We Keep Coding

java fx - different behaviour depending on context

my apologies if this is an easy thing for you, but my mind boggles. After several years of not programming at all, I am working on a pet project (2d tile based game engine) where I would like to use Java FX headless in order to make use of the graphics capabilities.
I have understood from here and here
that you need to a Java FX Application in order to have the graphics system initialized.
So I basically took the ImageViewer example and implemented Runnable:
package net.ck.game.test;
import java.io.BufferedReader;
import java.util.ArrayList;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.core.Logger;
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
public class ImageTest extends Application implements Runnable {
protected static final Logger logger = (Logger) LogManager.getLogger(ImageTest.class);
BufferedReader x;
#Override public void start(#SuppressWarnings("exports") Stage stage) {
logger.error(Thread.currentThread().getName() + ", executing run() method!");
Image standardImage = new Image("file:graphics/image1.png");
logger.error("image height image1: "+ standardImage.getHeight());
logger.error("image width image1:" + standardImage.getWidth());
Image movingImage = new Image("file:graphics/image2.png");
ArrayList<Image> images = new ArrayList<Image>();
images.add(movingImage);
images.add(standardImage);
ImageView iv1 = new ImageView();
iv1.setImage(standardImage);
ImageView iv2 = new ImageView();
iv2.setImage(movingImage);
Group root = new Group();
Scene scene = new Scene(root);
scene.setFill(Color.BLACK);
HBox box = new HBox();
box.getChildren().add(iv1);
box.getChildren().add(iv2);
root.getChildren().add(box);
stage.setTitle("ImageView");
stage.setWidth(415);
stage.setHeight(200);
stage.setScene(scene);
stage.sizeToScene();
stage.show();
}
public static void main(String[] args) {
Application.launch(args);
}
#Override
public void run()
{
Application.launch(ImageTest.class);
}
}
When I run this as its own application, this works fine and displays the two images I want it to display.
When I run it like this in the "game" constructor:
public class Game {
private boolean animated;
public boolean isAnimated() {
return animated;
}
public void setAnimated(boolean animated) {
this.animated = animated;
}
public Game() {
setAnimated(true);
if (isAnimated() == true)
{
ImageTest imageTest = new ImageTest();
new Thread(imageTest).start();
}
}
There are no errors, ImageTest runs in its own thread, the application window opens, but it is empty.
I do not understand this at all, why is that?
Can someone pleaese shed some light on this?
UPDATE:
I had different working contexts by accident. Fixing this fixed the problem.

UPDATE: I had different working contexts by accident. Fixing this fixed the problem.

How To Make An Application Icon Progress Indicator In Java? [duplicate]

I'd like to know if it is possible to make a progress bar displayed on the taskbar like Windows Explorer does when there's a file operation going on?
I saw many examples, but they all involved C#.
SWT won't cut it.

I found out that this feature is included in Java 9. It is part of AWT and it is quity simple too use.
Here is short example:
import java.awt.Taskbar;
import java.awt.Taskbar.State;
import javax.swing.JFrame;
import javax.swing.WindowConstants;
/**
* #author fxl
*/
public class TaskbarSample {
public static void main(String[] args) {
// JavaDoc:
// https://docs.oracle.com/javase/9/docs/api/java/awt/Taskbar.html
// MSDNDoc:
// https://msdn.microsoft.com/en-us/library/dd391692(VS.85).aspx
if (Taskbar.isTaskbarSupported() == false) {
return;
}
JFrame dialog = new JFrame("Test - 50%");
dialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
dialog.setVisible(true);
Taskbar taskbar = Taskbar.getTaskbar();
taskbar.setWindowProgressState(dialog, State.ERROR);
taskbar.setWindowProgressValue(dialog, 50);
}
}

this is now possible using SWT please review the code example:
org.eclipse.swt.snippets.Snippet336

