Develop Reference

Java Swing: Making a growing circle by mouse click on JPanel

I'm a beginner in Java and this time I'm trying to learn more by finding code examples and editing them, for example from this website. I have a JFrame and each time it (or more precise the JPanel in it) is clicked on, a circle is drawn which will grow/expand outwards like a water ripple. Each circle starts with a certain radius and will be removed or redrawn when reaching a bigger radius (I chose radius "r" from 10 to 200). I have two programs for this which almost work but are missing something. If I'm correct, I might also know what their problems are but I can't figure out how to solve them:
One generates growing circles but all of them have the same size, no matter when they're generated, since I can't find out how to assign the radius to a single circle. The code is adapted from here:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
public class Ripples extends JPanel implements ActionListener{
public int r = 10;
private ArrayList<Point> p;
public Ripples() {
p = new ArrayList<>();
addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
p.add(new Point(e.getX(), e.getY()));
}
});
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setColor(Color.CYAN);
for (Point pt : p) {
g2.drawOval(pt.x-r, pt.y-r, 2*r, 2*r);
}
}
#Override
public void actionPerformed(ActionEvent evt) {
if(r<200){
r++;
} else {
r = 10;
}
repaint();
}
public static void Gui() {
JFrame f = new JFrame();
Ripples p = new Ripples();
p.setBackground(Color.WHITE);
f.setContentPane(p);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(500,300);
f.setVisible(true);
Timer t = new Timer(20,p);
t.start();
}
public static void main(String[] args) {
Gui();
}
}
The other program(I've forgotten where I got it from) has circles with different radii depending on when they were generated, however the circles "flicker", because -as far as I understand- they are all processed at the same time, because the code doesn't include an Array to store and update each circle individually like the one above does:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
public class Ripples extends JPanel {
int x,y;
int r = 10;
public Ripples(int x, int y) {
this.x = x;
this.y = y;
Timer t = new Timer(20, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (r<200) {
r++;
} else {
r=10;
}
revalidate();
repaint();
}
});
t.start();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.CYAN);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.drawOval(x-r,y-r,2*r,2*r);
}
public static void Gui() {
JFrame f = new JFrame("Water Ripples");
JPanel p0 = new JPanel();
p0.setBackground(Color.WHITE);
f.add(p0);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setBounds(100,100,600,500);
f.setVisible(true);
f.addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
Ripples rG = new Ripples(e.getX(), e.getY());
rG.setBackground(Color.WHITE);
f.add(rG);
}
});
}
public static void main(String[] args) {
Gui();
}
}
So how can I solve this so that I get the circles growing independent from each other? I'd prefer a solution/improvement/hint for the upper code because I think its structured better than the second one. Also, I apologize for not splitting the code into more classes and for possibly not sticking to naming conventions. I appreciate your help, thank you very much!

