我对 Java 完全陌生，我正在学习如何编写一个程序，该程序可以根据教授的讲座视频检测碰撞并做出反应。这是视频的链接。
我所有的代码都应该与他的演讲中的相似。我的错误似乎在 NewJFrame.java 文件中。为什么 ActionListener 不起作用？在此先感谢您的帮助。
/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package collisiondetection;
import java.awt.event.ActionListener;
import javafx.event.ActionEvent;
import javax.swing.Timer;
/**
*
* @author PC
*/
public class NewJFrame extends javax.swing.JFrame {
/**
* Creates new form NewJFrame
*/
public NewJFrame() {
initComponents();
bf = new BallField(getWidth(), getHeight());
add(bf);
pack();
njTimer = new Timer(1,
new ActionListener() {
public void actionPerformed(ActionEvent e) {
bf.detectCollision();
}
});
njTimer.start();
}
BallField bf;
Timer njTimer;
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 300, Short.MAX_VALUE)
);
pack();
}// </editor-fold>
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new NewJFrame().setVisible(true);
}
});
}
// Variables declaration - do not modify
// End of variables declaration
}
说“new ActionListener() {”的行带有下划线，我收到一条错误消息：
线程“主”java.lang.RuntimeException 中的异常：无法编译的源代码 - 不是抽象的，并且不会在碰撞检测的 java.awt.event.ActionListener 中覆盖抽象方法 actionPerformed(java.awt.event.ActionEvent)。NewJFrame.(NewJFrame .java:28) 在碰撞检测.Main.main(Main.java:20)
NewJFrame.java:28 指的是上面代码中“njTimer = new Timer(1”) 的行。
～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～
这是我的其他 .java 文件的代码以供参考。
主文件：
/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package collisiondetection;
/**
*
* @author PC
*/
public class Main {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
NewJFrame njf = new NewJFrame();
njf.setVisible(true);
}
}
BallField.java:
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package collisiondetection;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.JPanel;
/**
*
* @author PC
*/
public class BallField extends JPanel {
public BallField(int width, int height)
{
setSize(new Dimension(width, height));
setMinimumSize(new Dimension(width, height));
setMaximumSize(new Dimension(width, height));
bfList = new LinkedList<Shape>();
fillList();
}
public void detectCollision()
{
if(bfList.size() == 0)
{
fillList();
}
bfBall.move();
ListIterator iter = bfList.listIterator();
boolean collision = false;
while ((collision == false && iter.hasNext()))
{
Shape sh = (Shape) iter.next();
if(sh.collide(bfBall))
{
iter.remove();
collision = true;
}
}
}
public void PaintComponent(Graphics gfx)
{
int bWidth = getWidth();
int bHeight = getHeight();
gfx.setColor(bfBackground);
gfx.fillRect(0, 0, bWidth, bHeight);
ListIterator iter = bfList.listIterator();
while(iter.hasNext())
{
Shape sh = (Shape) iter.next();
sh.drawShape(gfx);
}
bfBall.drawBall(gfx);
}
private void fillList() {
int bWidth = getWidth();
int bHeight = getHeight();
int size = Math.min(bWidth, bHeight);
size -= Math.max(bfNumRow, bfNumCol) * brickGap;
size = size / (Math.max(bfNumRow, bfNumCol) + bfEmptyRow);
// add more margin
Shape.setSize(size);
if (bfBall == null) {
bfBall = new MovingBall(size, bWidth, bHeight);
} else {
bfBall.reset();
}
for (int rowCnt = 0; rowCnt < bfNumRow; rowCnt++) {
int xloc = bWidth / 2 - (bfNumRow / 2 - rowCnt) * (size + brickGap);
for (int colCnt = 0; colCnt < bfNumCol; colCnt++) {
double rand = Math.random();
Float cR = new Float(Math.random());
Float cG = new Float(Math.random());
Float cB = new Float(Math.random());
Color bc = new Color(cR.floatValue(), cG = cG.floatValue(), cB.floatValue());
int yloc = bHeight / 2 - (bfNumCol / 2 - colCnt) * (size + brickGap);
if (rand > .5) {
Circle cb = new Circle(xloc, yloc, bc);
bfList.add(cb);
} else {
Square sb = new Square(xloc, yloc, bc);
bfList.add(sb);
}
}
}
}
LinkedList<Shape> bfList;
MovingBall bfBall;
static private final Color bfBackground = Color.white;
static private final int bfNumRow = 6;
static private final int bfNumCol = 6;
static private final int bfEmptyRow = 4;
static private final int brickGap = 4;
}
Vector2D.java
/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package collisiondetection;
/**
*
* @author PC
*/
public class Vector2D {
public Vector2D(double x, double y, boolean u)
{
xVal = x;
yVal = y;
unit = u;
if(unit)
{
makeUnit();
}
}
public void add(Vector2D vec)
{
xVal += vec.xVal;
yVal += vec.yVal;
if(unit)
{
makeUnit();
}
}
public double getX()
{
return xVal;
}
public double getY()
{
return yVal;
}
public void reflect(Vector2D nor)
