【发布时间】：2013-11-20 16:57:36
【问题描述】：
我对 Java 有一点了解，我决定参加一门课程来学习更多知识，并且我被分配了一个相当简单的任务。我已经完成了大部分工作，我知道剩下的事情一定很简单，但我似乎无法完全理解。到目前为止，我已经能够成功创建一个有 1 个弹跳球的程序，但我现在想允许用户输入要弹跳的球的数量。我在 Ball 类中尝试了几个不同的循环，但它们都不起作用。有人愿意快速伸出援手吗？我几乎可以肯定它需要一个 Array 或 ArrayList 并将球存储在其中，但我还没有找到一个可行的解决方案。我在网站上查看过类似的其他问题，但没有一个能完全解决我的问题。如果您能提供帮助，谢谢！
主类：
public class mainClass {
/**
/**
* Frame to hold a bouncing ball panel, implemented in the BallPanel class.
* Controls the animation of the ball via pauses and calls to BallPanel's move
* method.
*
* @author Michael Peterson modified by Mr O Aug 2012
*/
public static class BallTest extends JFrame {
// size of the window
private static final int WINDOW_WIDTH = 500;
private static final int WINDOW_HEIGHT = 300;
// panel containing the bouncing ball
private BallPanel ballPanel;
/**
* Pause command used to control the speed of the bouncing ball animation.
* Currently pauses for 20 ms. Use smaller values for faster animation and
* vice versa.
*/
public static void pause() {
try {
Thread.sleep(20); // pause for 20 ms
} catch (Exception e) {
System.out.println(e);
e.printStackTrace();
}//end of catch
}//end of pause method
/**
* Creates a new instance of BallTest
*/
public BallTest() {
super("Bouncing Ball"); // set frame name
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
setLayout(new BorderLayout());
ballPanel = new BallPanel();
add(ballPanel);
center(this);
setVisible(true);
// infinite animation loop, program halts when window is closed.
while (true) {
pause();
ballPanel.move(ballPanel);
}//end of while loop of animation
} //end of BallTest Constructor
/**
* Helper routine to center a frame on the screen (will cause problems if
* frame is bigger than the screen!)
*/
public static void center(JFrame frame) {
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
Point center = ge.getCenterPoint();
int w = frame.getWidth();
int h = frame.getHeight();
int x = center.x - w / 2, y = center.y - h / 2;
frame.setBounds(x, y, w, h);
frame.validate();
}//end of center method
}//end of BallPanel Class
public static void main(String[] args) {
BallTest t = new BallTest(); //make a BallTest object
}//end of main method
}//end of Fall2012Lab11StarterCode class
球类：
public class Ball extends JPanel {
private int bxCoord; //the ball's x coordinate
private int byCoord; //the ball's y coordinate
private int bHeight; //the ball's height
private int bWidth; //the ball's weight
private int bRise; //the ball's y change
private int bRun; //the ball's x change
private Color bColor; //the ball's color
//Constructor
public Ball() {
bxCoord = setStartBxCoord();
byCoord = setStartByCoord();
bHeight = setStartBHeight();
bWidth = setStartBWidth();
bRise = setStartBRise();
bRun = setStartBRun();
bColor = setStartColor();
}
/**
* The setters, getters, and initial value for the ball's x coordinate
*/
public void setBxCoord(int xCoord) {
bxCoord = xCoord;
}
public int setStartBxCoord() {
int xCoord;
xCoord = (int) (Math.random() * 51);
return xCoord;
}
public int getBxCoord() {
return bxCoord;
}
/**
* The setters, getters, and initial value for the ball's y coordinate
*/
public void setByCoord(int yCoord) {
bxCoord = yCoord;
}
public int setStartByCoord() {
int yCoord;
yCoord = (int) (Math.random() * 51);
return yCoord;
}
public int getByCoord() {
return byCoord;
}
/**
* The setters, getters, and initial value for the ball's x height
*/
public void setBHeight(int height) {
bHeight = height;
}
public int setStartBHeight() {
int height;
height = (int) (10 + Math.random() * 11);
return height;
}
public int getBHeight() {
return bHeight;
}
public void setBWidth(int width) {
bWidth = width;
}
/**
* The setters, getters, and initial value for the ball's x width
*/
public int setStartBWidth() {
int width;
width = (int) (10 + Math.random() * 11);
return width;
}
public int getBWidth() {
return bWidth;
}
/**
* The setters, getters, and initial value for the ball's rise
*/
public void setBRise(int rise) {
bRise = rise;
}
public int setStartBRise() {
int rise;
rise = (int) (Math.random() * 11);
return rise;
}
public int getBRise() {
return bRise;
}
/**
* The setters, getters, and initial value for the ball's run
*/
public void setBRun(int run) {
bRun = run;
}
public int setStartBRun() {
int run;
run = (int) (Math.random() * 11);
return run;
}
public int getBRun() {
return bRun;
}
/**
* The movement of the ball in the x and y direction
*/
public void moveX(){
bxCoord += bRun;
}
public void moveY(){
byCoord += bRise;
}
/**
* The setters, getters, and initial value for the ball's color
*/
public void setColor(Color color) {
bColor = color;
}
public Color setStartColor() {
int red = (int) (Math.random() * 256);
int green = (int) (Math.random() * 256);
int blue = (int) (Math.random() * 256);
Color ranColor = new Color(red, green, blue);
return ranColor;
}
public Color getbColor() {
return bColor;
}
/**
* Computes the next position for the balls and updates their positions.
*/
public void move(BallPanel ballPanel) {
// If ball is approaching a wall, reverse direction
if ((getBxCoord() < (0 - getBRun())) || (getBxCoord() > (ballPanel.getWidth() - getBWidth()))) {
setBRun(-getBRun());
}
if ((getByCoord() < (0 - getBRise())) || (getByCoord() > (ballPanel.getHeight() - getBHeight()))) {
setBRise(-getBRise());
}
// "Move" ball according to values in rise and run
moveX();
moveY();
} // end method move
}//end of Ball Class
球面板类：
public class BallPanel extends JPanel {
Ball ball = new Ball(); //creat a ball.
/**
* Creates a new instance of BallPanel
*/
public BallPanel() {
super();
}
/**
* The move method moves the ball and repaints the panel
* PreCondtion: A panel containing a ball has been created
* PostCondition: The position of a ball on the panel has moved. The panell
* is repainted with the ball in the new position.
* @param ballPanel The name of the panel on which the ball is found
*/
public void move(BallPanel ballPanel) {
ball.move(ballPanel);
repaint();
}
/**
* Paints the balls at their current positions within the panel.
* PreCondition: A graphics object has been created and needs to be displayed
* PostCondition: The graphics object g has been displayed
* @param g The graphic object to be displayed
*/
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.black); // set color black
g.fillRect(0, 0, getWidth(), getHeight()); // paint background
// Paint the Ball
g.setColor(ball.getbColor());
g.fillOval(ball.getBxCoord(), ball.getByCoord(),
ball.getBWidth(), ball.getBHeight());
}//end of paintComponent method
}//end of BallPanel class
【问题讨论】：