperty().addListener(observable -> {
progress.setText(
oracleVid.getCurrentTime()
+ " / "
+ oracleVid.getTotalDuration()
);
});
mediaView.setMediaPlayer(oracleVid);
oracleVid.play();
}
}

passing a variable string through a textfield for a digital clock in java fxml

im building a stop watch with a digital and analog clock but having trouble with printing the digital clock value mainly because im unsure how to pass the string to the FXML.
why is it that when i try to us id="digitalText" for the textfield in the fxml the program fails but if i were to write it using a text="00:00" it will work properly(just with a text with 00:00 though so no updating the digital clock of course). i would have hoped giving it the id would print the value inside it.
the controller
package tds7xbstopwatchfxml;
import java.awt.TextField;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.util.Duration;
public class FXMLDocumentController implements Initializable {
#FXML
private ImageView clockFace;
#FXML
private ImageView hand;
#FXML
private TextField digitalText;
String digital;
Double rotation = 0.0;
Integer ms = 00;
Integer mm = 00;
Timeline timeline = new Timeline(
new KeyFrame(Duration.millis(1000), (ActionEvent actionEvent) -> {
updateTimer();
updateDigital();
})
);
#FXML
private void stopButton(ActionEvent event) {
timeline.stop();
}
#FXML
private void startButton(ActionEvent event) {
timeline.play();
}
#FXML
private void resetButton(ActionEvent event) {
rotation = 0.0;
ms = 0;
mm = 0;
hand.setRotate(0);
digital="00:00";
timeline.stop();
}
public void updateTimer() {
ms += 1000;
if (ms >= 60000) {
ms = 00;
mm++;
}
rotation = (ms / 60000.0) * 360.0;
hand.setRotate(rotation);
}
public void updateDigital(){
if(ms/1000<10 && mm<10){
digital=("0" + String.valueOf(mm) + ":" + "0" + String.valueOf(ms/1000));
}
if(ms/1000>=10 && mm <10){
digital=("0" + String.valueOf(mm) + ":" + "" + String.valueOf(ms/1000));
}
if(mm>=10 && ms/1000<10){
digital=("" + String.valueOf(mm) + ":" + "0" + String.valueOf(ms/1000));
}
if(mm>=10 && ms/1000>=10){
digital=("" + String.valueOf(mm) + ":" + "" + String.valueOf(ms/1000));
}
}
#Override
public void initialize(URL url, ResourceBundle rb) {
clockFace.setImage(new Image(this.getClass().getResourceAsStream("clockface.png")));
hand.setImage(new Image(this.getClass().getResourceAsStream("hand.png")));
timeline.setCycleCount(Animation.INDEFINITE);
digitalText.setText(digital);
}
}
i know there are better ways to implement the code for the digital clock but mainly i want to know about passing a changing string to be printed. the digitalText.setText(digital); will cause it to crash
and the fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.text.*?>
<?import javafx.scene.image.*?>
<?import java.lang.*?>
<?import java.net.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<AnchorPane id="AnchorPane" prefHeight="600.0" prefWidth="600.0" styleClass="mainFxmlClass" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="tds7xbstopwatchfxml.FXMLDocumentController">
<stylesheets>
<URL value="#stopwatchui.css" />
</stylesheets>
<children>
<StackPane layoutY="94.0" prefHeight="150.0" prefWidth="200.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="175.0">
<children>
<ImageView fx:id="clockFace" fitHeight="400.0" fitWidth="400.0" pickOnBounds="true" preserveRatio="true" />
<ImageView fx:id="hand" fitHeight="400.0" fitWidth="400.0" pickOnBounds="true" preserveRatio="true" />
</children>
</StackPane>
<TextField fx:id="digitalText" alignment="CENTER" editable="false" layoutX="204.0" layoutY="123.0" prefHeight="43.0" prefWidth="194.0">
<font>
<Font name="Arial" size="23.0" />
</font>
</TextField>
<Button fx:id="stopbutton" layoutX="280.0" layoutY="75.0" onAction="#stopButton" text="Stop" />
<Button fx:id="startbutton" layoutX="204.0" layoutY="75.0" onAction="#startButton" text="Start" />
<Button fx:id="resetbutton" layoutX="353.0" layoutY="75.0" onAction="#resetButton" text="Reset" />
</children>
</AnchorPane>

You imported the Swing TextField, not the JavaFX text field
Change
import java.awt.TextField
to
import java.scene.control.TextField;