This example will do the job:
Task bar:
Code:
import org.bridj.Platform;
import org.bridj.Pointer;
import org.bridj.cpp.com.COMRuntime;
import org.bridj.cpp.com.shell.ITaskbarList3;
import org.bridj.jawt.JAWTUtils;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class TaskBarListDemo extends JFrame implements ActionListener, ChangeListener
{
private ITaskbarList3 list;
private JSlider slider;
private Pointer<?> hwnd;
private TaskBarListDemo() throws ClassNotFoundException
{
super("TaskbarList Demo (" + (Platform.is64Bits() ? "64 bits" : "32 bits") + ")");
list = COMRuntime.newInstance(ITaskbarList3.class);
getContentPane().add("Center", new JLabel("Hello Native Windows 7 World !"));
Box box = Box.createVerticalBox();
int min = 0;
int max = 300;
int val = (min + max / 2);
slider = new JSlider(min, max, val);
slider.addChangeListener(this);
box.add(slider);
ButtonGroup group = new ButtonGroup();
for (ITaskbarList3.TbpFlag state : ITaskbarList3.TbpFlag.values())
{
JRadioButton cb = new JRadioButton(state.name());
group.add(cb);
cb.putClientProperty(ITaskbarList3.TbpFlag.class, state);
cb.setSelected(state == ITaskbarList3.TbpFlag.TBPF_NORMAL);
cb.addActionListener(this);
box.add(cb);
}
getContentPane().add("South", box);
}
#Override
protected void finalize() throws Throwable
{
super.finalize();
list.Release();
}
public void setVisible(boolean visible)
{
super.setVisible(visible);
long hwndVal = JAWTUtils.getNativePeerHandle(this);
hwnd = Pointer.pointerToAddress(hwndVal);
list.SetProgressValue((Pointer) hwnd, slider.getValue(), slider.getMaximum());
}
#Override
public void stateChanged(ChangeEvent actionEvent)
{
list.SetProgressValue((Pointer) hwnd, slider.getValue(), slider.getMaximum());
}
#Override
public void actionPerformed(ActionEvent actionEvent)
{
JRadioButton button = ((JRadioButton) actionEvent.getSource());
if (button.isSelected())
{
ITaskbarList3.TbpFlag flag = (ITaskbarList3.TbpFlag) button.getClientProperty(ITaskbarList3.TbpFlag.class);
list.SetProgressValue((Pointer) hwnd, slider.getValue(), slider.getMaximum());
list.SetProgressState((Pointer) hwnd, flag);
}
}
public static void main(String[] arguments) throws Exception
{
TaskBarListDemo f = new TaskBarListDemo();
f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
f.pack();
f.setVisible(true);
}
}
Maven dependencies:
<dependencies>
<dependency>
<groupId>com.nativelibs4java</groupId>
<artifactId>bridj</artifactId>
<version>LATEST</version>
</dependency>
<dependency>
<groupId>net.java.dev.jna</groupId>
<artifactId>jna</artifactId>
<version>LATEST</version>
</dependency>
<dependency>
<groupId>net.java.dev.jna</groupId>
<artifactId>jna-platform</artifactId>
<version>LATEST</version>
</dependency>
</dependencies>

There is no standard facility in Java for doing so, yet.
Hence you need to talk to Windows directly to do that. So you need to locate the correct Windows routine, and use JNA (probably the easiest) to invoke that routine. I do not know of a vendor or a project who has done this already.
Edit: It appears that the http://code.google.com/p/nativelibs4java/ project may do what you want.