I added a Circle class to your Ripples code. This allows the ActionListener to treat each circle independently.
I started the GUI with a call to the SwingUtilities invokeLater method. This method ensures that the Swing components are created and executed on the Event Dispatch Thread.
Here's the code.
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class Ripples extends JPanel implements ActionListener {
private List<Circle> circles;
public Ripples() {
circles = new ArrayList<>();
addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent event) {
circles.add(new Circle(event.getPoint()));
}
});
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setColor(Color.CYAN);
g2.setStroke(new BasicStroke(3f));
for (Circle circle : circles) {
Point p = circle.getCenter();
int radius = circle.getRadius();
g2.drawOval(p.x - radius, p.y - radius,
2 * radius, 2 * radius);
}
}
#Override
public void actionPerformed(ActionEvent evt) {
for (Circle circle : circles) {
circle.incrementRadius();
}
repaint();
}
public static void createGUI() {
JFrame f = new JFrame("Ripples");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Ripples p = new Ripples();
p.setBackground(Color.WHITE);
p.setPreferredSize(new Dimension(500, 500));
f.setContentPane(p);
f.pack();
f.setLocationByPlatform(true);
f.setVisible(true);
Timer t = new Timer(20, p);
t.start();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
createGUI();
}
});
}
public class Circle {
private int radius;
private final Point center;
public Circle(Point center) {
this.center = center;
this.radius = 10;
}
public void incrementRadius() {
radius += 1;
radius = (radius > 200) ? 10 : radius;
}
public int getRadius() {
return radius;
}
public Point getCenter() {
return center;
}
}
}
Edited to add:
I reworked the Ripples class code to separate the concerns. I created a DrawingPanel class to hold the drawing panel, a RipplesListener class to hold the MouseAdapter code, an Animation class to hold the Runnable that runs the animation of the circles, a RipplesModel class to hold the List of Circle instances, and finally, the Circle class.
I could have used a Swing Timer for the animation, but I'm more familiar with creating and running my own animation thread.
Yes, this code is more complicated than the original example. The coding style used here can be carried into larger, more complex Swing GUI development.
Here's the revised code. I hope it's a better example.
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Ripples implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Ripples());
}
private Animation animation;
private DrawingPanel drawingPanel;
private RipplesModel model;
public Ripples() {
model = new RipplesModel();
}
#Override
public void run() {
JFrame frame = new JFrame("Ripples");
frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
frame.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent event) {
stopAnimation();
frame.dispose();
System.exit(0);
}
});
drawingPanel = new DrawingPanel(model);
frame.add(drawingPanel, BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
animation = new Animation(this, model);
new Thread(animation).start();
}
public void repaint() {
drawingPanel.repaint();
}
private void stopAnimation() {
if (animation != null) {
animation.setRunning(false);
}
}
public class DrawingPanel extends JPanel {
private static final long serialVersionUID = 1L;
private RipplesModel model;
public DrawingPanel(RipplesModel model) {
this.model = model;
setBackground(Color.WHITE);
setPreferredSize(new Dimension(500, 500));
addMouseListener(new RipplesListener(model));
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(new BasicStroke(3f));
List<Circle> circles = model.getCircles();
for (Circle circle : circles) {
Point p = circle.getCenter();
int radius = circle.getRadius();
g2.setColor(circle.getColor());
g2.drawOval(p.x - radius, p.y - radius,
2 * radius, 2 * radius);
}
}
}
public class RipplesListener extends MouseAdapter {
private RipplesModel model;
public RipplesListener(RipplesModel model) {
this.model = model;
}
#Override
public void mousePressed(MouseEvent event) {
model.addCircle(new Circle(event.getPoint(),
createColor()));
}
private Color createColor() {
Random random = new Random();
int r = random.nextInt(255);
int g = random.nextInt(255);
int b = random.nextInt(255);
return new Color(r, g, b);
}
}
public class Animation implements Runnable {
private volatile boolean running;
private Ripples frame;
private RipplesModel model;
public Animation(Ripples frame, RipplesModel model) {
this.frame = frame;
this.model = model;
this.running = true;
}
#Override
public void run() {
while (running) {
sleep(20L);
incrementRadius();
}
}
private void incrementRadius() {
List<Circle> circles = model.getCircles();
for (Circle circle : circles) {
circle.incrementRadius();
}
repaint();
}
private void sleep(long delay) {
try {
Thread.sleep(delay);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private void repaint() {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
frame.repaint();
}
});
}
public synchronized void setRunning(boolean running) {
this.running = running;
}
}
public class RipplesModel {
private List<Circle> circles;
public RipplesModel() {
this.circles = new ArrayList<>();
}
public void addCircle(Circle circle) {
this.circles.add(circle);
}
public List<Circle> getCircles() {
return circles;
}
}
public class Circle {
private int radius;
private final Color color;
private final Point center;
public Circle(Point center, Color color) {
this.center = center;
this.color = color;
this.radius = 10;
}
public void incrementRadius() {
radius = (++radius > 200) ? 10 : radius;
}
public Color getColor() {
return color;
}
public int getRadius() {
return radius;
}
public Point getCenter() {
return center;
}
}
}

I'd prefer a solution/improvement/hint for the upper code
The second code is better because it uses:
a custom class to contain information about the object to be painted
an ArrayList to contain the objects to be painted
a Timer for the animation.
because I think its structured better than the second one.
Not a good reason. Use the code that provides the functionality that you require.
Restructure the code yourself. That is part of the learning experience.
Issues with the second code:
It doesn't compile. Why post code that doesn't compile? This implies you haven't even tested it.
the initial radius is assigned when the Position object is created.
When the Timer fires you need to iterate through the ArrayList to update the radius of each Position object.
The radius of the Position object is used in the painting code.
As an added change, maybe call the Position class Ripple. Then you can add another custom property for the Color of the ripple. Then when you add the Ripple to the ArrayList you randomly generate a Color. Then in the painting method you use the Color property of the Ripple class. This is how you make objects and painting more flexible and dynamic.

Updating a rotated JLabel using Graphics2D causes old and new text to merge together

