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copied!<p>After making changes based on user suggestions I have taken the following code a few steps further by introducing single/double click recognition. Why are the balls being created in the top left corner and not where the mouse is clicked?</p> <h3>BouncingBalls.java</h3> <pre class="lang-java prettyprint-override"><code>import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Toolkit; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import java.util.ArrayList; import java.util.List; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.Timer; public class BouncingBalls extends JPanel implements MouseListener { protected List<RandomBall> randomBalls = new ArrayList<RandomBall>(20); protected List<VerticalBall> verticalBalls = new ArrayList<VerticalBall>(20); private Container container; private DrawCanvas canvas; private Boolean doubleClick = false; private final Integer waitTime = (Integer) Toolkit.getDefaultToolkit() .getDesktopProperty("awt.multiClickInterval"); private static int canvasWidth = 500; private static int canvasHeight = 500; public static final int UPDATE_RATE = 30; int count = 0; public static int random(int maxRange) { return (int) Math.round((Math.random() * maxRange)); } public BouncingBalls(int width, int height) { canvasWidth = width; canvasHeight = height; container = new Container(); canvas = new DrawCanvas(); this.setLayout(new BorderLayout()); this.add(canvas, BorderLayout.CENTER); this.addMouseListener(this); start(); } public void start() { Thread t = new Thread() { public void run() { while (true) { update(); repaint(); try { Thread.sleep(1000 / UPDATE_RATE); } catch (InterruptedException e) { } } } }; t.start(); } public void update() { for (RandomBall ball : randomBalls) { ball.ballBounce(container); } for (VerticalBall ball : verticalBalls) { ball.verticalBounce(container); } } class DrawCanvas extends JPanel { public void paintComponent(Graphics g) { super.paintComponent(g); container.draw(g); for (RandomBall ball : randomBalls) { ball.draw(g); } for (VerticalBall ball : verticalBalls) { ball.draw(g); } } public Dimension getPreferredSize() { return (new Dimension(canvasWidth, canvasHeight)); } } public static void main(String[] args) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { JFrame f = new JFrame("Stack Answer 2"); f.setDefaultCloseOperation(f.EXIT_ON_CLOSE); f.setContentPane(new BouncingBalls(canvasHeight, canvasWidth)); f.pack(); f.setVisible(true); } }); } @Override public void mouseClicked(MouseEvent e) { // TODO Auto-generated method stub } @Override public void mouseEntered(MouseEvent e) { // TODO Auto-generated method stub } @Override public void mouseExited(MouseEvent e) { // TODO Auto-generated method stub } @Override public void mousePressed(MouseEvent e) { if (e.getClickCount() >= 2) { doubleClick = true; verticalBalls.add(new VerticalBall(getX(), getY(), canvasWidth, canvasHeight)); System.out.println("double click"); } else { Timer timer = new Timer(waitTime, new ActionListener() { public void actionPerformed(ActionEvent e) { if (doubleClick) { /* we are the first click of a double click */ doubleClick = false; } else { count++; randomBalls.add(new RandomBall(getX(), getY(), canvasWidth, canvasHeight)); /* the second click never happened */ System.out.println("single click"); } } }); timer.setRepeats(false); timer.start(); } } @Override public void mouseReleased(MouseEvent e) { // TODO Auto-generated method stub } } </code></pre> <h3>RandomBall.java</h3> <pre class="lang-java prettyprint-override"><code>import java.awt.Color; import java.awt.Graphics; public class RandomBall { public static int random(int maxRange) { return (int) Math.round((Math.random() * maxRange)); } private int x; private int y; private int canvasWidth = 500; private int canvasHeight = 500; private boolean leftRight; private boolean upDown; private int deltaX; private int deltaY; private int radius = 20; private int red = random(255); private int green = random(255); private int blue = random(255); RandomBall(int x, int y, int width, int height) { this(x, y, width, height, false, false); } RandomBall(int x, int y, int width, int height, boolean leftRight, boolean upDown) { this.x = x; this.y = y; this.canvasWidth = width; this.canvasHeight = height; this.leftRight = leftRight; this.upDown = upDown; updateDelta(); } public void draw(Graphics g) { g.setColor(new Color(red, green, blue)); g.fillOval((int) (x - radius), (int) (y - radius), (int) (2 * radius), (int) (2 * radius)); } private void updateDelta() { final int minimumMovement = 5; final int maxExtra = 10; deltaY = minimumMovement + (int) (Math.random() * maxExtra); deltaX = minimumMovement + (int) (Math.random() * maxExtra); } public void ballBounce(Container container) { // controls horizontal ball motion if (leftRight) { x += deltaX; if (x >= getWidth()) { leftRight = false; updateDelta(); } } else { x += -deltaX; if (x <= 0) { leftRight = true; updateDelta(); } } // controls vertical ball motion if (upDown) { y += deltaY; if (y >= getHeight()) { upDown = false; updateDelta(); } } else { y += -deltaY; if (y <= 0) { upDown = true; updateDelta(); } } } public void verticalBounce(Container container) { // controls vertical ball motion if (upDown) { y += deltaY; if (y >= getHeight()) { upDown = false; updateDelta(); } } else { y += -deltaY; if (y <= 0) { upDown = true; updateDelta(); } } } public int getX() { return x; } public int getY() { return y; } public int getWidth() { return canvasWidth; } public int getHeight() { return canvasHeight; } } </code></pre> <h3>VerticalBall.java</h3> <pre class="lang-java prettyprint-override"><code>import java.awt.Color; import java.awt.Graphics; public class VerticalBall { public static int random(int maxRange) { return (int) Math.round((Math.random() * maxRange)); } private int x; private int y; private int canvasWidth = 500; private int canvasHeight = 500; private boolean upDown; private int deltaY; private int radius = 20; private int red = random(255); private int green = random(255); private int blue = random(255); VerticalBall(int x, int y, int width, int height) { this(x, y, width, height, false); } VerticalBall(int x, int y, int width, int height, boolean upDown) { this.x = x; this.y = y; this.canvasWidth = width; this.canvasHeight = height; this.upDown = upDown; updateDelta(); } public void draw(Graphics g) { g.setColor(new Color(red, green, blue)); g.fillOval((int) (x - radius), (int) (y - radius), (int) (2 * radius), (int) (2 * radius)); } private void updateDelta() { final int minimumMovement = 5; final int maxExtra = 10; deltaY = minimumMovement + (int) (Math.random() * maxExtra); } public void verticalBounce(Container container) { // controls vertical ball motion if (upDown) { y += deltaY; if (y >= getHeight()) { upDown = false; updateDelta(); } } else { y += -deltaY; if (y <= 0) { upDown = true; updateDelta(); } } } public int getX() { return x; } public int getY() { return y; } public int getWidth() { return canvasWidth; } public int getHeight() { return canvasHeight; } } </code></pre> <h3>Container.java</h3> <pre class="lang-java prettyprint-override"><code>import java.awt.Color; import java.awt.Graphics; public class Container { private static final int HEIGHT = 500; private static final int WIDTH = 500; private static final Color COLOR = Color.WHITE; public void draw(Graphics g) { g.setColor(COLOR); g.fillRect(0, 0, WIDTH, HEIGHT); } } </code></pre>

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