As Java9's java.awt.Taskbar only works for old swing frames (they somehow forgot to implement this for javafx.stage.Stage) and com.nativelibs4java bridj isn't working (anymore) (see https://github.com/nativelibs4java/BridJ/issues/94) I implemented a solution using JNA 4.1.0.
Please note:
Relies on calling internal javafx api (com.sun.javafx.stage.WindowHelper) - so it might break with the next java update
It only sets the "indeterminate" progress state - but normal progress state should be possible too with some adjustments
Hope this helps.
ITaskbarList3.java
package example;
import com.sun.jna.platform.win32.Guid.IID;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.platform.win32.WinNT.HRESULT;
public interface ITaskbarList3 {
IID IID_ITASKBARLIST3 = new IID("ea1afb91-9e28-4b86-90e9-9e9f8a5eefaf"); // from ShObjIdl.h
int TBPF_NOPROGRESS = 0;
int TBPF_INDETERMINATE = 0x1;
int TBPF_NORMAL = 0x2;
int TBPF_ERROR = 0x4;
int TBPF_PAUSED = 0x8;
HRESULT SetProgressState(HWND hwnd, int tbpFlags);
}
TaskbarList3.java
package example;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.platform.win32.WinNT.HRESULT;
import com.sun.jna.platform.win32.COM.COMInvoker;
public final class TaskbarList3 extends COMInvoker implements ITaskbarList3 {
public TaskbarList3(Pointer pointer) {
setPointer(pointer);
}
#Override
public HRESULT SetProgressState(HWND hwnd, int tbpFlags) {
return (HRESULT) this._invokeNativeObject(
10, // magic number (gathered by trial and error)
new Object[] { this.getPointer(), hwnd, tbpFlags },
HRESULT.class);
}
}
TaskbarPeer.java
package example;
import com.sun.javafx.stage.WindowHelper;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.Guid.CLSID;
import com.sun.jna.platform.win32.Ole32;
import com.sun.jna.platform.win32.W32Errors;
import com.sun.jna.platform.win32.WTypes;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.ptr.PointerByReference;
import javafx.stage.Stage;
public final class TaskbarPeer {
public static void setIndeterminateProgress(Stage stage, boolean indeterminate) {
final var peer = WindowHelper.getPeer(stage);
final long windowHandle = peer.getRawHandle();
final var clsid = new CLSID("56FDF344-FD6D-11d0-958A-006097C9A090"); // from ShObjIdl.h
final var taskbarListPointerRef = new PointerByReference();
var hr = Ole32.INSTANCE.CoCreateInstance(clsid, null, WTypes.CLSCTX_SERVER,
ITaskbarList3.IID_ITASKBARLIST3, taskbarListPointerRef);
if (W32Errors.FAILED(hr)) {
throw new RuntimeException("failed with code: " + hr.intValue());
}
final TaskbarList3 taskbarList = new TaskbarList3(taskbarListPointerRef.getValue());
final var hwnd = new HWND(new Pointer(windowHandle));
final int progressState = indeterminate ? ITaskbarList3.TBPF_INDETERMINATE : ITaskbarList3.TBPF_NOPROGRESS;
hr = taskbarList.SetProgressState(hwnd, progressState);
if (W32Errors.FAILED(hr)) {
throw new RuntimeException("failed with code: " + hr.intValue());
}
}
}
Sample.java
package example;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.stage.Stage;
public final class Sample extends Application {
private boolean indeterminateProgressState = false;
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
final Button btn = new Button("Click me!");
primaryStage.setScene(new Scene(btn));
primaryStage.sizeToScene();
primaryStage.show();
btn.setOnAction(evt -> {
indeterminateProgressState = !indeterminateProgressState;
TaskbarPeer.setIndeterminateProgress(primaryStage, indeterminateProgressState);
});
}
}

Windows exposes this through COM. I am sure a "flat DLL" call would be easier for you, but if you can get to COM you can do this. The COM interface is ITaskbarList3 (there is also an ITaskbarList4 you can use that inherits from it.) http://msdn.microsoft.com/en-us/library/dd391692(VS.85).aspx documents it. SetProgressState and SetProgressValue are the methods you will want to invoke. State is normal (green), paused (yellow), error (red), indeterminate (swooshing green) and none. On the MSDN page some community people have added details of calling this COM component from VB and C# - that might help you figure out the setup and tear down required from Java.

