Develop Reference

How do I manipulate shapes within a zoomed panel in Java?

I have some code I found on the internet that allows me to control zooming and panning of a scrollable panel in Java but I want to be able to manipulate the shapes within this area and having trouble translating the x and y coordinates back to the original (unzoomed) dimensions ..
There are a few things I would like to do with these shapes but to start, how can I paint the two entity rectangles red when the mouse moves within them?
Here is code I have so far:
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.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
public class CanvasPane extends JPanel {
private static Canvas canvas;
public CanvasPane(boolean isDoubleBuffered) {
super(isDoubleBuffered);
setLayout(new BorderLayout());
canvas = new Canvas(1.0);
JScrollPane pane = new JScrollPane(canvas);
pane.getViewport().setBackground(Color.DARK_GRAY);
add(pane, BorderLayout.CENTER);
}
public static void main(String[] args) {
JFrame frame = new JFrame("Test Graphics");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new CanvasPane(true), BorderLayout.CENTER);
frame.pack();
frame.setSize(800, 600);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
//Initial scrolling of the canvas to its center
Rectangle canvasRectangle = canvas.getBounds();
Rectangle visibleRectangle = canvas.getVisibleRect();
double tx = (canvasRectangle.getWidth() - visibleRectangle.getWidth())/2;
double ty = (canvasRectangle.getHeight() - visibleRectangle.getHeight())/2;
visibleRectangle.setBounds((int)tx, (int)ty, visibleRectangle.width, visibleRectangle.height);
canvas.scrollRectToVisible(visibleRectangle);
}
}
class Canvas extends JComponent implements MouseWheelListener, MouseMotionListener, MouseListener {
private static final long serialVersionUID = 1L;
private double zoom = 1.0;
public static final double SCALE_STEP = 0.1d;
private Dimension initialSize;
private Point origin;
private double previousZoom = zoom;
private double scrollX = 0d;
private double scrollY = 0d;
private Rectangle2D workspace = new Rectangle2D.Double(0,0, 1024, 768);
private Rectangle entity1 = new Rectangle(10, 10, 100, 100);
private Rectangle entity2 = new Rectangle(300, 300, 100, 100);
public Canvas(double zoom) {
this.zoom = zoom;
addMouseWheelListener(this);
addMouseMotionListener(this);
addMouseListener(this);
setAutoscrolls(true);
setPreferredSize(new Dimension((int)workspace.getWidth(), (int)workspace.getHeight()));
}
#Override public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
//Zoom graphics
g2d.scale(zoom, zoom);
//translate graphics to be always in center of the canvas
Rectangle size = getBounds();
double tx = ((size.getWidth() - workspace.getWidth() * zoom) / 2) / zoom;
double ty = ((size.getHeight() - workspace.getHeight() * zoom) / 2) / zoom;
g2d.translate(tx, ty);
//Draw
g2d.setColor(Color.LIGHT_GRAY);
g2d.fill(workspace);
g2d.setColor(Color.DARK_GRAY);
g2d.setStroke(new BasicStroke(5.0f));
g2d.draw(workspace);
g2d.draw(entity1);
g2d.draw(entity2);
}
#Override public void setSize(Dimension size) {
super.setSize(size);
if (initialSize == null) {
this.initialSize = size;
}
}
#Override public void setPreferredSize(Dimension preferredSize) {
super.setPreferredSize(preferredSize);
if (initialSize == null) {
this.initialSize = preferredSize;
}
}
public void mouseWheelMoved(MouseWheelEvent e) {
double zoomFactor = -SCALE_STEP * e.getPreciseWheelRotation() * zoom;
zoom = Math.abs(zoom + zoomFactor);
//Here we calculate new size of canvas relative to zoom.
Dimension d = new Dimension(
(int)(initialSize.width * zoom),
(int)(initialSize.height * zoom));
setPreferredSize(d);
setSize(d);
validate();
followMouseOrCenter(e.getPoint());
previousZoom = zoom;
}
public void followMouseOrCenter(Point2D point) {
Rectangle size = getBounds();
Rectangle visibleRect = getVisibleRect();
scrollX = size.getCenterX();
scrollY = size.getCenterY();
if (point != null) {
scrollX = point.getX() / previousZoom * zoom - (point.getX() - visibleRect.getX());
scrollY = point.getY() / previousZoom * zoom - (point.getY() - visibleRect.getY());
}
visibleRect.setRect(scrollX, scrollY, visibleRect.getWidth(), visibleRect.getHeight());
scrollRectToVisible(visibleRect);
}
public void mouseDragged(MouseEvent e) {
if (origin != null) {
int deltaX = origin.x - e.getX();
int deltaY = origin.y - e.getY();
Rectangle view = getVisibleRect();
view.x += deltaX;
view.y += deltaY;
scrollRectToVisible(view);
}
}
public void mousePressed(MouseEvent e) {
origin = new Point(e.getPoint());
}
public void mouseMoved(MouseEvent e) {
}
public void mouseClicked(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
}
I have tried to calculate using following code but this isn't quite right
public void mouseMoved(MouseEvent e) {
double x = e.getX() / zoom;
double y = e.getY() / zoom;
double x2 = getWidth() - workspace.getWidth() * zoom;
double y2 = getHeight() - workspace.getHeight() * zoom;
if(x2 > 0) x -= x2;
if(y2 > 0) y -= y2;
Point p = new Point((int)x, (int)y);
if(entity1.contains(p)) {
intersects = true;
}
else {
intersects = false;
}
repaint();
}

This seems to work even better but I am not sure if its the cleanest solution ...
public void mouseMoved(MouseEvent e) {
double x = e.getX() / zoom;
double y = e.getY() / zoom;
// double x2 = getWidth() - workspace.getWidth() * zoom;
// double y2 = getHeight() - workspace.getHeight() * zoom;
double x2 = ((getWidth() - workspace.getWidth() * zoom) / 2) / zoom;
double y2 = ((getHeight() - workspace.getHeight() * zoom) / 2) / zoom;
if(x2 > 0) x -= x2;
if(y2 > 0) y -= y2;
Point p = new Point((int)x, (int)y);
if(entity1.contains(p)) {
intersects = true;
}
else {
intersects = false;
}
repaint();
}

How to animate Rectangle in JPanel?