I am trying to rotate a JLabel 90 degrees that shows the current time 90 degrees. After doing some research, most people have recommended using Graphics2D and AffineTransform. This almost works, but when the minute in the time is updated, the new digit appears to merge with the old digit.
This does not happen for the seconds. Does anybody have any idea how to fix this issue or have an alternate solution?
Driver class:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.DisplayMode;
import java.awt.Font;
import java.awt.Toolkit;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
#SuppressWarnings("serial")
public class Driver extends JFrame implements KeyListener {
private boolean running = true;
ClockWidget clockWidget;
static Dimension screenSize;
public static void main(String[] args) {
screenSize = Toolkit.getDefaultToolkit().getScreenSize();
DisplayMode displayMode = new DisplayMode((int) screenSize.getWidth(), (int) screenSize.getHeight(), 32,
DisplayMode.REFRESH_RATE_UNKNOWN);
new Driver().run(displayMode);
}
public void run(DisplayMode displayMode) {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(null);
getContentPane().setBackground(Color.BLACK);
setFont(new Font("Arial", Font.PLAIN, 24));
Screen screen = new Screen();
screen.setFullScreen(displayMode, this);
initClockWidgit();
addKeyListener(this);
System.out.println("RUNNING");
while (running) {
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
quitProgram(screen);
return;
}
public void initClockWidgit() {
clockWidget = new ClockWidget();
clockWidget.setFont(new Font("Arial", Font.PLAIN, 36));
clockWidget.setForeground(Color.WHITE);
clockWidget.setBackground(Color.BLUE);
clockWidget.setBounds((int) (screenSize.getWidth() * 0.90), (int) (screenSize.getHeight() * 0.10), 250, 100);
add(clockWidget);
new Thread(clockWidget).start();
}
public void quitProgram(Screen screen) {
screen.restoreScreen();
clockWidget.disable();
}
#Override
public void keyPressed(KeyEvent keyEvent) {
int keyCode = keyEvent.getKeyCode();
if (keyCode == KeyEvent.VK_SPACE) {
running = false;
}
keyEvent.consume();
}
#Override
public void keyReleased(KeyEvent keyEvent) {
keyEvent.consume();
}
#Override
public void keyTyped(KeyEvent keyEvent) {
keyEvent.consume();
}
}
ClockWidget Class:
import java.text.SimpleDateFormat;
import java.util.Calendar;
import javax.swing.JLabel;
public class ClockWidget extends RotatedJLabel implements Runnable{
private String currentTime;
private boolean running;
public ClockWidget() {
running = true;
}
#Override
public void run() {
while(running) {
Calendar calendar = Calendar.getInstance();
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("hh:mm:ss a");
currentTime = simpleDateFormat.format(calendar.getTime());
setText(currentTime);
}
}
public void disable() {
running = false;
}
}
RotatedJLabel Class:
[import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.geom.AffineTransform;
import javax.swing.Icon;
import javax.swing.JLabel;
public class RotatedJLabel extends JLabel {
public RotatedJLabel() {
super();
}
public RotatedJLabel(Icon image) {
super(image);
}
public RotatedJLabel(Icon image, int horizontalAlignment) {
super(image, horizontalAlignment);
}
public RotatedJLabel(String text) {
super(text);
}
public RotatedJLabel(String text, Icon icon, int horizontalAlignment) {
super(text, icon, horizontalAlignment);
}
public RotatedJLabel(String text, int horizontalAlignment) {
super(text, horizontalAlignment);
}
#Override
protected void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
AffineTransform aT = g2.getTransform();
Shape oldshape = g2.getClip();
double x = getWidth()/2.0;
double y = getHeight()/2.0;
aT.rotate(Math.toRadians(90), x, y);
g2.setTransform(aT);
g2.setClip(oldshape);
super.paintComponent(g);
}
}

A few things jump out at me:
I wouldn't use a JLabel for this purpose, it's a complicate component, starting with a JPanel and simply painting the text would be simpler. In my testing it was very hard to get the sizing hints to work correctly when the graphics context was rotated.
You're not managing the component's "new" sizing hints, this could be an issue when coupled with more complex layouts, as the width of the component should now be the height and visa-versa
I'd recommend the key bindings API over KeyListener
Swing is NOT thread safe, updating the UI from outside the context of the UI could produce any number of issues; instead of using a Thread, you should be using a Swing Timer, and since you probably really only want to update the seconds, running it at a much slower speed. See Concurrency in Swing and How to Use Swing Timers for more details
And Calendar and Date are effectively deprecated. See Standard Calendar for more details
For example...
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private RotatedLabel timeLabel;
private DateTimeFormatter formatter = DateTimeFormatter.ofPattern("hh:mm:ss a");
public TestPane() {
setLayout(new GridBagLayout());
timeLabel = new RotatedLabel(currentTime());
add(timeLabel);
Timer timer = new Timer(500, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
timeLabel.setText(currentTime());
}
});
timer.start();
}
public String currentTime() {
LocalTime lt = LocalTime.now();
return lt.format(formatter);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
public class RotatedLabel extends JPanel {
private String text;
public RotatedLabel() {
super();
setOpaque(false);
setFont(UIManager.getDefaults().getFont("label.font"));
}
public RotatedLabel(String text) {
this();
this.text = text;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
revalidate();
repaint();
}
protected Dimension getTextBounds() {
FontMetrics fm = getFontMetrics(getFont());
return new Dimension(fm.stringWidth(text), fm.getHeight());
}
#Override
public Dimension getPreferredSize() {
Dimension size = getTextBounds();
return new Dimension(size.height, size.width);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
AffineTransform aT = g2.getTransform();
double x = getWidth() / 2.0;
double y = getHeight() / 2.0;
aT.rotate(Math.toRadians(90), x, y);
g2.setTransform(aT);
FontMetrics fm = g2.getFontMetrics();
float xPos = (getWidth() - fm.stringWidth(getText())) / 2.0f;
float yPos = ((getHeight() - fm.getHeight()) / 2.0f) + fm.getAscent();
g2.drawString(text, xPos, yPos);
g2.dispose();
}
}
}
Now, if you "absolutely, must, no questions asked" use a component like Label, then I recommend using JLayer instead.
Unfourtantly, I've not had time to update my examples to use JLayer, but they use the predecessor library, JXLayer
Java rotating non-square JPanel component
Is there any way I can rotate this 90 degrees?