Exception in thread "LWJGL Application" java.lang.NullPointerException

I am following a tutorial on creating a game with LibGdx from some ebook. the tutorial has steps for creating a game called "Canyon Bunny". Its a simple 2D game. but i keep getting this annoying error! (i also used to get the error on a different tutorial of the same genre)
i am in the early stages of the development for this game. and i am doing some test (of which i follow to the letter from the tutorial). I use a MAC and a i have tried many solutions with no luck at all.
Exception in thread "LWJGL Application" java.lang.NullPointerException
at com.Adel.CanyonBunny.game.WorldUpdater.updateTestObjects(WorldUpdater.java:83)
at com.Adel.CanyonBunny.game.WorldUpdater.update(WorldUpdater.java:76)
at com.Adel.CanyonBunny.CanyonBunnyMain.render(CanyonBunnyMain.java:39)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:207)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114)
It is truly one of the most frustrating things a striving programmer can face.
ill get the code of all the classes in case that's related somehow...
This is CanyonBunnyMain in the general program:
package com.Adel.CanyonBunny;
import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.Texture.TextureFilter;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.graphics.g2d.TextureRegion;
import com.Adel.CanyonBunny.game.*;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.Application;
public class CanyonBunnyMain implements ApplicationListener {
private static final String TAG = CanyonBunnyMain.class.getName();
private WorldUpdater worldUpdater;
private WorldRenderer worldRenderer ;
private boolean paused ;
public void create() {
//I'll set the log to debug for the developing process
Gdx.app.setLogLevel(Application.LOG_DEBUG) ;
worldUpdater = new WorldUpdater();
worldRenderer = new WorldRenderer() ;
// since, upon creation, the game is not paused, then:
paused = false ;
}
public void render() {
if (paused = true) {
//update the game by the time passed since the last update
worldUpdater.update(Gdx.graphics.getDeltaTime()) ;
}
//sets the screen color to: CornFlower Blue
Gdx.gl.glClearColor(0x64 / 255.0f, 0x95 / 255.0f, 0xed / 255.0f, 0xff / 255.0f);
//clears the screen to prevent flickering
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT) ;
//Render the game to the screen
worldRenderer.render();
}
public void resize (int w, int h) {
worldRenderer.resize(w, h) ;
}
public void pause () {
paused = true ;
}
public void resume() {
paused = false ;
}
public void dispose() {
worldRenderer.dispose() ;
} }
this is the WorldRenderer (general program too) :
package com.Adel.CanyonBunny.game;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.Pixmap;
import com.badlogic.gdx.graphics.Pixmap.Format;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.math.MathUtils;
public class WorldRenderer {
private OrthographicCamera cam;
private SpriteBatch batch ;
private WorldUpdater updater;
public void WorldRenderer(WorldUpdater worldUpdater) { }
public void init() { }
public void render() { }
public void resize(int w, int h) { }
public void dispose() { }
}
this is the main class (from the desktop project: the one that i run on my MAC) :
package com.Adel.CanyonBunny;
import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;
public class Main {
public static void main(String[] args) {
LwjglApplicationConfiguration cfg = new LwjglApplicationConfiguration();
cfg.title = "CanyonBunny";
cfg.useGL20 = false;
cfg.width = 800;
cfg.height = 480;
new LwjglApplication(new CanyonBunnyMain(), cfg);
}
}
Any help will be wonderful.
tell me should you need extra data
this is the WorldUpdater class for those who asked:
package com.Adel.CanyonBunny.game;
import com.badlogic.gdx.graphics.Pixmap;
import com.badlogic.gdx.graphics.Pixmap.Format;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.math.MathUtils;
public class WorldUpdater {
private final String TAG = WorldUpdater.class.getName();
public Sprite[] testSprites;
public int selectedSprite;
public WorldRenderer worldRenderer;
public void worldUpdater() {
init() ;
}
public void init() {
initTestObjects() ;
}
private void initTestObjects() {
// create new array of 5 sprites
testSprites = new Sprite[5] ;
// Create empty POT-sized Pixmap with 8 bit RGBA pixel data
int w = 32;
int h = 32;
Pixmap pixmap = createProceduralPixmap(w, h) ;
//create a new texture from Pixmap data
Texture texture = new Texture(pixmap) ;
//create sprites using the just created texture
for (int i = 0; i < testSprites.length; i++) {
Sprite spr = new Sprite(texture) ;
spr.setSize(1,1) ;
//set origin to sprite's center
spr.setOrigin(spr.getWidth() / 2.0f, spr.getHeight() / 2.0f) ;
float randomX = MathUtils.random(-2.0f, 2.0f) ;
float randomY = MathUtils.random(-2.0f, 2.0f) ;
spr.setPosition(randomX, randomY) ;
//put new sprite into array
testSprites[i] = spr ;
}
//set first sprite as the selected one
selectedSprite = 0 ;
}
private Pixmap createProceduralPixmap(int width, int height) {
Pixmap pixmap = new Pixmap(width, height , Format.RGBA8888) ;
//fill the square with red color at 50% opacity
pixmap.setColor(1, 0, 0, 0.5f) ;
pixmap.fill() ;
//draw a yellow X in the pixmap
pixmap.setColor(1, 1, 0 , 1) ;
pixmap.drawLine(0, 0, width, height) ;
pixmap.drawLine(width, 0, 0, height);
//draw a cyan-colored border around the square
pixmap.setColor(0, 1, 1, 1) ;
pixmap.drawRectangle(0, 0, width, height) ;
return pixmap;
}
public void update(float deltaTime) {
updateTestObjects(deltaTime);
}
private void updateTestObjects(float deltaTime) {
//get current rotation from the selected sprite
float rotation = testSprites[selectedSprite].getRotation();
//rotate sprite by 90 degrees per second
rotation += 90 * deltaTime;
//wrap around at 360 degrees
rotation %= 360 ;
testSprites[selectedSprite].setRotation(rotation);
}
}
Also, when i check this line out in Debugging mode:
testSprites = new Sprite[5] ;
"testSprites" keeps showing null.
i hope this clears up some details!
thanks again.

