Hello,
i don't know if am able to post here or not, but i finally find the "correct" way to rotate an object and make it move toward the its rotation direction, and i decided to share it in case someone else has find himself facing the same problem i have for this whole week.
[if you found any error please correct me]
so,
1st thing you need to know is the "head" of your object, if you draw a rectangle and its rotation angle is still 0, which mean you didn't rotate it yet, then the head is filled rectangle like this picture show
i don't know if am the only one who made that error, but i was thinking that the head is the upper line
anyway, here is a very simple example on how to rotate a square and make it move forward and backward (car movement )
this is the Hero class, the object that we will rotate
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|
package rot;
public class Hero {
private double x, y, a; private int w, h;
public Hero(double x, double y, double a, int w, int h) {
this.x = x;
this.y = y;
this.a = a;
this.w = w;
this.h = h;
}
public double getX() {
return x;
}
public double getY() {
return y;
}
public double getA() {
return a;
}
public int getW() {
return w;
}
public int getH() {
return h;
}
public void setA(int aa) {
a = Math.toRadians(aa);
}
public void moveForward() {
x += Math.cos(a);
y += Math.sin(a);
}
public void moveBackword() {
x -= Math.cos(a);
y -= Math.sin(a);
}
}
|
this is the Board class, it have the game loop, the game control key and the game logic
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| package rot;
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.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.AffineTransform;
import javax.swing.JPanel;
public class Board extends JPanel implements Runnable {
private Thread loop;
private Hero hero;
private int tmpAngle;
private boolean moveForward, moveBackward;
public Board() {
init();
addKeyListener(new Controll());
setFocusable(true);
setBackground(new Color(0, 50, 100));
setDoubleBuffered(true);
setFocusable(true);
}
private void init() {
hero = new Hero(400, 300, 0, 70, 50);
tmpAngle = 0;
moveForward = moveBackward = false;
loop = new Thread(this);
loop.start();
}
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
AffineTransform old = g2d.getTransform();
g2d.setColor(Color.white);
g2d.rotate(hero.getA(), hero.getX() + hero.getW() / 2, hero.getY()
+ hero.getH() / 2);
g2d.drawRect((int) hero.getX(), (int) hero.getY(), hero.getW(),
hero.getH());
g2d.fillRect((int) hero.getX() + hero.getW(), (int) hero.getY() + 10,
10, 30);
g2d.setTransform(old);
}
public void play() {
if (tmpAngle > 360) {
tmpAngle = 0;
} else if (tmpAngle < 0) {
tmpAngle = 360;
}
hero.setA(tmpAngle);
if (moveForward) {
hero.moveForward();
} else if (moveBackward) {
hero.moveBackword();
}
}
@Override
public void run() {
while (true) {
repaint();
play();
try {
loop.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private class Controll extends KeyAdapter {
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == e.VK_UP) {
moveForward = true;
}
if (e.getKeyCode() == e.VK_DOWN) {
moveBackward = true;
}
if (e.getKeyCode() == e.VK_LEFT) {
tmpAngle -= 5;
}
if (e.getKeyCode() == e.VK_RIGHT) {
tmpAngle += 5;
}
}
public void keyReleased(KeyEvent e) {
if (e.getKeyCode() == e.VK_UP) {
moveForward = false;
}
if (e.getKeyCode() == e.VK_DOWN) {
moveBackward = false;
}
if (e.getKeyCode() == e.VK_LEFT) {
tmpAngle -= 0;
}
if (e.getKeyCode() == e.VK_RIGHT) {
tmpAngle += 0;
}
}
}
} |
and finally this is the frame class, the one that have the main class
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package rot;
import javax.swing.JFrame;
public class RotateME extends JFrame {
private final int width = 800, height = 600;
public RotateME() {
add(new Board());
setTitle("rotate me please");
setSize(width, height);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(true);
setVisible(true);
}
public static void main(String[] args) {
new RotateME();
}
}
|
i hope what i said is correct and can be helpful for new developers like me
thank you
