使用ActionListener在NewJFrame中出错

Question

我对Java完全陌生，并且正在学习如何编写基于教授的讲座视频来检测碰撞并对碰撞做出反应的程序。 这是视频的链接 。

我所有的代码都应该与他的演讲类似。 我的错误似乎在NewJFrame.java文件中。 为什么ActionListener不起作用？ 先谢谢您的帮助。

/*
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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                   
}

下划线标有“ new ActionListener（）{”，并且收到一条错误消息：

线程“主”中的异常java.lang.RuntimeException：无法编译的源代码-不是抽象的，并且不会覆盖冲突检测中的java.awt.event.ActionListener中的抽象方法actionPerformed（java.awt.event.ActionEvent）。NewJFrame。（NewJFrame .java：28）在碰撞检测.Main.main（Main.java:20）

NewJFrame.java:28引用上面的代码中“ njTimer = new Timer（1，）”这一行。

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

这是我的代码，供其他.java文件参考。

主文件：

/*
 * 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;

/**
 *
 * @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：

/*
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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.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;
}

MovingBall.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;
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;

}

Shape.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

/*
 * 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 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);
    }
}

Cirlce.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;

/**
 *
 * @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);
    }


}

Answer 1

您正在导入错误的ActionEvent。

import javafx.event.ActionEvent;

应该

import java.awt.event.ActionEvent;

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