I want to learn some tricks about JAVA for my project.
I want to animate my Rectangle leftoright and righttoleft but I can't apply the same functions for ball animation.
In addition,how can I start my ball in different x-direction with a border of y-coordinate ?
Thanks a lot for your advices and helping.
My codes:
import javax.swing.Timer;
import java.util.ArrayList;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class MultipleBall extends JApplet {
public MultipleBall() {
add(new BallControl());
}
class BallControl extends JPanel {
private BallPanel ballPanel = new BallPanel();
private JButton Suspend = new JButton("Suspend");
private JButton Resume = new JButton("Resume");
private JButton Add = new JButton("+1");
private JButton Subtract = new JButton("-1");
private JScrollBar Delay = new JScrollBar();
public BallControl() {
// Group buttons in a panel
JPanel panel = new JPanel();
panel.add(Suspend);
panel.add(Resume);
panel.add(Add);
panel.add(Subtract);
// Add ball and buttons to the panel
ballPanel.setBorder(new javax.swing.border.LineBorder(Color.red));
Delay.setOrientation(JScrollBar.HORIZONTAL);
ballPanel.setDelay(Delay.getMaximum());
setLayout(new BorderLayout());
add(Delay, BorderLayout.NORTH);
add(ballPanel, BorderLayout.CENTER);
add(panel, BorderLayout.SOUTH);
// Register listeners
Suspend.addActionListener(new Listener());
Resume.addActionListener(new Listener());
Add.addActionListener(new Listener());
Subtract.addActionListener(new Listener());
Delay.addAdjustmentListener(new AdjustmentListener() {
public void adjustmentValueChanged(AdjustmentEvent e) {
ballPanel.setDelay(Delay.getMaximum() - e.getValue());
}
});
}
class Listener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (e.getSource() == Suspend)
ballPanel.suspend();
else if (e.getSource() == Resume)
ballPanel.resume();
else if (e.getSource() == Add)
ballPanel.add();
else if (e.getSource() == Subtract)
ballPanel.subtract();
}
}
}
class BallPanel extends JPanel {
private int delay = 30;
private ArrayList<Ball> list = new ArrayList<Ball>();
// Create a timer with the initial delay
protected Timer timer = new Timer(delay, new ActionListener() {
/** Handle the action event */
public void actionPerformed(ActionEvent e) {
repaint();
}
});
public BallPanel() {
timer.start();
}
public void add() {
list.add(new Ball());
}
public void subtract() {
if (list.size() > 0)
list.remove(list.size() - 1); // Remove the last ball
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawRect(185, 279, 50, 15);
g.setColor(Color.RED);
g.fillRect(185, 279, 50, 15);
for (int i = 0; i < list.size(); i++) {
Ball ball = (Ball) list.get(i); // Get a ball
g.setColor(ball.color); // Set ball color
// Check boundaries
if (ball.x < 0 || ball.x > getWidth())
ball.dx = -ball.dx;
if (ball.y < 0 || ball.y > getHeight())
ball.dy = -ball.dy;
// Adjust ball position
ball.x += ball.dx;
// ball.y += ball.dy;
g.fillOval(ball.x - ball.radius, ball.y - ball.radius,
ball.radius * 2, ball.radius * 2);
}
}
public void suspend() {
timer.stop();
}
public void resume() {
timer.start();
}
public void setDelay(int delay) {
this.delay = delay;
timer.setDelay(delay);
}
}
class Ball {
int x = 20;
int y = 20; // Current ball position
int dx = 2; // Increment on ball's x-coordinate
int dy = 2; // Increment on ball's y-coordinate
int radius = 15; // Ball radius
Color color = new Color((int) (Math.random() * 256),
(int) (Math.random() * 256), (int) (Math.random() * 256));
}
/** Main method */
public static void main(String[] args) {
JFrame frame = new JFrame();
JApplet applet = new MultipleBallApp();
frame.add(applet);
frame.setTitle("MultipleBallApp");
frame.setLocationRelativeTo(null); // Center the frame
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
frame.setLocationRelativeTo(null); // Center the frame
frame.setVisible(true);
}
}

