如何把draw方法转换buffImage对象

class Drawing extends JPanel {
BufferedImage image;
Drawing(){
image = new BufferedImage(getWidth(),getHeight(),BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = (Graphics2D)image.getGraphics();
g2d.draw...;
} public Image getImage(){
return image;
} public void paintComponent(Graphics g){
g.drawImage(image,0,0,null);
}
}

image = new BufferedImage(getWidth(),getHeight(),BufferedImage.TYPE_INT_RGB);
抛出异常啊！
java.lang.reflect.InvocationTargetException
这是什么啊？

你可以写一个MyPanel extends JPanel
如果你想做到每个元素都可以拖拉，实际上你就应该先记录总共有哪些元素。然后在paint方法中先清空再将列表中的所有元素重画一次

嘿嘿你说的我也不懂~我是初学者！我在网上找的画板程序~想把它画出来的图形进行操作！package bagone;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Point2D;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.border.Border;public class DrawShapes extends JFrame {
    private static final long serialVersionUID = 3685715844170953607L;
    // 作图面板
    private CVS cvs;
    // 作图方式选择按钮
    private JToggleButton cycle, line, rect,arc,rgb;
    private JLabel red, blue, green;
    private ButtonGroup bgroup;
    // 按钮布局面板
    private JPanel menuPanel;
    // 复位按钮
    private JButton clean;

    private JColorChooser chooser = null;

    static Color c = new Color(0, 0, 0);    public DrawShapes() {
        super("Java");
        // this.setResizable(false);
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(640, 480);
        this.setLocationRelativeTo(null);
        this.getContentPane().add(cvs = new CVS());
        this.initComponents();
    }    // 初始化组件
    private void initComponents() {
        this.menuPanel = new JPanel(null);
        this.menuPanel.setPreferredSize(new Dimension(400, 28));
        this.menuPanel.setBorder(BorderFactory.createLineBorder(Color.gray));
        this.getContentPane().add(this.menuPanel, "South");
        this.bgroup = new ButtonGroup();
        this.cycle = new JToggleButton("圆形");
        this.cycle.setBounds(20, 4, 68, 20);
        this.line = new JToggleButton("直线");
        this.line.setBounds(100, 4, 68, 20);
        this.rect = new JToggleButton("矩形");
        this.rect.setBounds(180, 4, 68, 20);
        this.arc = new JToggleButton("扇形");
        this.arc.setBounds(260, 4, 68, 20);
        this.rgb = new JToggleButton("颜色");
        this.rgb.setBounds(340, 4, 68, 20);
        red = new JLabel();
        red.setOpaque(true);
        red.setBackground(Color.red);
        red.setBounds(258+300, 4, 20, 20);
        blue = new JLabel();
        blue.setOpaque(true);
        blue.setBackground(Color.blue);
        blue.setBounds(282+300, 4, 20, 20);
        green = new JLabel();
        green.setBackground(Color.green);
        green.setOpaque(true);
        green.setBounds(306+300, 4, 20, 20);
        this.menuPanel.add(cycle);
        this.menuPanel.add(line);
        this.menuPanel.add(rect);
        this.menuPanel.add(rgb);
        this.menuPanel.add(arc);
        this.bgroup.add(cycle);
        this.bgroup.add(line);
        this.bgroup.add(rect);
        this.bgroup.add(rgb);
        this.bgroup.add(arc);
        this.clean = new JButton("清除");
        this.clean.setBounds(420, 4, 68, 20);
        this.menuPanel.add(clean);
        // 按钮动作侦听器实例
        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
Object src = e.getSource();
if (src.equals(cycle)) {
cvs.DRAWSTATE=cvs.CYCLE;
} else if (src.equals(line)) {
cvs.DRAWSTATE=cvs.LINE;// 画直线
} else if (src.equals(rect)) {
cvs.DRAWSTATE=cvs.RECTANGLE;
// cvs.setSX(SXXX.RECTANGLE);// 画矩形
} else if (src.equals(clean)) {
cvs.reset();// 复位
} else if (src.equals(arc)) {
new SetArc();
cvs.DRAWSTATE=cvs.ARC;
} else if (src.equals(rgb)) {
Color newColor = JColorChooser.showDialog(null, "调色板", c);
c = newColor;
}
}
        };
        // 给按钮注册侦听器
        this.cycle.addActionListener(al);
        this.line.addActionListener(al);
        this.rect.addActionListener(al);
        this.clean.addActionListener(al);
        this.arc.addActionListener(al);
        this.rgb.addActionListener(al);
//        MouseListener ml = new MouseAdapter() {
//            public void mousePressed(MouseEvent e) {
//                Object s = e.getSource();
//                Border b = BorderFactory.createLoweredBevelBorder();
//                if (s.equals(red)) {
//                    red.setBorder(b);
//                    blue.setBorder(null);
//                    green.setBorder(null);
//                } else if (s.equals(blue)) {
//                    blue.setBorder(b);
//                    red.setBorder(null);
//                    green.setBorder(null);
//                } else if (s.equals(green)) {
//                    green.setBorder(b);
//                    blue.setBorder(null);
//                    red.setBorder(null);
//                }
//            }
//        };
//        blue.addMouseListener(ml);
//        red.addMouseListener(ml);
//        green.addMouseListener(ml);
    }    // 程序入口
    public static void main(String[] aregs) throws Exception {
        // 调用系统视觉设置
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new DrawShapes().setVisible(true);
            }
        });
    }
}我改来改去也改不明白~~谁能帮我看看！！就是这个程序！