List of graphics2D

Howcome this code below wont work? I want to add new Ovals to the ArrayList every 200 ms and display them and run them one by one. It works fine when Im running one particle s.runner(); but it doesnt seem to run all my particles.
MAIN:
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.Timer;
public class ExempelGraphics extends JFrame implements ActionListener {
Timer t;
private int inc = 0;
ArrayList<Surface> particle = new ArrayList<>();
Surface s;
public ExempelGraphics() {
t = new Timer(10, this);
t.start();
s = new Surface(10, 10);
initUI();
}
private void initUI() {
add(s);
setSize(350, 250);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void actionPerformed(ActionEvent e) {
// s.runner();
// add
if (inc++ % 20 == 0) {
particle.add(new Surface(10, 10));
}
// display
for (int i = 0; i < particle.size(); i++) {
Surface p = particle.get(i);
p.runner();
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
ExempelGraphics ex = new ExempelGraphics();
ex.setVisible(true);
}
});
}
}
GRAPHICS:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JPanel;
public class Surface extends JPanel {
private int locX = 0;
private int locY = 0;
public Surface(int locX, int locY) {
this.locX = locX;
this.locY = locY;
}
public void runner() {
locX = locX + 1;
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.RED);
g2d.fillOval(locX, locY, 10, 10);
}
}

I think that you're program structure is broken. You should have only one JPanel here that does the drawing, that has its paintComponent overridden, and your Surface class should be a logical class and not a component class -- in other words, don't have it extend JPanel, and give it a public void draw(Graphics g) method where you draw the oval. Then have the drawing JPanel hold an ArrayList of these surfaces, and in the main JPanel's paintComponent method, iterate through the surfaces, calling each one's draw method.
Also your Timer's delay is not realistic and is too small. 15 would be much more realistic.
Also, don't call repaint() from within surface, since that will generate too many repaint calls unnecessarily. Instead call it from within the Timer's ActionListener after calling the runner methods on all the Surface objects.
Also note that every time you add a component to a JFrame's contentPane in a default fashion, you cover up the previously added components. If you go by my recommendations above, this isn't an issue since you'd only be adding that single JPanel to it.
For example:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
#SuppressWarnings("serial")
public class ExampleGraphics2 extends JPanel {
private static final int PREF_W = 650;
private static final int PREF_H = 500;
private static final int TIMER_DELAY = 20;
private List<Surface> surfaces = new ArrayList<>();
public ExampleGraphics2() {
new Timer(TIMER_DELAY, new TimerListener()).start();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
for (Surface surface : surfaces) {
surface.draw(g);
}
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private class TimerListener implements ActionListener {
private int index = 0;
#Override
public void actionPerformed(ActionEvent e) {
index++;
index %= 20;
if (index == 0) {
surfaces.add(new Surface(10, 10));
}
for (Surface surface : surfaces) {
surface.runner();
}
repaint();
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("Example Graphics 2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new ExampleGraphics2());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
package foo1;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
public class Surface {
private int locX = 0;
private int locY = 0;
public Surface(int locX, int locY) {
this.locX = locX;
this.locY = locY;
}
public void runner() {
locX = locX + 1;
}
public void draw(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.RED);
g2d.fillOval(locX, locY, 10, 10);
}
}