can't apply the same functions for ball animation
This is probably your first mistake. In fact, this is exactly what you should be trying to do. The idea is, you should be trying to devise a means by what is painted/animated is abstract so it doesn't matter what the shape is you want to paint, you can apply it to the sam basic animation process...
For example, you could start with some kind interface which describes the basic properties of an animated entity...
public interface AnimatedShape {
public void update(Rectangle bounds);
public void paint(JComponent parent, Graphics2D g2d);
}
This says that an animated entity can be updated (moved) and painted. By convention (and because I'm lazy), I like to create an abstract implementation which implements the most common aspects...
public abstract class AbstractAnimatedShape implements AnimatedShape {
private Rectangle bounds;
private int dx, dy;
public AbstractAnimatedShape() {
}
public void setBounds(Rectangle bounds) {
this.bounds = bounds;
}
public Rectangle getBounds() {
return bounds;
}
public int getDx() {
return dx;
}
public int getDy() {
return dy;
}
public void setDx(int dx) {
this.dx = dx;
}
public void setDy(int dy) {
this.dy = dy;
}
#Override
public void update(Rectangle parentBounds) {
Rectangle bounds = getBounds();
int dx = getDx();
int dy = getDy();
bounds.x += dx;
bounds.y += dy;
if (bounds.x < parentBounds.x) {
bounds.x = parentBounds.x;
setDx(dx *= -1);
} else if (bounds.x + bounds.width > parentBounds.x + parentBounds.width) {
bounds.x = parentBounds.x + (parentBounds.width - bounds.width);
setDx(dx *= -1);
}
if (bounds.y < parentBounds.y) {
bounds.y = parentBounds.y;
setDy(dy *= -1);
} else if (bounds.y + bounds.height > parentBounds.y + parentBounds.height) {
bounds.y = parentBounds.y + (parentBounds.height - bounds.height);
setDy(dy *= -1);
}
}
}
And then start creating implementations...
public class AnimatedBall extends AbstractAnimatedShape {
private Color color;
public AnimatedBall(int x, int y, int radius, Color color) {
setBounds(new Rectangle(x, y, radius * 2, radius * 2));
this.color = color;
setDx(Math.random() > 0.5 ? 2 : -2);
setDy(Math.random() > 0.5 ? 2 : -2);
}
public Color getColor() {
return color;
}
#Override
public void paint(JComponent parent, Graphics2D g2d) {
Rectangle bounds = getBounds();
g2d.setColor(getColor());
g2d.fillOval(bounds.x, bounds.y, bounds.width, bounds.height);
}
}
In this manner, you can customise the way that the entity is animated and painted, but the basic logic for each instance of the entity is the same...
But what's all the point of this...
Basically, what it allows us to do is produce a "virtual" concept of all the animated objects and simplify there management, for example...
Instead of using a "tightly" coupled List, we can use a loosely couple List instead...
private ArrayList<AnimatedShape> list = new ArrayList<AnimatedShape>();
Then when we want the entities to be updated, we simply need to iterate the List and ask the entities to update...
protected Timer timer = new Timer(delay, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
for (AnimatedShape ball : list) {
ball.update(getBounds());
}
repaint();
}
});
And when they need to be painted...
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
for (AnimatedShape ball : list) {
ball.paint(this, g2d);
}
}
Because the BallPane doesn't care what actually type of entity it is, but only that it's a type of AnimatedShape...makes life easier...
Now, my implementation of the AnimatedBall already randomise the direction of each instance of the ball, but you can also randomise the starting position when the ball is added using something like...
public void add() {
int radius = 15;
// Randomised position
int x = (int)(Math.random() * (getWidth() - (radius * 2))) + radius;
int y = (int)(Math.random() * (getHeight() - (radius * 2))) + radius;
Color color = new Color((int) (Math.random() * 256),
(int) (Math.random() * 256), (int) (Math.random() * 256));
AnimatedBall ball = new AnimatedBall(x, y, radius, color);
list.add(ball);
}
But how does this help you with adding a rectangle?
You now need to create an AnimatedRectangle that extends from AbstractAnimatedShape and implemented the required methods and add instances of this to the List of AnimatedShapes in the BallPane.
If you don't want the rectangle to be managed within the same list, you could create another list and manage it sepearatly (it create two additional methods, update(List<AnimatedShape>) and paint(List<AnimatedShape>, Graphics2D) passing in each individual list so as to reduce the duplicate code, but that's me)...
You can restrict the rectangles vertical movement by overriding the setDy method and ignoring any changes, for example
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollBar;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class MultipleBall {
public MultipleBall() {
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("MultipleBallApp");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new BallControl());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class BallControl extends JPanel {
private BallPanel ballPanel = new BallPanel();
private JButton Suspend = new JButton("Suspend");
private JButton Resume = new JButton("Resume");
private JButton Add = new JButton("+1");
private JButton Subtract = new JButton("-1");
private JScrollBar Delay = new JScrollBar();
public BallControl() {
// Group buttons in a panel
JPanel panel = new JPanel();
panel.add(Suspend);
panel.add(Resume);
panel.add(Add);
panel.add(Subtract);
// Add ball and buttons to the panel
ballPanel.setBorder(new javax.swing.border.LineBorder(Color.red));
Delay.setOrientation(JScrollBar.HORIZONTAL);
ballPanel.setDelay(Delay.getMaximum());
setLayout(new BorderLayout());
add(Delay, BorderLayout.NORTH);
add(ballPanel, BorderLayout.CENTER);
add(panel, BorderLayout.SOUTH);
// Register listeners
Suspend.addActionListener(new Listener());
Resume.addActionListener(new Listener());
Add.addActionListener(new Listener());
Subtract.addActionListener(new Listener());
Delay.addAdjustmentListener(new AdjustmentListener() {
public void adjustmentValueChanged(AdjustmentEvent e) {
ballPanel.setDelay(Delay.getMaximum() - e.getValue());
}
});
}
class Listener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (e.getSource() == Suspend) {
ballPanel.suspend();
} else if (e.getSource() == Resume) {
ballPanel.resume();
} else if (e.getSource() == Add) {
ballPanel.add();
} else if (e.getSource() == Subtract) {
ballPanel.subtract();
}
}
}
}
class BallPanel extends JPanel {
private int delay = 30;
private ArrayList<AnimatedShape> list = new ArrayList<AnimatedShape>();
private AnimatedRectange rectangle;
public BallPanel() {
this.rectangle = new AnimatedRectange(-25, 200, 50, 25, Color.RED);
timer.start();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
// Create a timer with the initial delay
protected Timer timer = new Timer(delay, new ActionListener() {
/**
* Handle the action event
*/
#Override
public void actionPerformed(ActionEvent e) {
for (AnimatedShape ball : list) {
ball.update(getBounds());
}
rectangle.update(getBounds());
repaint();
}
});
public void add() {
int radius = 15;
// Randomised position
int x = (int) (Math.random() * (getWidth() - (radius * 2))) + radius;
int y = (int) (Math.random() * (getHeight() - (radius * 2))) + radius;
Color color = new Color((int) (Math.random() * 256),
(int) (Math.random() * 256), (int) (Math.random() * 256));
AnimatedBall ball = new AnimatedBall(x, y, radius, color);
list.add(ball);
}
public void subtract() {
if (list.size() > 0) {
list.remove(list.size() - 1); // Remove the last ball
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
for (AnimatedShape ball : list) {
ball.paint(this, g2d);
}
rectangle.paint(this, g2d);
}
public void suspend() {
timer.stop();
}
public void resume() {
timer.start();
}
public void setDelay(int delay) {
this.delay = delay;
timer.setDelay(delay);
}
}
public interface AnimatedShape {
public void update(Rectangle bounds);
public void paint(JComponent parent, Graphics2D g2d);
}
public abstract class AbstractAnimatedShape implements AnimatedShape {
private Rectangle bounds;
private int dx, dy;
public AbstractAnimatedShape() {
}
public void setBounds(Rectangle bounds) {
this.bounds = bounds;
}
public Rectangle getBounds() {
return bounds;
}
public int getDx() {
return dx;
}
public int getDy() {
return dy;
}
public void setDx(int dx) {
this.dx = dx;
}
public void setDy(int dy) {
this.dy = dy;
}
#Override
public void update(Rectangle parentBounds) {
Rectangle bounds = getBounds();
int dx = getDx();
int dy = getDy();
bounds.x += dx;
bounds.y += dy;
if (bounds.x < parentBounds.x) {
bounds.x = parentBounds.x;
setDx(dx *= -1);
} else if (bounds.x + bounds.width > parentBounds.x + parentBounds.width) {
bounds.x = parentBounds.x + (parentBounds.width - bounds.width);
setDx(dx *= -1);
}
if (bounds.y < parentBounds.y) {
bounds.y = parentBounds.y;
setDy(dy *= -1);
} else if (bounds.y + bounds.height > parentBounds.y + parentBounds.height) {
bounds.y = parentBounds.y + (parentBounds.height - bounds.height);
setDy(dy *= -1);
}
}
}
public class AnimatedBall extends AbstractAnimatedShape {
private Color color;
public AnimatedBall(int x, int y, int radius, Color color) {
setBounds(new Rectangle(x, y, radius * 2, radius * 2));
this.color = color;
setDx(Math.random() > 0.5 ? 2 : -2);
setDy(Math.random() > 0.5 ? 2 : -2);
}
public Color getColor() {
return color;
}
#Override
public void paint(JComponent parent, Graphics2D g2d) {
Rectangle bounds = getBounds();
g2d.setColor(getColor());
g2d.fillOval(bounds.x, bounds.y, bounds.width, bounds.height);
}
}
public class AnimatedRectange extends AbstractAnimatedShape {
private Color color;
public AnimatedRectange(int x, int y, int width, int height, Color color) {
setBounds(new Rectangle(x, y, width, height));
this.color = color;
setDx(2);
}
// Don't want to adjust the vertical speed
#Override
public void setDy(int dy) {
}
#Override
public void paint(JComponent parent, Graphics2D g2d) {
Rectangle bounds = getBounds();
g2d.setColor(color);
g2d.fill(bounds);
}
}
/**
* Main method
*/
public static void main(String[] args) {
new MultipleBall();
}
}
Amendment
You really should avoid adding JApplet to a JFrame, an applet has a prescribed life cycle and management process which you are ignoring. Better to focus on just using the BallControl panel as the core UI element and then add this to what ever top level container you want
You may find a JSlider more piratical then a JScrollBar, not to mention, it will look better on different platforms, most uses understand what a slider is used for...