{
if((unit == false) || (nor.unit == false))
{
System.out.println("ERROR, not unit vector");
}
double ip = innerProduct(nor);
xVal += -2 * ip * nor.xVal;
yVal += -2 * ip * nor.yVal;
makeUnit();
}
private double innerProduct(Vector2D vec)
{
return (xVal * vec.xVal + yVal * vec.yVal);
}
private void makeUnit()
{
double mag = xVal * xVal + yVal * yVal;
if(mag == 0)
{
System.out.println("ERROR, zero vector");
}
else
{
mag = Math.sqrt(mag);
xVal /= mag;
yVal /= mag;
}
}
private double xVal;
private double yVal;
private boolean unit;
}
移动球.java
/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package collisiondetection;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
/**
*
* @author PC
*/
public class MovingBall {
public MovingBall(int sz, int bw, int bh)
{
mbSize = sz;
bWidth = bw;
bHeight = bh;
reset();
}
public Rectangle getRect()
{
return (new Rectangle((int) Math.round(mbLoc.getX() - mbSize/2), (int) Math.round(mbLoc.getY() - mbSize/2), mbSize, mbSize));
}
public void reset()
{
mbLoc = new Vector2D(mbSize, mbSize, false);
mbVel = new Vector2D(Math.random() + .1, Math.random() + .1, true);
}
public double getX()
{
return mbLoc.getX();
}
public double getY()
{
return mbLoc.getY();
}
public int getSize()
{
return mbSize;
}
public void reflect(Vector2D nor)
{
mbVel.reflect(nor);
}
public void move()
{
mbLoc.add(mbVel);
// hit a wall?
if(mbLoc.getX() >= (bWidth - mbSize/2))
{
// hit right wall
Vector2D nor = new Vector2D(-1, 0, true);
reflect(nor);
}
if(mbLoc.getY() >= (bHeight - mbSize/2))
{
Vector2D nor = new Vector2D(0, -1, true);
reflect(nor);
}
}
public void drawBall(Graphics gfx)
{
int x = (int) Math.round(mbLoc.getX() - mbSize/2);
int y = (int) Math.round(mbLoc.getY() - mbSize/2);
gfx.setColor(bColor);
gfx.fillOval(x, y, mbSize, mbSize);
}
private Vector2D mbLoc;
private Vector2D mbVel;
private int mbSize;
private Color bColor = Color.black;
int bWidth;
int bHeight;
}
形状.java
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package collisiondetection;
import java.awt.Color;
import java.awt.Graphics;
/**
*
* @author PC
*/
abstract public class Shape {
public Shape(int x, int y, Color c)
{
s_X = x;
s_Y = y;
s_Color = c;
}
public static void setSize(int sz)
{
s_Size = sz;
}
abstract public boolean collide(MovingBall ball);
abstract public void drawShape(Graphics gfx);
protected int s_X;
protected int s_Y;
protected Color s_Color;
protected static int s_Size;
}
Square.java
/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package collisiondetection;
import static collisiondetection.Shape.s_Size;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
/**
*
* @author PC
*/
public class Square extends Shape {
public Square(int x, int y, Color c)
{
super(x, y, c);
}
public boolean collide(MovingBall ball)
{
Rectangle r1 = new Rectangle(s_X - s_Size / 2, s_Y - s_Size, s_Size, s_Size);
Rectangle r2 = ball.getRect();
Rectangle r3 = r1.intersection(r2);
if (r3.isEmpty())
{
// no collision
// note thatr3 is not null
return false;
}
if (r3.getWidth() < r3.getHeight())
{
// hit horizontally
if (ball.getX() < s_X) {
// hit the left side
Vector2D nor = new Vector2D(-1, 0, true);
ball.reflect(nor);
} else {
Vector2D nor = new Vector2D(1, 0, true);
ball.reflect(nor);
}
} else {
if (ball.getY() < s_Y) {
// hit the top
Vector2D nor = new Vector2D(0, -1, true);
ball.reflect(nor);
} else {
Vector2D nor = new Vector2D(0, 1, true);
ball.reflect(nor);
}
}
return true;
}
public void drawShape(Graphics gfx)
{
gfx.setColor(s_Color);
gfx.fillRect(s_X - s_Size/2, s_Y - s_Size/2, s_Size, s_Size);
}
}
Circle.java
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package collisiondetection;
import java.awt.Color;
import java.awt.Graphics;
/**
*
* @author PC
*/
public class Circle extends Shape{
public Circle(int x, int y, Color c)
{
super(x, y, c);
}
public boolean collide(MovingBall ball)
{
double deltaX = ball.getX() - s_X;
double deltaY = ball.getY() - s_Y;
double centerDistance = Math.sqrt(deltaX * deltaX + deltaY * deltaY);
if(centerDistance * 2 > s_Size + ball.getSize())
{
// no collision
// size is the diameter, not radius
return false;
}
Vector2D nor = new Vector2D(deltaX, deltaY, true);
ball.reflect(nor);
return true;
}
public void drawShape(Graphics gfx)
{
gfx.setColor(s_Color);
gfx.fillOval(s_X - s_Size/2, s_Y - s_Size/2, s_Size, s_Size);
}
}