Change color of letter on mouse hover only

I have a Jframe with two buttons: 'A' and 'B'. Clicking the button 'A' should display the capital letter A in the JPanel. On mouse hover only, any 'A' letter within the canvas should be displayed in red. When the mouse leaves, the text color should be back to black.
I've coded for this and it works only once. The letter 'A' changes to red but does not change back to black. Also, it does not work for multiple 'A's
Code for JFrame:
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class DrawFrame extends JFrame{
private final int WIDTH = 500;
private final int HEIGHT = 300;
private GUIModel model;
private JButton number1;
private JButton number2;
private JPanel numberPanel;
private DrawPanel graphicsPanel;
public DrawFrame()
{
this.model = new GUIModel(" ");
createSelectionPanel();
createGraphicsPanel();
this.setSize(WIDTH, HEIGHT);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}
private void createSelectionPanel()
{
numberPanel = new JPanel();
ButtonListener listener = new ButtonListener();
number1 = new JButton("A");
number1.addActionListener(listener);
number2 = new JButton("B");
number2.addActionListener(listener);
numberPanel.setLayout(new GridLayout(2,2));
numberPanel.add(number1);
numberPanel.add(number2);
this.add(numberPanel, BorderLayout.WEST);
}
private void createGraphicsPanel()
{
//instantiate drawing panel
graphicsPanel = new DrawPanel(WIDTH, HEIGHT, model);
//add drawing panel to right
add(graphicsPanel);
}
private class ButtonListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent event) {
model.setDisplayString(event.getActionCommand());
}
}
//creates a drawing frame
public static void main(String[] args)
{
DrawFrame draw = new DrawFrame();
}
}
Code for JPanel:
import javax.swing.JPanel;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.ArrayList;
import java.util.List;
public class DrawPanel extends JPanel{
private static final long serialVersionUID = 3443814601865936618L;
private Font font = new Font("Default", Font.BOLD, 30);
private static final Color DEFAULT_TEXT_COLOR = Color.BLACK;
private static final Color HOVER_TEXT_COLOR = Color.RED;
private Color color = DEFAULT_TEXT_COLOR;
private List<GUIModel> numberList = new ArrayList<GUIModel>();
private GUIModel model;
boolean mouseHover = false;
public DrawPanel(int width, int height, GUIModel model){
this.setPreferredSize(new Dimension(width, height));
this.model = model;
//set white background for drawing panel
setBackground(Color.WHITE);
//add mouse listeners
MouseHandler mouseHandler = new MouseHandler();
this.addMouseListener(mouseHandler);
this.addMouseMotionListener(mouseHandler);
}
void checkForHover(MouseEvent event) {
FontMetrics metrics = getFontMetrics(font);
Graphics g = getGraphics();
Rectangle textBounds = metrics.getStringBounds("A", g).getBounds();
g.dispose();
int index = 0;
while (index < numberList.size()) {
Double x = numberList.get(index).getCoordinate().getX();
Double y = numberList.get(index).getCoordinate().getY();
textBounds.translate(x.intValue(), y.intValue());
if (textBounds.contains(event.getPoint())) {
color = HOVER_TEXT_COLOR;
}
else {
color = DEFAULT_TEXT_COLOR;
}
index++;
}
repaint(textBounds);
}
#Override
public void paintComponent(Graphics g){
super.paintComponent(g);
g.setFont(font);
g.setColor(color);
int index = 0;
while (index < numberList.size()) {
Double x = numberList.get(index).getCoordinate().getX();
Double y = numberList.get(index).getCoordinate().getY();
String display = numberList.get(index).getDisplayString();
g.drawString(display, x.intValue(), y.intValue());
index++;
}
if (model.getCoordinate() != null) {
Point p = model.getCoordinate();
g.drawString(model.getDisplayString(), p.x, p.y);
GUIModel number = new GUIModel();
number.setCoordinate(p);
number.setDisplayString(model.getDisplayString());
numberList.add(number);
}
}
//class to handle all mouse events
private class MouseHandler extends MouseAdapter implements MouseMotionListener
{
#Override
public void mousePressed(MouseEvent event)
{
model.setCoordinate(event.getPoint());
}
#Override
public void mouseReleased(MouseEvent event)
{
DrawPanel.this.repaint();
}
#Override
public void mouseEntered(MouseEvent event) {
checkForHover(event);
}
#Override
public void mouseMoved(MouseEvent event) {
checkForHover(event);
}
}
}
Code for GUIModel:
import java.awt.Point;
public class GUIModel {
private String displayString;
private Point coordinate;
public GUIModel() {}
public GUIModel(String displayString) {
this.displayString = displayString;
}
public void setDisplayString(String displayString) {
this.displayString = displayString;
}
public String getDisplayString() {
return displayString;
}
public Point getCoordinate() {
return coordinate;
}
public void setCoordinate(int x, int y) {
this.coordinate = new Point(x, y);
}
public void setCoordinate(Point coordinate) {
this.coordinate = coordinate;
}
}
Any help would be much appreciated. Thanks!