Add a static variable like ballCount and add 1 to it every time you make a ball. In the Ball class, change the definition of y to something likey = 20 + ballcount*(radius*2+distanceInBalls)
public class RandomTests extends JApplet {
public RandomTests() {
add(new BallControl());
}
static int ballCount = 0;
class BallControl extends JPanel {
private BallPanel ballPanel = new BallPanel();
private JButton Suspend = new JButton("Suspend");
private JButton Resume = new JButton("Resume");
private JButton Add = new JButton("+1");
private JButton Subtract = new JButton("-1");
private JScrollBar Delay = new JScrollBar();
public BallControl() {
// Group buttons in a panel
JPanel panel = new JPanel();
panel.add(Suspend);
panel.add(Resume);
panel.add(Add);
panel.add(Subtract);
// Add ball and buttons to the panel
ballPanel.setBorder(new javax.swing.border.LineBorder(Color.red));
Delay.setOrientation(JScrollBar.HORIZONTAL);
ballPanel.setDelay(Delay.getMaximum());
setLayout(new BorderLayout());
add(Delay, BorderLayout.NORTH);
add(ballPanel, BorderLayout.CENTER);
add(panel, BorderLayout.SOUTH);
// Register listeners
Suspend.addActionListener(new Listener());
Resume.addActionListener(new Listener());
Add.addActionListener(new Listener());
Subtract.addActionListener(new Listener());
Delay.addAdjustmentListener(new AdjustmentListener() {
public void adjustmentValueChanged(AdjustmentEvent e) {
ballPanel.setDelay(Delay.getMaximum() - e.getValue());
}
});
}
class Listener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (e.getSource() == Suspend) ballPanel.suspend();
else if (e.getSource() == Resume) ballPanel.resume();
else if (e.getSource() == Add) ballPanel.add();
else if (e.getSource() == Subtract) ballPanel.subtract();
}
}
}
class BallPanel extends JPanel {
private int delay = 30;
private ArrayList<Ball> list = new ArrayList<Ball>();
// Create a timer with the initial delay
protected Timer timer = new Timer(delay, new ActionListener() {
/** Handle the action event */
public void actionPerformed(ActionEvent e) {
repaint();
}
});
public BallPanel() {
timer.start();
}
public void add() {
list.add(new Ball());
ballCount++;
}
public void subtract() {
if (list.size() > 0) list.remove(list.size() - 1); // Remove the last ball
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawRect(185, 279, 50, 15);
g.setColor(Color.RED);
g.fillRect(185, 279, 50, 15);
for (int i = 0; i < list.size(); i++) {
Ball ball = (Ball) list.get(i); // Get a ball
g.setColor(ball.color); // Set ball color
// Check boundaries
if (ball.x < 0 || ball.x > getWidth()) ball.dx = -ball.dx;
if (ball.y < 0 || ball.y > getHeight()) ball.dy = -ball.dy;
// Adjust ball position
ball.x += ball.dx;
// ball.y += ball.dy;
g.fillOval(ball.x - ball.radius, ball.y - ball.radius, ball.radius * 2, ball.radius * 2);
}
}
public void suspend() {
timer.stop();
}
public void resume() {
timer.start();
}
public void setDelay(int delay) {
this.delay = delay;
timer.setDelay(delay);
}
}
class Ball {
int radius = 15; // Ball radius
int x = radius;
int y = 20 + (radius * ballCount * 2 + 15); // Current ball position
int dx = 2; // Increment on ball's x-coordinate
int dy = 2; // Increment on ball's y-coordinate
Color color = new Color((int) (Math.random() * 256), (int) (Math.random() * 256), (int) (Math.random() * 256));
}
public static void main(String[] args) {
JFrame frame = new JFrame();
JApplet applet = new RandomTests();
frame.add(applet);
frame.setTitle("MultipleBallApp");
frame.setLocationRelativeTo(null); // Center the frame
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
frame.setLocationRelativeTo(null); // Center the frame
frame.setVisible(true);
}
}

How to make an image move while listening to a keypress in Java.

I'm starting to learn java programming and I think it's cool to learn java through game development. I know how to draw image and listen to a keypress then move that image. But is it possible to make the image move back and forth to the window while the window is listening to a keypress? Like for example, while the image or object(like spaceship) is moving left to right in the window, then if I press space key, a laser will fire at the bottom of the screen( cool huh :D ). But basically I just want to know how to make the image move left to right while the window is listening to a keypress.
I'm thinking that I will add a key listener to my window then fire an infinite loop to move the image. Or do I need to learn about threading so that another thread will move the object?
Please advise.
Many thanks.

