我想实现球物理，而且作为新手，我在教程中调整代码 http://adam21.web.officelive.com/Documents/JavaPhysicsTutorial.pdf。
我试着尽我所能， 但是我无法在代码中应用所有物理现象，有人可以告诉我，我错了或者我还在做一些愚蠢的编程错误。
当我没有调用弹跳方法并且我无法利用弹跳方法并且球向左侧移动而不是在地板上下降/结束时，球正在移动，
有些人可以推荐一些更好的方法或类似的简单方法来完成将物理应用于两个球或更多球的交互性任务。
这是代码;
import java.awt.*;
public class AdobeBall {
protected int radius = 20;
protected Color color;
// ... Constants
final static int DIAMETER = 40;
// ... Instance variables
private int m_x; // x and y coordinates upper left
private int m_y;
private double dx = 3.0; // delta x and y
private double dy = 6.0;
private double m_velocityX; // Pixels to move each time move() is called.
private double m_velocityY;
private int m_rightBound; // Maximum permissible x, y values.
private int m_bottomBound;
public AdobeBall(int x, int y, double velocityX, double velocityY,
Color color1) {
super();
m_x = x;
m_y = y;
m_velocityX = velocityX;
m_velocityY = velocityY;
color = color1;
}
public double getSpeed() {
return Math.sqrt((m_x + m_velocityX - m_x) * (m_x + m_velocityX - m_x)
+ (m_y + m_velocityY - m_y) * (m_y + m_velocityY - m_y));
}
public void setSpeed(double speed) {
double currentSpeed = Math.sqrt(dx * dx + dy * dy);
dx = dx * speed / currentSpeed;
dy = dy * speed / currentSpeed;
}
public void setDirection(double direction) {
m_velocityX = (int) (Math.cos(direction) * getSpeed());
m_velocityY = (int) (Math.sin(direction) * getSpeed());
}
public double getDirection() {
double h = ((m_x + dx - m_x) * (m_x + dx - m_x))
+ ((m_y + dy - m_y) * (m_y + dy - m_y));
double a = (m_x + dx - m_x) / h;
return a;
}
// ======================================================== setBounds
public void setBounds(int width, int height) {
m_rightBound = width - DIAMETER;
m_bottomBound = height - DIAMETER;
}
// ============================================================== move
public void move() {
double gravAmount = 0.02;
double gravDir = 90; // The direction for the gravity to be in.
// ... Move the ball at the give velocity.
m_x += m_velocityX;
m_y += m_velocityY;
// ... Bounce the ball off the walls if necessary.
if (m_x < 0) { // If at or beyond left side
m_x = 0; // Place against edge and
m_velocityX = -m_velocityX;
} else if (m_x > m_rightBound) { // If at or beyond right side
m_x = m_rightBound; // Place against right edge.
m_velocityX = -m_velocityX;
}
if (m_y < 0) { // if we're at top
m_y = 0;
m_velocityY = -m_velocityY;
} else if (m_y > m_bottomBound) { // if we're at bottom
m_y = m_bottomBound;
m_velocityY = -m_velocityY;
}
// double speed = Math.sqrt((m_velocityX * m_velocityX)
// + (m_velocityY * m_velocityY));
// ...Friction stuff
double fricMax = 0.02; // You can use any number, preferably less than 1
double friction = getSpeed();
if (friction > fricMax)
friction = fricMax;
if (m_velocityX >= 0) {
m_velocityX -= friction;
}
if (m_velocityX <= 0) {
m_velocityX += friction;
}
if (m_velocityY >= 0) {
m_velocityY -= friction;
}
if (m_velocityY <= 0) {
m_velocityY += friction;
}
// ...Gravity stuff
m_velocityX += Math.cos(gravDir) * gravAmount;
m_velocityY += Math.sin(gravDir) * gravAmount;
}
public Color getColor() {
return color;
}
public void setColor(Color newColor) {
color = newColor;
}
// ============================================= getDiameter, getX, getY
public int getDiameter() {
return DIAMETER;
}
public double getRadius() {
return radius; // radius should be a local variable in Ball.