There's several misconceptions.
Graphics#drawString doesn't paint the text at the x/y position, so that the x/y is the top left corner of the String, but instead, the x/y position is the baseline of the font, this means that much of the text is draw above the y position, see Font Concepts for more details. This means that when you try and calculate the the Rectangle of the text, it's actually lower then where you painting it. Instead, you need to use y + ascent to get the text to position properly.
paintComponent can be called at any time for any number of reasons, many of which you don't control. To this end, paintComponent should only be used to paint the current state of the component and should never update or modify the state of the component. So adding a new GUIModel within the method is the wrong thing to do, instead, it should be added in the mouseClicked event of the MouseListener.
You're relying to much on the GUIModel variables. You should create a model only when you actually need it
Conceptually, this example address most of the issues mentioned above
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class DrawFrame extends JFrame {
private final int WIDTH = 500;
private final int HEIGHT = 300;
// private GUIModel model;
private JButton number1;
private JButton number2;
private JPanel numberPanel;
private DrawPanel graphicsPanel;
public DrawFrame() {
// this.model = new GUIModel(" ");
createSelectionPanel();
createGraphicsPanel();
this.setSize(WIDTH, HEIGHT);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}
private void createSelectionPanel() {
numberPanel = new JPanel();
ButtonListener listener = new ButtonListener();
number1 = new JButton("A");
number1.addActionListener(listener);
number2 = new JButton("B");
number2.addActionListener(listener);
numberPanel.setLayout(new GridLayout(2, 2));
numberPanel.add(number1);
numberPanel.add(number2);
this.add(numberPanel, BorderLayout.WEST);
}
private void createGraphicsPanel() {
//instantiate drawing panel
graphicsPanel = new DrawPanel(WIDTH, HEIGHT);
//add drawing panel to right
add(graphicsPanel);
}
private class ButtonListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent event) {
graphicsPanel.setDisplayString(event.getActionCommand());
}
}
//creates a drawing frame
public static void main(String[] args) {
DrawFrame draw = new DrawFrame();
}
public static class DrawPanel extends JPanel {
private static final long serialVersionUID = 3443814601865936618L;
private Font font = new Font("Default", Font.BOLD, 30);
private static final Color DEFAULT_TEXT_COLOR = Color.BLACK;
private static final Color HOVER_TEXT_COLOR = Color.RED;
private Color color = DEFAULT_TEXT_COLOR;
private List<GUIModel> numberList = new ArrayList<GUIModel>();
boolean mouseHover = false;
private String displayString;
private GUIModel hoverModel;
public DrawPanel(int width, int height) {
this.setPreferredSize(new Dimension(width, height));
//set white background for drawing panel
setBackground(Color.WHITE);
//add mouse listeners
MouseHandler mouseHandler = new MouseHandler();
this.addMouseListener(mouseHandler);
this.addMouseMotionListener(mouseHandler);
}
protected Rectangle getBounds(GUIModel model) {
FontMetrics metrics = getFontMetrics(font);
Double x = model.getCoordinate().getX();
Double y = model.getCoordinate().getY();
Rectangle textBounds = new Rectangle(
x.intValue(),
y.intValue(),
metrics.stringWidth(model.getDisplayString()),
metrics.getHeight());
return textBounds;
}
void checkForHover(MouseEvent event) {
Rectangle textBounds = null;
if (hoverModel != null) {
textBounds = getBounds(hoverModel);
}
hoverModel = null;
if (textBounds != null) {
repaint(textBounds);
}
for (GUIModel model : numberList) {
textBounds = getBounds(model);
if (textBounds.contains(event.getPoint())) {
hoverModel = model;
repaint(textBounds);
break;
}
}
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setFont(font);
g.setColor(DEFAULT_TEXT_COLOR);
FontMetrics fm = g.getFontMetrics();
for (GUIModel model : numberList) {
if (model != hoverModel) {
Double x = model.getCoordinate().getX();
Double y = model.getCoordinate().getY();
String display = model.getDisplayString();
g.drawString(display, x.intValue(), y.intValue() + fm.getAscent());
}
}
if (hoverModel != null) {
g.setColor(HOVER_TEXT_COLOR);
Double x = hoverModel.getCoordinate().getX();
Double y = hoverModel.getCoordinate().getY();
String display = hoverModel.getDisplayString();
g.drawString(display, x.intValue(), y.intValue() + fm.getAscent());
}
// if (model.getCoordinate() != null) {
// Point p = model.getCoordinate();
// g.drawString(model.getDisplayString(), p.x, p.y);
//// GUIModel number = new GUIModel();
//// number.setCoordinate(p);
//// number.setDisplayString(model.getDisplayString());
//// numberList.add(number);
// }
}
public void setDisplayString(String text) {
displayString = text;
}
//class to handle all mouse events
private class MouseHandler extends MouseAdapter implements MouseMotionListener {
#Override
public void mouseClicked(MouseEvent e) {
GUIModel model = new GUIModel(displayString);
model.setCoordinate(e.getPoint());
numberList.add(model);
repaint();
}
#Override
public void mouseMoved(MouseEvent event) {
checkForHover(event);
}
}
}
public static class GUIModel {
private String displayString;
private Point coordinate;
public GUIModel() {
}
public GUIModel(String displayString) {
this.displayString = displayString;
}
public void setDisplayString(String displayString) {
this.displayString = displayString;
}
public String getDisplayString() {
return displayString;
}
public Point getCoordinate() {
return coordinate;
}
public void setCoordinate(int x, int y) {
this.coordinate = new Point(x, y);
}
public void setCoordinate(Point coordinate) {
this.coordinate = coordinate;
}
}
}

Rotate Shape Doens't Work [duplicate]