Yep, a Swing Timer and Key Bindings would work well. Here's another example (mine) :)
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class AnimationWithKeyBinding {
private static void createAndShowUI() {
AnimationPanel panel = new AnimationPanel(); // the drawing JPanel
JFrame frame = new JFrame("Animation With Key Binding");
frame.getContentPane().add(panel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}
#SuppressWarnings("serial")
class AnimationPanel extends JPanel {
public static final int SPRITE_WIDTH = 20;
public static final int PANEL_WIDTH = 400;
public static final int PANEL_HEIGHT = 400;
private static final int MAX_MSTATE = 25;
private static final int SPIN_TIMER_PERIOD = 16;
private static final int SPRITE_STEP = 3;
private int mState = 0;
private int mX = (PANEL_WIDTH - SPRITE_WIDTH) / 2;
private int mY = (PANEL_HEIGHT - SPRITE_WIDTH) / 2;
private int oldMX = mX;
private int oldMY = mY;
private boolean moved = false;
// an array of sprite images that are drawn sequentially
private BufferedImage[] spriteImages = new BufferedImage[MAX_MSTATE];
public AnimationPanel() {
// create and start the main animation timer
new Timer(SPIN_TIMER_PERIOD, new SpinTimerListener()).start();
setPreferredSize(new Dimension(PANEL_WIDTH, PANEL_HEIGHT));
setBackground(Color.white);
createSprites(); // create the images
setupKeyBinding();
}
private void setupKeyBinding() {
int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
InputMap inMap = getInputMap(condition);
ActionMap actMap = getActionMap();
// this uses an enum of Direction that holds ints for the arrow keys
for (Direction direction : Direction.values()) {
int key = direction.getKey();
String name = direction.name();
// add the key bindings for arrow key and shift-arrow key
inMap.put(KeyStroke.getKeyStroke(key, 0), name);
inMap.put(KeyStroke.getKeyStroke(key, InputEvent.SHIFT_DOWN_MASK), name);
actMap.put(name, new MyKeyAction(this, direction));
}
}
// create a bunch of buffered images and place into an array,
// to be displayed sequentially
private void createSprites() {
for (int i = 0; i < spriteImages.length; i++) {
spriteImages[i] = new BufferedImage(SPRITE_WIDTH, SPRITE_WIDTH,
BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = spriteImages[i].createGraphics();
g2.setColor(Color.red);
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
double theta = i * Math.PI / (2 * spriteImages.length);
double x = SPRITE_WIDTH * Math.abs(Math.cos(theta)) / 2.0;
double y = SPRITE_WIDTH * Math.abs(Math.sin(theta)) / 2.0;
int x1 = (int) ((SPRITE_WIDTH / 2.0) - x);
int y1 = (int) ((SPRITE_WIDTH / 2.0) - y);
int x2 = (int) ((SPRITE_WIDTH / 2.0) + x);
int y2 = (int) ((SPRITE_WIDTH / 2.0) + y);
g2.drawLine(x1, y1, x2, y2);
g2.drawLine(y1, x2, y2, x1);
g2.dispose();
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(spriteImages[mState], mX, mY, null);
}
public void incrementX(boolean right) {
oldMX = mX;
if (right) {
mX = Math.min(getWidth() - SPRITE_WIDTH, mX + SPRITE_STEP);
} else {
mX = Math.max(0, mX - SPRITE_STEP);
}
moved = true;
}
public void incrementY(boolean down) {
oldMY = mY;
if (down) {
mY = Math.min(getHeight() - SPRITE_WIDTH, mY + SPRITE_STEP);
} else {
mY = Math.max(0, mY - SPRITE_STEP);
}
moved = true;
}
public void tick() {
mState = (mState + 1) % MAX_MSTATE;
}
private class SpinTimerListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
tick();
int delta = 20;
int width = SPRITE_WIDTH + 2 * delta;
int height = width;
// make sure to erase the old image
if (moved) {
int x = oldMX - delta;
int y = oldMY - delta;
repaint(x, y, width, height);
}
int x = mX - delta;
int y = mY - delta;
// draw the new image
repaint(x, y, width, height);
moved = false;
}
}
}
enum Direction {
UP(KeyEvent.VK_UP), DOWN(KeyEvent.VK_DOWN), LEFT(KeyEvent.VK_LEFT), RIGHT(KeyEvent.VK_RIGHT);
private int key;
private Direction(int key) {
this.key = key;
}
public int getKey() {
return key;
}
}
// Actions for the key binding
#SuppressWarnings("serial")
class MyKeyAction extends AbstractAction {
private AnimationPanel draw;
private Direction direction;
public MyKeyAction(AnimationPanel draw, Direction direction) {
this.draw = draw;
this.direction = direction;
}
#Override
public void actionPerformed(ActionEvent e) {
switch (direction) {
case UP:
draw.incrementY(false);
break;
case DOWN:
draw.incrementY(true);
break;
case LEFT:
draw.incrementX(false);
break;
case RIGHT:
draw.incrementX(true);
break;
default:
break;
}
}
}
Here is another example that uses this sprite sheet:
obtained from this site.
Again it's an example of drawing within a JPanel's paintComponent method and using Key Bindings to tell which direction to move.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.EnumMap;
import java.util.List;
import java.util.Map;
import javax.imageio.ImageIO;
import javax.swing.*;
#SuppressWarnings("serial")
public class Mcve3 extends JPanel {
private static final int PREF_W = 800;
private static final int PREF_H = 640;
private static final int TIMER_DELAY = 50;
private int spriteX = 400;
private int spriteY = 320;
private SpriteDirection spriteDirection = SpriteDirection.RIGHT;
private MySprite sprite = null;
private Timer timer = null;
public Mcve3() {
try {
sprite = new MySprite(spriteDirection, spriteX, spriteY);
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
setBackground(Color.WHITE);
setKeyBindings(SpriteDirection.LEFT, KeyEvent.VK_LEFT);
setKeyBindings(SpriteDirection.RIGHT, KeyEvent.VK_RIGHT);
setKeyBindings(SpriteDirection.FORWARD, KeyEvent.VK_DOWN);
setKeyBindings(SpriteDirection.AWAY, KeyEvent.VK_UP);
timer = new Timer(TIMER_DELAY, new TimerListener());
timer.start();
}
private void setKeyBindings(SpriteDirection dir, int keyCode) {
int condition = WHEN_IN_FOCUSED_WINDOW;
InputMap inputMap = getInputMap(condition);
ActionMap actionMap = getActionMap();
KeyStroke keyPressed = KeyStroke.getKeyStroke(keyCode, 0, false);
KeyStroke keyReleased = KeyStroke.getKeyStroke(keyCode, 0, true);
inputMap.put(keyPressed, keyPressed.toString());
inputMap.put(keyReleased, keyReleased.toString());
actionMap.put(keyPressed.toString(), new MoveAction(dir, false));
actionMap.put(keyReleased.toString(), new MoveAction(dir, true));
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
sprite.draw(g);
}
private class MoveAction extends AbstractAction {
private SpriteDirection dir;
private boolean released;
public MoveAction(SpriteDirection dir, boolean released) {
this.dir = dir;
this.released = released;
}
#Override
public void actionPerformed(ActionEvent e) {
if (released) {
sprite.setMoving(false);
} else {
sprite.setMoving(true);
sprite.setDirection(dir);
}
}
}
private class TimerListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
if (sprite.isMoving()) {
sprite.tick();
}
repaint();
}
}
private static void createAndShowGui() {
Mcve3 mainPanel = new Mcve3();
JFrame frame = new JFrame("MCVE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
class MySprite {
private static final String SPRITE_SHEET_PATH = "http://"
+ "orig12.deviantart.net/7db3/f/2010/338/3/3/"
+ "animated_sprite_sheet_32x32_by_digibody-d3479l2.gif";
private static final int MAX_MOVING_INDEX = 4;
private static final int DELTA = 4;
private SpriteDirection direction;
private Map<SpriteDirection, Image> standingImgMap = new EnumMap<>(SpriteDirection.class);
private Map<SpriteDirection, List<Image>> movingImgMap = new EnumMap<>(SpriteDirection.class);
private int x;
private int y;
private boolean moving = false;
private int movingIndex = 0;
public MySprite(SpriteDirection direction, int x, int y) throws IOException {
this.direction = direction;
this.x = x;
this.y = y;
createSprites();
}
public void draw(Graphics g) {
Image img = null;
if (!moving) {
img = standingImgMap.get(direction);
} else {
img = movingImgMap.get(direction).get(movingIndex);
}
g.drawImage(img, x, y, null);
}
private void createSprites() throws IOException {
URL spriteSheetUrl = new URL(SPRITE_SHEET_PATH);
BufferedImage img = ImageIO.read(spriteSheetUrl);
// get sub-images (sprites) from the sprite sheet
// magic numbers for getting sprites from sheet, all obtained by trial and error
int x0 = 0;
int y0 = 64;
int rW = 32;
int rH = 32;
for (int row = 0; row < 4; row++) {
SpriteDirection dir = SpriteDirection.values()[row];
List<Image> imgList = new ArrayList<>();
movingImgMap.put(dir, imgList);
int rY = y0 + row * rH;
for (int col = 0; col < 5; col++) {
int rX = x0 + col * rW;
BufferedImage subImg = img.getSubimage(rX, rY, rW, rH);
if (col == 0) {
// first image is standing
standingImgMap.put(dir, subImg);
} else {
// all others are moving
imgList.add(subImg);
}
}
}
}
public SpriteDirection getDirection() {
return direction;
}
public void setDirection(SpriteDirection direction) {
if (this.direction != direction) {
setMoving(false);
}
this.direction = direction;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
public boolean isMoving() {
return moving;
}
public void setMoving(boolean moving) {
this.moving = moving;
if (!moving) {
movingIndex = 0;
}
}
public void tick() {
if (moving) {
switch (direction) {
case RIGHT:
x += DELTA;
break;
case LEFT:
x -= DELTA;
break;
case FORWARD:
y += DELTA;
break;
case AWAY:
y -= DELTA;
}
movingIndex++;
movingIndex %= MAX_MOVING_INDEX;
}
}
public int getMovingIndex() {
return movingIndex;
}
public void setMovingIndex(int movingIndex) {
this.movingIndex = movingIndex;
}
}
enum SpriteDirection {
FORWARD, LEFT, AWAY, RIGHT
}