The problem is with your "constructors", mainly in the updater (as the renderer does nothing):
public void worldUpdater() { ... }
Constructors should not specify return types - that's part of how the compiler recognizes them as constructors. As it is in your code, it's just a method you could call on an existing object instance. Change it like so:
public WorldUpdater() { ... }
Note the lack of a return type and the uppercase W.
You can change the renderer the same way. (But then you will have to pass the updater to its constructor in the main class.)
Also, Nine Magics is right that the way you store renderer and updater references in each other doesn't make much sense, even if it's not related to this problem. I see no reason why an updater class would need to know about its renderer, I'd remove that field.

In your WorldRenderer you specify this:
public void WorldRenderer(WorldUpdater worldUpdater) { }
And WorldRendere also carries an instance of an worldUpdater?
private WorldUpdater updater;
But on your main file you create an instance of both renderer and updater?
worldUpdater = new WorldUpdater();
worldRenderer = new WorldRenderer() ;
I don't know, I might have tired eyes or something but this seems too complex. Can it be that you are refering to a wrong instance of WorldUpdater? Might edit this if I can wrap my head around it better.

store images and display in different classes

I'm trying to get mutiple images in 'GetImage' class, and disply them in the main class.
Can anybody show me an example how to do it?? I tried bunch of other samples but they didn't work since I have two classes.
Here is one that I tried.
main clss:
import java.awt.*;
import hsa.*;
public class Test
{
static Console c;
public void Display()
{
GetImage c = new GetImage();
c.paint(g);
}
public Test()
{
c = new Console ();
}
public static void main (String[] args) throws Exception
{
Test = new Test();
a.Display();
}
}
seperate class:
import java.awt.*;
import hsa.Console;
import java.awt.event.*;
public class GetImage extends Frame
{
Image image;
String imageName = "ImageFileName.jpg";
public void paint (Graphics g)
{
Toolkit tool = Toolkit.getDefaultToolkit ();
image = tool.getImage (imageName);
g.drawImage (image, 30, 30, this); // location of the image
g.drawString (imageName, 100, 50); // location of the name
}
}

I'm not very familiar with the hsa package, but some quick googling says it's an educational package from some company that has since gone out of business, correct me if I'm wrong. So personally I'd try to avoid using any of their stuff if you can.
If you have to use this for school or something then you probably want to stick entirely with their package instead of mix and matching hsa with awt. Something like this might accomplish what you want, but again I'm not familiar with the hsa package.
import java.awt.*;
import hsa.*;
public class Test
{
static Console c;
public void Display()
{
GetImage gI = new GetImage(c,25,80,12);
}
public Test()
{
c = new Console ();
}
public static void main (String[] args) throws Exception
{
Test = new Test();
a.Display();
}
}
import java.awt.*;
import hsa.ConsoleCanvasGraphics;
import java.awt.event.*;
public class GetImage extends ConsoleCanvasGraphics
{
Image image, image2;
String imageName = "ImageFileName.jpg", image2Name = "Image2FileName.jpg";
public GetImage(ConsoleParent parent, int rows, int columns, int fontSize)
{
Toolkit tool = Toolkit.getDefaultToolkit ();
image = tool.getImage (imageName);
image2 = tool.getImage (image2Name);
super(parent,rows,columns,fontSize);
drawImage(image,30,30,this);
drawImage(image2,30,60,this);
drawString(imageName,100,50,new Font("TimesRoman", Font.PLAIN, 20),Color.BLACK);
drawString(image2Name,100,80,new Font("TimesRoman", Font.PLAIN, 20),Color.BLACK);
}
}
Again, I'd try to avoid hsa myself, but if you're set on using it and need to have two separate classes in your program then the above should be a rough outline of something that might work.

Windows 7 Taskbar Progress Bar in Java

I'd like to know if it is possible to make a progress bar displayed on the taskbar like Windows Explorer does when there's a file operation going on?
I saw many examples, but they all involved C#.
SWT won't cut it.