I have an image I am rotating when the user clicks on a button. But it is not working.
I would like to see the image rotating gradually to 90 degrees till it stops but it doesn't. The image must rotate 90 degrees gradually when the button is clicked.
I have created an SSCCE to demonstrate the problem. Please replace the image in the CrossingPanelSSCE class with any image of your choice. Just put the image in your images folder and name it images/railCrossing.JPG.
RotateButtonSSCE
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Action;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JPanel;
public class RotateButtonSSCE extends JPanel implements ActionListener{
private JButton rotate = new JButton("Rotate");
private VisualizationPanelSSCE vis = new VisualizationPanelSSCE();
public RotateButtonSSCE() {
this.setBorder(BorderFactory.createTitledBorder("Rotate Button "));
this.rotate.addActionListener(this);
this.add(rotate);
}
public void actionPerformed(ActionEvent ev) {
vis.rotatetheCrossing();
}
}
CrossingPanelSSCE
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
import javax.swing.border.TitledBorder;
public class CrossingPanelSSCE extends JPanel{
private static final long serialVersionUID = 1L;
// private data members
private Image crossingImage;
private int currentRotationAngle;
private int imageWidth;
private int imageHeight;
private AffineTransform affineTransform;
private boolean clockwise;
private static int ROTATE_ANGLE_OFFSET = 2;
private int xCoordinate;
private int yCoordinate;
private static javax.swing.Timer timer;
private void initialize(){
this.crossingImage = Toolkit.getDefaultToolkit().getImage("images/railCrossing.JPG");
this.imageWidth = this.getCrossingImage().getWidth(this);
this.imageHeight = this.getCrossingImage().getHeight(this);
this.affineTransform = new AffineTransform();
currentRotationAngle = 90;
timer = new javax.swing.Timer(20, new MoveListener());
}
public CrossingPanelSSCE(int x, int y) {
this.setxCoordinate(x);
this.setyCoordinate(y);
this.setPreferredSize(new Dimension(50, 50));
this.setBackground(Color.red);
TitledBorder border = BorderFactory.createTitledBorder("image");
this.setLayout(new FlowLayout());
this.initialize();
}
public void paintComponent(Graphics grp){
Rectangle rect = this.getBounds();
Graphics2D g2d = (Graphics2D)grp;
g2d.setColor(Color.BLACK);
this.getAffineTransform().setToTranslation(this.getxCoordinate(), this.getyCoordinate());
//rotate with the rotation point as the mid of the image
this.getAffineTransform().rotate(Math.toRadians(this.getCurrentRotationAngle()), this.getCrossingImage().getWidth(this) /2,
this.getCrossingImage().getHeight(this)/2);
//draw the image using the AffineTransform
g2d.drawImage(this.getCrossingImage(), this.getAffineTransform(), this);
}
public void rotateCrossing(){
System.out.println("CurrentRotationAngle: " + currentRotationAngle);
this.currentRotationAngle += ROTATE_ANGLE_OFFSET;
//int test = currentRotationAngle % 90;
if(currentRotationAngle % 90 == 0){
setCurrentRotationAngle(currentRotationAngle);
timer.stop();
}
//repaint the image panel
repaint();
}
void start() {
if (timer != null) {
timer.start();
}
}
private class MoveListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
rotateCrossing();
}
}
public Image getCrossingImage() {
return crossingImage;
}
public void setCrossingImage(Image crossingImage) {
this.crossingImage = crossingImage;
}
public int getCurrentRotationAngle() {
return currentRotationAngle;
}
public void setCurrentRotationAngle(int currentRotationAngle) {
this.currentRotationAngle = currentRotationAngle;
}
public int getImageWidth() {
return imageWidth;
}
public void setImageWidth(int imageWidth) {
this.imageWidth = imageWidth;
}
public int getImageHeight() {
return imageHeight;
}
public void setImageHeight(int imageHeight) {
this.imageHeight = imageHeight;
}
public AffineTransform getAffineTransform() {
return affineTransform;
}
public void setAffineTransform(AffineTransform affineTransform) {
this.affineTransform = affineTransform;
}
public boolean isClockwise() {
return clockwise;
}
public void setClockwise(boolean clockwise) {
this.clockwise = clockwise;
}
public int getxCoordinate() {
return xCoordinate;
}
public void setxCoordinate(int xCoordinate) {
this.xCoordinate = xCoordinate;
}
public int getyCoordinate() {
return yCoordinate;
}
public void setyCoordinate(int yCoordinate) {
this.yCoordinate = yCoordinate;
}
public javax.swing.Timer getTimer() {
return timer;
}
public void setTimer(javax.swing.Timer timer) {
this.timer = timer;
}
}
VisualizationPanelSSCE
import gui.CrossingPanel;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.GeneralPath;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.border.TitledBorder;
import application.Robot2;
public class VisualizationPanelSSCE extends JPanel{
//private data members
private GeneralPath path;
private Shape horizontalRail;
private Shape verticalRail;
private static int LENGTH = 350;
private CrossingPanelSSCE crossingP;
private void initializeComponents(){
this.path = new GeneralPath();
this.horizontalRail = this.createHorizontalRail();
this.verticalRail = this.createVerticalRail();
this.crossingP = new CrossingPanelSSCE(328,334);
}
public VisualizationPanelSSCE(){
this.initializeComponents();
this.setPreferredSize(new Dimension(400,400));
TitledBorder border = BorderFactory.createTitledBorder("Rotation");
this.setBorder(border);
}
public GeneralPath getPath() {
return path;
}
public void setPath(GeneralPath path) {
this.path = path;
}
private Shape createHorizontalRail(){
this.getPath().moveTo(5, LENGTH);
this.getPath().lineTo(330, 350);
this.getPath().closePath();
return this.getPath();
}
private Shape createVerticalRail(){
this.getPath().moveTo(350, 330);
this.getPath().lineTo(350,10);
this.getPath().closePath();
return this.getPath();
}
public void paintComponent(Graphics comp){
super.paintComponent(comp);
Graphics2D comp2D = (Graphics2D)comp;
BasicStroke pen = new BasicStroke(15.0F, BasicStroke.CAP_BUTT,BasicStroke.JOIN_ROUND);
comp2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
comp2D.setPaint(Color.black);
comp2D.setBackground(Color.WHITE);
comp2D.draw(this.horizontalRail);
this.crossingP.paintComponent(comp2D);
}
public CrossingPanelSSCE getCrossingP() {
return crossingP;
}
public void setCrossingP(CrossingPanelSSCE crossingP) {
this.crossingP = crossingP;
}
public void rotatetheCrossing(){
Runnable rotateCrossing1 = new Runnable(){
public void run() {
crossingP.start();
}
};
SwingUtilities.invokeLater(rotateCrossing1);
}
}
TestGUISSCE it contains the main method.
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.Random;
import javax.swing.*;
public class TestGUISSCE{
private RotateButtonSSCE rotate = new RotateButtonSSCE();
private VisualizationPanelSSCE vision = new VisualizationPanelSSCE();
public void createGui(){
JFrame frame = new JFrame("Example");
frame.setSize(new Dimension(500, 500));
JPanel pane = new JPanel();
pane.add(this.vision);
pane.add(rotate);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(pane);
frame.setVisible(true);
}
public static void main(String[] args) {
new TestGUISSCE().createGui();
}
}