As an alternative to KeyListener, consider using actions and key bindings, discussed here. Derived from this example, the program below moves a line left, down, up or right using either buttons or keys.
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
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.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
/**
* #see https://stackoverflow.com/questions/6991648
* #see https://stackoverflow.com/questions/6887296
* #see https://stackoverflow.com/questions/5797965
*/
public class LinePanel extends JPanel {
private MouseHandler mouseHandler = new MouseHandler();
private Point p1 = new Point(100, 100);
private Point p2 = new Point(540, 380);
private boolean drawing;
public LinePanel() {
this.setPreferredSize(new Dimension(640, 480));
this.addMouseListener(mouseHandler);
this.addMouseMotionListener(mouseHandler);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.blue);
g2d.setRenderingHint(
RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setStroke(new BasicStroke(8,
BasicStroke.CAP_ROUND, BasicStroke.JOIN_BEVEL));
g.drawLine(p1.x, p1.y, p2.x, p2.y);
}
private class MouseHandler extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
drawing = true;
p1 = e.getPoint();
p2 = p1;
repaint();
}
#Override
public void mouseReleased(MouseEvent e) {
drawing = false;
p2 = e.getPoint();
repaint();
}
#Override
public void mouseDragged(MouseEvent e) {
if (drawing) {
p2 = e.getPoint();
repaint();
}
}
}
private class ControlPanel extends JPanel {
private static final int DELTA = 10;
public ControlPanel() {
this.add(new MoveButton("\u2190", KeyEvent.VK_LEFT, -DELTA, 0));
this.add(new MoveButton("\u2191", KeyEvent.VK_UP, 0, -DELTA));
this.add(new MoveButton("\u2192", KeyEvent.VK_RIGHT, DELTA, 0));
this.add(new MoveButton("\u2193", KeyEvent.VK_DOWN, 0, DELTA));
}
private class MoveButton extends JButton {
KeyStroke k;
int dx, dy;
public MoveButton(String name, int code, final int dx, final int dy) {
super(name);
this.k = KeyStroke.getKeyStroke(code, 0);
this.dx = dx;
this.dy = dy;
this.setAction(new AbstractAction(this.getText()) {
#Override
public void actionPerformed(ActionEvent e) {
LinePanel.this.p1.translate(dx, dy);
LinePanel.this.p2.translate(dx, dy);
LinePanel.this.repaint();
}
});
ControlPanel.this.getInputMap(
WHEN_IN_FOCUSED_WINDOW).put(k, k.toString());
ControlPanel.this.getActionMap().put(k.toString(), new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
MoveButton.this.doClick();
}
});
}
}
}
private void display() {
JFrame f = new JFrame("LinePanel");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(this);
f.add(new ControlPanel(), BorderLayout.SOUTH);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new LinePanel().display();
}
});
}
}