I found out that this feature is included in Java 9. It is part of AWT and it is quity simple too use.
Here is short example:
import java.awt.Taskbar;
import java.awt.Taskbar.State;
import javax.swing.JFrame;
import javax.swing.WindowConstants;
/**
* #author fxl
*/
public class TaskbarSample {
public static void main(String[] args) {
// JavaDoc:
// https://docs.oracle.com/javase/9/docs/api/java/awt/Taskbar.html
// MSDNDoc:
// https://msdn.microsoft.com/en-us/library/dd391692(VS.85).aspx
if (Taskbar.isTaskbarSupported() == false) {
return;
}
JFrame dialog = new JFrame("Test - 50%");
dialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
dialog.setVisible(true);
Taskbar taskbar = Taskbar.getTaskbar();
taskbar.setWindowProgressState(dialog, State.ERROR);
taskbar.setWindowProgressValue(dialog, 50);
}
}

this is now possible using SWT please review the code example:
org.eclipse.swt.snippets.Snippet336

This example will do the job:
Task bar:
Code:
import org.bridj.Platform;
import org.bridj.Pointer;
import org.bridj.cpp.com.COMRuntime;
import org.bridj.cpp.com.shell.ITaskbarList3;
import org.bridj.jawt.JAWTUtils;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class TaskBarListDemo extends JFrame implements ActionListener, ChangeListener
{
private ITaskbarList3 list;
private JSlider slider;
private Pointer<?> hwnd;
private TaskBarListDemo() throws ClassNotFoundException
{
super("TaskbarList Demo (" + (Platform.is64Bits() ? "64 bits" : "32 bits") + ")");
list = COMRuntime.newInstance(ITaskbarList3.class);
getContentPane().add("Center", new JLabel("Hello Native Windows 7 World !"));
Box box = Box.createVerticalBox();
int min = 0;
int max = 300;
int val = (min + max / 2);
slider = new JSlider(min, max, val);
slider.addChangeListener(this);
box.add(slider);
ButtonGroup group = new ButtonGroup();
for (ITaskbarList3.TbpFlag state : ITaskbarList3.TbpFlag.values())
{
JRadioButton cb = new JRadioButton(state.name());
group.add(cb);
cb.putClientProperty(ITaskbarList3.TbpFlag.class, state);
cb.setSelected(state == ITaskbarList3.TbpFlag.TBPF_NORMAL);
cb.addActionListener(this);
box.add(cb);
}
getContentPane().add("South", box);
}
#Override
protected void finalize() throws Throwable
{
super.finalize();
list.Release();
}
public void setVisible(boolean visible)
{
super.setVisible(visible);
long hwndVal = JAWTUtils.getNativePeerHandle(this);
hwnd = Pointer.pointerToAddress(hwndVal);
list.SetProgressValue((Pointer) hwnd, slider.getValue(), slider.getMaximum());
}
#Override
public void stateChanged(ChangeEvent actionEvent)
{
list.SetProgressValue((Pointer) hwnd, slider.getValue(), slider.getMaximum());
}
#Override
public void actionPerformed(ActionEvent actionEvent)
{
JRadioButton button = ((JRadioButton) actionEvent.getSource());
if (button.isSelected())
{
ITaskbarList3.TbpFlag flag = (ITaskbarList3.TbpFlag) button.getClientProperty(ITaskbarList3.TbpFlag.class);
list.SetProgressValue((Pointer) hwnd, slider.getValue(), slider.getMaximum());
list.SetProgressState((Pointer) hwnd, flag);
}
}
public static void main(String[] arguments) throws Exception
{
TaskBarListDemo f = new TaskBarListDemo();
f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
f.pack();
f.setVisible(true);
}
}
Maven dependencies:
<dependencies>
<dependency>
<groupId>com.nativelibs4java</groupId>
<artifactId>bridj</artifactId>
<version>LATEST</version>
</dependency>
<dependency>
<groupId>net.java.dev.jna</groupId>
<artifactId>jna</artifactId>
<version>LATEST</version>
</dependency>
<dependency>
<groupId>net.java.dev.jna</groupId>
<artifactId>jna-platform</artifactId>
<version>LATEST</version>
</dependency>
</dependencies>

There is no standard facility in Java for doing so, yet.
Hence you need to talk to Windows directly to do that. So you need to locate the correct Windows routine, and use JNA (probably the easiest) to invoke that routine. I do not know of a vendor or a project who has done this already.
Edit: It appears that the http://code.google.com/p/nativelibs4java/ project may do what you want.