}
public int getX() {
return m_x;
}
public int getY() {
return m_y;
}
}
使用adobeBall：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class AdobeBallImplementation implements Runnable {
private static final long serialVersionUID = 1L;
private volatile boolean Play;
private long mFrameDelay;
private JFrame frame;
private MyKeyListener pit;
/** true means mouse was pressed in ball and still in panel. */
private boolean _canDrag = false;
private static final int MAX_BALLS = 50; // max number allowed
private int currentNumBalls = 2; // number currently active
private AdobeBall[] ball = new AdobeBall[MAX_BALLS];
public AdobeBallImplementation(Color ballColor) {
frame = new JFrame("simple gaming loop in java");
frame.setSize(400, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pit = new MyKeyListener();
pit.setPreferredSize(new Dimension(400, 400));
frame.setContentPane(pit);
ball[0] = new AdobeBall(34, 150, 7, 2, Color.YELLOW);
ball[1] = new AdobeBall(50, 50, 5, 3, Color.BLUE);
frame.pack();
frame.setVisible(true);
frame.setBackground(Color.white);
start();
frame.addMouseListener(pit);
frame.addMouseMotionListener(pit);
}
public void start() {
Play = true;
Thread t = new Thread(this);
t.start();
}
public void stop() {
Play = false;
}
public void run() {
while (Play == true) {
// bounce(ball[0],ball[1]);
runball();
pit.repaint();
try {
Thread.sleep(mFrameDelay);
} catch (InterruptedException ie) {
stop();
}
}
}
public void drawworld(Graphics g) {
for (int i = 0; i < currentNumBalls; i++) {
g.setColor(ball[i].getColor());
g.fillOval(ball[i].getX(), ball[i].getY(), 40, 40);
}
}
public double pointDistance (double x1, double y1, double x2, double y2) {
return Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
}
public void runball() {
while (Play == true) {
try {
for (int i = 0; i < currentNumBalls; i++) {
for (int j = 0; j < currentNumBalls; j++) {
if (pointDistance(ball[i].getX(), ball[i].getY(),
ball[j].getX(), ball[j].getY()) < ball[i]
.getRadius()
+ ball[j].getRadius() + 2) {
// bounce(ball[i],ball[j]);
ball[i].setBounds(pit.getWidth(), pit.getHeight());
ball[i].move();
pit.repaint();
}
}
}
try {
Thread.sleep(50);
} catch (Exception e) {
System.exit(0);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public static double pointDirection(int x1, int y1, int x2, int y2) {
double H = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1)); // The
// hypotenuse
double x = x2 - x1; // The opposite
double y = y2 - y1; // The adjacent
double angle = Math.acos(x / H);
angle = angle * 57.2960285258;
if (y < 0) {
angle = 360 - angle;
}
return angle;
}
public static void bounce(AdobeBall b1, AdobeBall b2) {
if (b2.getSpeed() == 0 && b1.getSpeed() == 0) {
// Both balls are stopped.
b1.setDirection(pointDirection(b1.getX(), b1.getY(), b2.getX(), b2
.getY()));
b2.setDirection(pointDirection(b2.getX(), b2.getY(), b1.getX(), b1
.getY()));
b1.setSpeed(1);
b2.setSpeed(1);
} else if (b2.getSpeed() == 0 && b1.getSpeed() != 0) {
// B1 is moving. B2 is stationary.
double angle = pointDirection(b1.getX(), b1.getY(), b2.getX(), b2
.getY());
b2.setSpeed(b1.getSpeed());
b2.setDirection(angle);
b1.setDirection(angle - 90);
} else if (b1.getSpeed() == 0 && b2.getSpeed() != 0) {
// B1 is moving. B2 is stationary.
double angle = pointDirection(b2.getX(), b2.getY(), b1.getX(), b1
.getY());
b1.setSpeed(b2.getSpeed());
b1.setDirection(angle);
b2.setDirection(angle - 90);
} else {
// Both balls are moving.
AdobeBall tmp = b1;
double angle = pointDirection(b2.getX(), b2.getY(), b1.getX(), b1
.getY());
double origangle = b1.getDirection();
b1.setDirection(angle + origangle);
angle = pointDirection(tmp.getX(), tmp.getY(), b2.getX(), b2.getY());
origangle = b2.getDirection();
b2.setDirection(angle + origangle);
}
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
new AdobeBallImplementation(Color.red);
}
});
}
}
* 编辑： *确定从这个论坛使用新的重力方法分割代码：此代码也不起作用球不在场：
public void mymove() {
m_x += m_velocityX;
m_y += m_velocityY;
if (m_y + m_bottomBound > 400) {
m_velocityY *= -0.981;
// setY(400 - m_bottomBound);
m_y = 400 - m_bottomBound;
}
// ... Bounce the ball off the walls if necessary.
if (m_x < 0) { // If at or beyond left side
m_x = 0; // Place against edge and
m_velocityX = -m_velocityX;
} else if (m_x > m_rightBound) { // If at or beyond right side
m_x = m_rightBound - 20; // Place against right edge.
m_velocityX = -m_velocityX;
}
if (m_y < 0) { // if we're at top
m_y = 1;
m_velocityY = -m_velocityY;
} else if (m_y > m_bottomBound) { // if we're at bottom
m_y = m_bottomBound - 20;
m_velocityY = -m_velocityY;
}
}
非常感谢任何纠正和帮助。
jibby
答案 0 :(得分：5)
目前我无法运行java，所以我无法测试你的代码，但我注意到了几件事：
修改：
这个重力代码是错误的：
if (m_y + m_bottomBound > 400) {
m_velocityY *= -0.981;
// setY(400 - m_bottomBound);
m_y = 400 - m_bottomBound;
}
首先，您使用400作为“神奇数字”;我不知道它代表什么。然后，您将效果限制在靠近屏幕顶部的区域，原因不明确。在函数结束时，您以一种毫无意义的方式更改m_y。而且（也许）最糟糕的是，你有重力倒转和乘以垂直速度，这不是引力的工作方式。
请改为尝试：
// You will have to adjust this. Start with a small value and increase it until
// you see an effect.
final static double GRAVITY = 0.1;
// Note that +y is down, so accelerating downward means increasing vY
m_velocityY += GRAVITY;
答案 1 :(得分：2)
好的，还没有解决问题。但有些事情可能有所帮助：
1 - Math.sin / cos取弧度的角度。 （这可能有助于痘痘）。 - AdobeBall
2 - 你必须为每次调用move（）计算gravDir，因为m_velocityX / Y可能有改变方向 - AdobeBall
3 - 你在runball（）中的主循环使用同一个球两次并与自身比较...在第二个循环中使用j = i + 1
4 - 在线程循环中调用runball（）。所以无论如何我都希望球能够移动....不只是你打电话给弹跳（）。我没错？
您可以更正您的代码，然后重试。并发布新闻！ ：）