But basically I just want to know how to make the image move left to right while the window is listening to a keypress
You can use a Swing Timer to animate an image:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class TimerAnimation extends JLabel implements ActionListener
{
int deltaX = 2;
int deltaY = 3;
int directionX = 1;
int directionY = 1;
public TimerAnimation(
int startX, int startY,
int deltaX, int deltaY,
int directionX, int directionY,
int delay)
{
this.deltaX = deltaX;
this.deltaY = deltaY;
this.directionX = directionX;
this.directionY = directionY;
setIcon( new ImageIcon("dukewavered.gif") );
// setIcon( new ImageIcon("copy16.gif") );
setSize( getPreferredSize() );
setLocation(startX, startY);
new javax.swing.Timer(delay, this).start();
}
public void actionPerformed(ActionEvent e)
{
Container parent = getParent();
// Determine next X position
int nextX = getLocation().x + (deltaX * directionX);
if (nextX < 0)
{
nextX = 0;
directionX *= -1;
}
if ( nextX + getSize().width > parent.getSize().width)
{
nextX = parent.getSize().width - getSize().width;
directionX *= -1;
}
// Determine next Y position
int nextY = getLocation().y + (deltaY * directionY);
if (nextY < 0)
{
nextY = 0;
directionY *= -1;
}
if ( nextY + getSize().height > parent.getSize().height)
{
nextY = parent.getSize().height - getSize().height;
directionY *= -1;
}
// Move the label
setLocation(nextX, nextY);
}
public static void main(String[] args)
{
JPanel panel = new JPanel();
JFrame frame = new JFrame();
frame.setContentPane(panel);
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.getContentPane().setLayout(null);
// frame.getContentPane().add( new TimerAnimation(10, 10, 2, 3, 1, 1, 10) );
frame.getContentPane().add( new TimerAnimation(300, 100, 3, 2, -1, 1, 20) );
// frame.getContentPane().add( new TimerAnimation(0, 000, 5, 0, 1, 1, 20) );
frame.getContentPane().add( new TimerAnimation(0, 200, 5, 0, 1, 1, 80) );
frame.setSize(400, 400);
frame.setLocationRelativeTo( null );
frame.setVisible(true);
// frame.getContentPane().add( new TimerAnimation(10, 10, 2, 3, 1, 1, 10) );
// frame.getContentPane().add( new TimerAnimation(10, 10, 3, 0, 1, 1, 10) );
}
}
You can add a KeyListener to the panel and it will operate independently of the image animation.

How to Zoom specific area of Image on Canvas in Swing

I want to Zoom specific area on image. which is selected by the user. image display on canvas using Swing. i already done full image zoom on canvas but can't implement specific area zoom.
please help

Canvas is awt not swing. Try JPanel instead. Example.
But if you already done full image zoom, try to make the same on a sub-image.
BufferedImage.getSubimage(x, y, w, h);
EDIT
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class Example {
private Point startPoint = new Point(0, 0);
private Point rectLocale = new Point();
private Dimension rectSize = new Dimension();
private int zoom = 80;
private BufferedImage capture = null;
private BufferedImage raw;
public Example() throws Exception {
raw = new Robot().createScreenCapture(new Rectangle(
Toolkit.getDefaultToolkit().getScreenSize()));
MouseBehavior behavior = new MouseBehavior();
JPanel b = new JPanel() {
private static final long serialVersionUID = 1L;
#Override
public Dimension getMinimumSize() {
return new Dimension(500, 500);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(500, 500);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = ((Graphics2D) g);
g2d.drawImage(raw, 0, 0, null);
if (capture != null) {
int width2 = (int) (rectSize.width + rectSize.width * (zoom / 500d));
int height2 = (int) (rectSize.height + rectSize.height * (zoom / 500d));
int x2 = rectLocale.x - ((width2 - rectSize.width) / 2);
int y2 = rectLocale.y - ((height2 - rectSize.height) / 2);
Image scaledInstance = capture.getScaledInstance(
width2, height2, Image.SCALE_AREA_AVERAGING);
g2d.drawImage(scaledInstance, x2, y2, null);
g2d.drawRect(x2, y2, width2, height2);
} else {
g2d.draw(new Rectangle(rectLocale, rectSize));
}
}
};
b.addMouseMotionListener(behavior);
b.addMouseListener(behavior);
b.addMouseWheelListener(behavior);
JFrame f = new JFrame();
f.setLocation(10, 10);
f.setDefaultCloseOperation(3);
f.add(b);
f.pack();
f.setVisible(true);
}
private class MouseBehavior extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
startPoint = e.getPoint();
rectLocale = new Point();
rectSize = new Dimension();
capture = null;
if (e.getSource() instanceof JComponent) {
((JComponent) e.getSource()).repaint();
}
}
#Override
public void mouseDragged(MouseEvent e) {
Point currentPoint = e.getPoint();
rectSize.width = Math.abs(currentPoint.x - startPoint.x);
rectSize.height = Math.abs(currentPoint.y - startPoint.y);
if (e.isShiftDown()) {
rectSize.width = rectSize.height = Math.min(
rectSize.width, rectSize.height);
int dx = startPoint.x - rectSize.width;
int dy = startPoint.y - rectSize.height;
rectLocale.x = startPoint.x < currentPoint.x ? startPoint.x
: Math.max(dx, dy);
rectLocale.y = startPoint.y < currentPoint.y ? startPoint.y
: Math.min(dx, dy);
} else {
rectLocale.x = Math.min(currentPoint.x, startPoint.x);
rectLocale.y = Math.min(currentPoint.y, startPoint.y);
}
if (e.getSource() instanceof JComponent) {
((JComponent) e.getSource()).repaint();
}
}
#Override
public void mouseReleased(MouseEvent e) {
if (rectSize.width <= 0 || rectSize.height <= 0) {
capture = null;
} else {
capture = raw.getSubimage(Math.max(0, rectLocale.x),
Math.max(0, rectLocale.y), rectSize.width, rectSize.height);
}
if (e.getSource() instanceof JComponent) {
((JComponent) e.getSource()).repaint();
}
}
#Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoom = Math.min(2000, Math.max(0, zoom + e.getUnitsToScroll() * 10));
if (e.getSource() instanceof JComponent) {
((JComponent) e.getSource()).repaint();
}
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
Example example = new Example();
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
}

Why it doesn't draw an animated curve?

