[Thread] aide pour comprendre un exemple
Bonjour, j'ai le code java ci-dessous pour apprendre à utilisez les threads.
Mais j'ai 2-3 problèmes, des zone d'ombre que je ne comprend pas.
Code:
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| import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;
public class BounceThread {
public static void main(String[] args) {
JFrame frame = new BounceFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
class BallRunnable implements Runnable {
public BallRunnable(Ball aBall, Component aComponent) {
ball = aBall;
component = aComponent;
}
public void run() {
try {
for (int i = 1; i <= STEPS; i++) {
ball.move(component.getBounds());
component.repaint();
Thread.sleep(DELAY);
}
} catch (InterruptedException e) {
}
}
private Ball ball;
private Component component;
public static final int STEPS = 1000;
public static final int DELAY = 5;
}
class Ball {
public void move(Rectangle2D bounds) {
x += dx;
y += dy;
if (x < bounds.getMinX()) {
x = bounds.getMinX();
dx = -dx;
}
if (x + XSIZE >= bounds.getMaxX()) {
x = bounds.getMaxX() - XSIZE;
dx = -dx;
}
if (y < bounds.getMinY()) {
y = bounds.getMinY();
dy = -dy;
}
if (y + YSIZE >= bounds.getMaxY()) {
y = bounds.getMaxY() - YSIZE;
dy = -dy;
}
}
public Ellipse2D getShape() {
return new Ellipse2D.Double(x, y, XSIZE, YSIZE);
}
private static final int XSIZE = 15;
private static final int YSIZE = 15;
private double x = 0;
private double y = 0;
private double dx = 1;
private double dy = 1;
}
class BallPanel extends JPanel {
public void add(Ball b) {
balls.add(b);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
for (Ball b : balls) {
g2.fill(b.getShape());
}
}
private ArrayList<Ball> balls = new ArrayList<Ball>();
}
class BounceFrame extends JFrame {
public BounceFrame() {
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
setTitle("BounceThread");
panel = new BallPanel();
add(panel, BorderLayout.CENTER);
JPanel buttonPanel = new JPanel();
addButton(buttonPanel, "Start", new ActionListener() {
public void actionPerformed(ActionEvent event) {
addBall();
}
});
addButton(buttonPanel, "Close", new ActionListener() {
public void actionPerformed(ActionEvent event) {
System.exit(0);
}
});
add(buttonPanel, BorderLayout.SOUTH);
}
public void addButton(Container c, String title, ActionListener listener) {
JButton button = new JButton(title);
c.add(button);
button.addActionListener(listener);
}
public void addBall() {
Ball b = new Ball();
panel.add(b);
Runnable r = new BallRunnable(b, panel);
Thread t = new Thread(r);
t.start();
}
private BallPanel panel;
public static final int DEFAULT_WIDTH = 450;
public static final int DEFAULT_HEIGHT = 350;
public static final int STEPS = 1000;
public static final int DELAY = 3;
} |
Voilà le morceau de code que je ne comprend pas.
Code:
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| public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
for (Ball b : balls) {
g2.fill(b.getShape());
}
} |
Quand cette méthode est-elle appelée et que représente g ?
merci
[ Modéré par Bulbo ]
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