As Java9's java.awt.Taskbar only works for old swing frames (they somehow forgot to implement this for javafx.stage.Stage) and com.nativelibs4java bridj isn't working (anymore) (see https://github.com/nativelibs4java/BridJ/issues/94) I implemented a solution using JNA 4.1.0.
Please note:
Relies on calling internal javafx api (com.sun.javafx.stage.WindowHelper) - so it might break with the next java update
It only sets the "indeterminate" progress state - but normal progress state should be possible too with some adjustments
Hope this helps.
ITaskbarList3.java
package example;
import com.sun.jna.platform.win32.Guid.IID;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.platform.win32.WinNT.HRESULT;
public interface ITaskbarList3 {
IID IID_ITASKBARLIST3 = new IID("ea1afb91-9e28-4b86-90e9-9e9f8a5eefaf"); // from ShObjIdl.h
int TBPF_NOPROGRESS = 0;
int TBPF_INDETERMINATE = 0x1;
int TBPF_NORMAL = 0x2;
int TBPF_ERROR = 0x4;
int TBPF_PAUSED = 0x8;
HRESULT SetProgressState(HWND hwnd, int tbpFlags);
}
TaskbarList3.java
package example;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.platform.win32.WinNT.HRESULT;
import com.sun.jna.platform.win32.COM.COMInvoker;
public final class TaskbarList3 extends COMInvoker implements ITaskbarList3 {
public TaskbarList3(Pointer pointer) {
setPointer(pointer);
}
#Override
public HRESULT SetProgressState(HWND hwnd, int tbpFlags) {
return (HRESULT) this._invokeNativeObject(
10, // magic number (gathered by trial and error)
new Object[] { this.getPointer(), hwnd, tbpFlags },
HRESULT.class);
}
}
TaskbarPeer.java
package example;
import com.sun.javafx.stage.WindowHelper;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.Guid.CLSID;
import com.sun.jna.platform.win32.Ole32;
import com.sun.jna.platform.win32.W32Errors;
import com.sun.jna.platform.win32.WTypes;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.ptr.PointerByReference;
import javafx.stage.Stage;
public final class TaskbarPeer {
public static void setIndeterminateProgress(Stage stage, boolean indeterminate) {
final var peer = WindowHelper.getPeer(stage);
final long windowHandle = peer.getRawHandle();
final var clsid = new CLSID("56FDF344-FD6D-11d0-958A-006097C9A090"); // from ShObjIdl.h
final var taskbarListPointerRef = new PointerByReference();
var hr = Ole32.INSTANCE.CoCreateInstance(clsid, null, WTypes.CLSCTX_SERVER,
ITaskbarList3.IID_ITASKBARLIST3, taskbarListPointerRef);
if (W32Errors.FAILED(hr)) {
throw new RuntimeException("failed with code: " + hr.intValue());
}
final TaskbarList3 taskbarList = new TaskbarList3(taskbarListPointerRef.getValue());
final var hwnd = new HWND(new Pointer(windowHandle));
final int progressState = indeterminate ? ITaskbarList3.TBPF_INDETERMINATE : ITaskbarList3.TBPF_NOPROGRESS;
hr = taskbarList.SetProgressState(hwnd, progressState);
if (W32Errors.FAILED(hr)) {
throw new RuntimeException("failed with code: " + hr.intValue());
}
}
}
Sample.java
package example;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.stage.Stage;
public final class Sample extends Application {
private boolean indeterminateProgressState = false;
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
final Button btn = new Button("Click me!");
primaryStage.setScene(new Scene(btn));
primaryStage.sizeToScene();
primaryStage.show();
btn.setOnAction(evt -> {
indeterminateProgressState = !indeterminateProgressState;
TaskbarPeer.setIndeterminateProgress(primaryStage, indeterminateProgressState);
});
}
}

Windows exposes this through COM. I am sure a "flat DLL" call would be easier for you, but if you can get to COM you can do this. The COM interface is ITaskbarList3 (there is also an ITaskbarList4 you can use that inherits from it.) http://msdn.microsoft.com/en-us/library/dd391692(VS.85).aspx documents it. SetProgressState and SetProgressValue are the methods you will want to invoke. State is normal (green), paused (yellow), error (red), indeterminate (swooshing green) and none. On the MSDN page some community people have added details of calling this COM component from VB and C# - that might help you figure out the setup and tear down required from Java.