This is my class which I found on the Internet. It was originally an applet but I don't want to use it as an applet so I changed some methods (such as init() to a constructor).
However, it doesn't work. Would you please help me?
SignInFrame Frame:
public class SignInFrame extends javax.swing.JFrame {
Panel panel;
/** Creates new form SignInFrame */
public SignInFrame() {
initComponents();
}
public void init() {
getContentPane().add(panel = new Panel());
}
public void start() {
panel.start();
}
public void stop() {
panel.stop();
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new SignInFrame().setVisible(true);
}
});
}}
Panel Dialog:
package ClientGUI;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Paint;
import java.awt.RenderingHints;
import java.awt.geom.GeneralPath;
import java.awt.image.BufferedImage;
/**
*
* #author ICC
*/
public class Panel extends javax.swing.JPanel implements Runnable{
private Thread thread;
private BufferedImage bimg;
private static final int NUMPTS = 6;
// solid line stoke
protected BasicStroke solid = new BasicStroke(10.0f,
BasicStroke.CAP_BUTT, BasicStroke.JOIN_ROUND);
// dashed line stroke
protected BasicStroke dashed = new BasicStroke(10.0f,
BasicStroke.CAP_BUTT, BasicStroke.JOIN_ROUND, 10, new float[] {5}, 0);
private float animpts[] = new float[NUMPTS * 2];
private float deltas[] = new float[NUMPTS * 2];
protected Paint fillPaint, drawPaint;
// indicates whether or not to fill shape
protected boolean doFill = true;
// indicates whether or not to draw shape
protected boolean doDraw = true;
protected GradientPaint gradient;
protected BasicStroke stroke;
public Panel() {
setBackground(Color.white);
gradient = new GradientPaint(0,0,Color.red,200,200,Color.yellow);
fillPaint = gradient;
drawPaint = Color.blue;
stroke = solid;
}
// generates new points for the path
public void animate(float[] pts, float[] deltas, int i, int limit) {
float newpt = pts[i] + deltas[i];
if (newpt <= 0) {
newpt = -newpt;
deltas[i] = (float) (Math.random() * 4.0 + 2.0);
} else if (newpt >= (float) limit) {
newpt = 2.0f * limit - newpt;
deltas[i] = - (float) (Math.random() * 4.0 + 2.0);
}
pts[i] = newpt;
}
/*
* generates random points with the specified surface width
* and height for the path
*/
public void reset(int w, int h) {
for (int i = 0; i < animpts.length; i += 2) {
animpts[i + 0] = (float) (Math.random() * w);
animpts[i + 1] = (float) (Math.random() * h);
deltas[i + 0] = (float) (Math.random() * 6.0 + 4.0);
deltas[i + 1] = (float) (Math.random() * 6.0 + 4.0);
if (animpts[i + 0] > w / 2.0f) {
deltas[i + 0] = -deltas[i + 0];
}
if (animpts[i + 1] > h / 2.0f) {
deltas[i + 1] = -deltas[i + 1];
}
}
gradient = new GradientPaint(0,0,Color.red,w*.7f,h*.7f,Color.yellow);
}
// calls animate for every point in animpts
public void step(int w, int h) {
for (int i = 0; i < animpts.length; i += 2) {
animate(animpts, deltas, i + 0, w);
animate(animpts, deltas, i + 1, h);
}
}
// sets the points of the path and draws and fills the path
public void drawDemo(int w, int h, Graphics2D g2) {
float[] ctrlpts = animpts;
int len = ctrlpts.length;
float prevx = ctrlpts[len - 2];
float prevy = ctrlpts[len - 1];
float curx = ctrlpts[0];
float cury = ctrlpts[1];
float midx = (curx + prevx) / 2.0f;
float midy = (cury + prevy) / 2.0f;
GeneralPath gp = new GeneralPath(GeneralPath.WIND_NON_ZERO);
gp.moveTo(midx, midy);
for (int i = 2; i <= ctrlpts.length; i += 2) {
float x1 = (midx + curx) / 2.0f;
float y1 = (midy + cury) / 2.0f;
prevx = curx;
prevy = cury;
if (i < ctrlpts.length) {
curx = ctrlpts[i + 0];
cury = ctrlpts[i + 1];
} else {
curx = ctrlpts[0];
cury = ctrlpts[1];
}
midx = (curx + prevx) / 2.0f;
midy = (cury + prevy) / 2.0f;
float x2 = (prevx + midx) / 2.0f;
float y2 = (prevy + midy) / 2.0f;
gp.curveTo(x1, y1, x2, y2, midx, midy);
}
gp.closePath();
if (doDraw) {
g2.setPaint(drawPaint);
g2.setStroke(stroke);
g2.draw(gp);
}
if (doFill) {
if (fillPaint instanceof GradientPaint) {
fillPaint = gradient;
}
g2.setPaint(fillPaint);
g2.fill(gp);
}
}
public Graphics2D createGraphics2D(int w, int h) {
Graphics2D g2 = null;
if (bimg == null || bimg.getWidth() != w || bimg.getHeight() != h) {
bimg = (BufferedImage) createImage(w, h);
reset(w, h);
}
g2 = bimg.createGraphics();
g2.setBackground(getBackground());
g2.clearRect(0, 0, w, h);
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
return g2;
}
public void paint(Graphics g) {
Dimension d = getSize();
step(d.width, d.height);
Graphics2D g2 = createGraphics2D(d.width, d.height);
drawDemo(d.width, d.height, g2);
g2.dispose();
if (bimg != null) {
g.drawImage(bimg, 0, 0, this);
}
}
public void start() {
thread = new Thread(this);
thread.setPriority(Thread.MIN_PRIORITY);
thread.start();
}
public synchronized void stop() {
thread = null;
}
public void run() {
Thread me = Thread.currentThread();
while (thread == me) {
repaint();
try {
Thread.sleep(10);
} catch (Exception e) { break; }
}
thread = null;
}
public static void main(String argv[]) {
SignInFrame n = new SignInFrame();
n.start();
}}

In your SignInFrame constructor, you call initComponents(), but that does not exist. I think you mean to call init(). Also your JFrame does not have a size set, when I ran this under linux (Java 1.6), it worked but was tiny, you should add a setSize call.
Try it with these edits:
public class SignInFrame extends javax.swing.JFrame {
Panel panel;
/** Creates new form SignInFrame */
public SignInFrame() {
setSize (600,600);
init();
}
public void init() {
getContentPane().add(panel = new Panel());
start();
}
public void start() {
panel.start();
}
public void stop() {
panel.stop();
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new SignInFrame().setVisible(true);
}
});
}
}