In addition to #tulskiy's helpful observations, I would add two points:
Always construct your GUI on the event dispatch thread, as shown below.
An sscce should be a Short, Self Contained, Correct (Compilable), Example. As a convenience, don't require others to recreate multiple public classes; use top-level (package-private) or nested classes. As this is a graphics problem, use a public or synthetic image that reflects your problem.
In the example below, paintComponent() alters the graphics context's transform to effect the rotation. Note that the operations are performed in the (apparent) reverse of the declaration order: First, the image's center is translated to the origin; second, the image is rotated; third, the image's center is translated to the center of the panel. You can see the effect by resizing the panel.
Addendum: See also this alternative approach using AffineTransform.
package overflow;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.swing.*;
/**
* #see https://stackoverflow.com/questions/3371227
* #see https://stackoverflow.com/questions/3405799
*/
public class RotateApp {
private static final int N = 3;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
frame.setLayout(new GridLayout(N, N, N, N));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
for (int i = 0; i < N * N; i++) {
frame.add(new RotatePanel());
}
frame.pack();
frame.setVisible(true);
}
});
}
}
class RotatePanel extends JPanel implements ActionListener {
private static final int SIZE = 256;
private static double DELTA_THETA = Math.PI / 90;
private final Timer timer = new Timer(25, this);
private Image image = RotatableImage.getImage(SIZE);
private double dt = DELTA_THETA;
private double theta;
public RotatePanel() {
this.setBackground(Color.lightGray);
this.setPreferredSize(new Dimension(
image.getWidth(null), image.getHeight(null)));
this.addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
image = RotatableImage.getImage(SIZE);
dt = -dt;
}
});
timer.start();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.translate(this.getWidth() / 2, this.getHeight() / 2);
g2d.rotate(theta);
g2d.translate(-image.getWidth(this) / 2, -image.getHeight(this) / 2);
g2d.drawImage(image, 0, 0, null);
}
#Override
public void actionPerformed(ActionEvent e) {
theta += dt;
repaint();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(SIZE, SIZE);
}
}
class RotatableImage {
private static final Random r = new Random();
static public Image getImage(int size) {
BufferedImage bi = new BufferedImage(
size, size, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = bi.createGraphics();
g2d.setRenderingHint(
RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setPaint(Color.getHSBColor(r.nextFloat(), 1, 1));
g2d.setStroke(new BasicStroke(size / 8));
g2d.drawLine(0, size / 2, size, size / 2);
g2d.drawLine(size / 2, 0, size / 2, size);
g2d.dispose();
return bi;
}
}

The code for Rotated Icon uses the AffineTransform to rotate about its center.

this.crossingP.paintComponent(comp2D);
Never do this! Your CrossingPane is not added to any component, so repaint() doesn't have any effect. You can check it by adding prints in the paintComponent() method. SO you need to add CrossingPane to the VisualizationPane:
setLayout(new BorderLayout());
add(crossingP, BorderLayout.CENTER);
There are some issues with centering the image, but this shouldn't be hard to fix.
PS. Read again about layouts and painting.