// 主作图面板类,可接收一般鼠标事件和鼠标拖动事件
class CVS extends Canvas implements MouseListener, MouseMotionListener {
    private static final long serialVersionUID = 5585026114112579483L;    // 指定图形的第一点,比如矩形的角点,圆形的圆心,直线的第一点
    private int x, y;
    // 作图大小
    private int w, h;
    // 作图类型控制
    public int DRAWSTATE = 0;
    public final int CYCLE = 60, RECTANGLE = 61, LINE = 62, ARC = 63;
    // 双缓冲,背景缓冲区和临时缓冲区
    private BufferedImage background, buff;
    // 图像更新标记
    private boolean hasChanged;
    // 背景色,临时作图色,前景色
    private Color bgc = Color.white;
    public CVS() {
        this.addMouseListener(this);
        this.addMouseMotionListener(this);
    }    // 绘制临时缓冲区
    private void drawing(int X, int Y) {
        Graphics g = buff.getGraphics();
        g.setColor(bgc);
        g.clearRect(0, 0, w, h);
        copyBuffer();
        g.setColor(DrawShapes.c);
        Point p = new Point(x, y);
        Point2D p2 = new Point2D.Double(X, Y);
        int dist = (int) p.distance(p2);
        int dx = x - X;
        dx = Math.abs(dx);
        int dy = y - Y;
        dy = Math.abs(dy);
        switch (DRAWSTATE) {
        case CYCLE:
         g.fillOval(x < X ? x : X, y < Y ? y : Y, dx, dy);
            break;
        case LINE:
            g.drawLine(x, y, X, Y);
            break;
        case RECTANGLE:
            g.fillRect(x < X ? x : X, y < Y ? y : Y, dx, dy);
            break;
        case ARC:
            g.fillArc(x < X ? x : X, y < Y ? y : Y, dx, dy,SetArc.ArcA,SetArc.ArcB);
         break;
        }
        g.dispose();
        drawBufferToCVS();
    }
    // 绘制背景缓冲区
    private void drawBuffer(int X, int Y) {
        Graphics2D gd = background.createGraphics();
        gd.setColor(DrawShapes.c);
        gd.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
        Point p = new Point(x, y);
        Point2D p2 = new Point2D.Double(X, Y);
        int dist = (int) p.distance(p2);
        int dx = x - X;
        dx = Math.abs(dx);
        int dy = y - Y;
        dy = Math.abs(dy);
        switch (DRAWSTATE) {
        case CYCLE:
         //画正圆
         gd.fillOval(x < X ? x : X, y < Y ? y : Y, dx, dy);
            break;
        case LINE:
            gd.drawLine(x, y, X, Y);
            break;
        case RECTANGLE:
            gd.fillRect(x < X ? x : X, y < Y ? y : Y, dx, dy);
            break;
        case ARC:
         gd.fillArc(x < X ? x : X, y < Y ? y : Y, dx, dy,SetArc.ArcA,SetArc.ArcB);
         break;
        default:
            popupMsg();
        }
        gd.dispose();
        Graphics g = this.getGraphics();
        g.clearRect(0, 0, w, h);
        g.drawImage(background, 0, 0, null);
        g.dispose();
    }    private void popupMsg() {
        JOptionPane.showMessageDialog(this, "请选择一种作图方式开始作图.");
    }    // 复制背景缓冲区内容到临时缓冲区
    private void copyBuffer() {
        Graphics g = buff.getGraphics();
        g.drawImage(background, 0, 0, null);
        g.dispose();
    }    // 印出临时缓冲区内容到窗口
    private void drawBufferToCVS() {
        Graphics g = this.getGraphics();
        g.drawImage(buff, 0, 0, null);
        System.out.println(" buff : " + buff.getWidth()+" " + buff.getHeight());
        g.dispose();
    }    // 清除双缓冲区并清除窗口内容
    public void reset() {
        clearContents(buff);
        clearContents(background);
        Graphics g = this.getGraphics();
        g.setColor(bgc);
        g.fillRect(0, 0, w, h);
        g.dispose();
    }    // 清除指定缓冲区内容
    private void clearContents(BufferedImage i) {
        Graphics g = i.getGraphics();
        g.setColor(bgc);
        g.fillRect(0, 0, w, h);
        g.dispose();
    }    // 初始化缓冲区
    private void initImages() {
        background = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        buff = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        clearContents(background);
        clearContents(buff);
    }    // 重写此方法,以便在窗口重新显示时能正确显示最后的内容.
    public void paint(Graphics g) {
        if (background == null) {
            w = this.getToolkit().getScreenSize().width;
            h = this.getToolkit().getScreenSize().height;
            initImages();
        }
        g.drawImage(background, 0, 0, null);
        g.dispose();
    }    // 双击作图区也能做清除动作,呵呵
    public void mouseClicked(MouseEvent e) {
        if (e.getClickCount() == 2)
            reset();
    }    public void mouseEntered(MouseEvent e) {
    }    public void mouseExited(MouseEvent e) {
    }    // 每当按下鼠标时就重新设置第一点的坐标
    public void mousePressed(MouseEvent e) {
        this.x = e.getX();
        this.y = e.getY();
    }    // 每当释放鼠标时就决定是否需要将背景缓冲区印出到窗口
    public void mouseReleased(MouseEvent e) {
        if (hasChanged) {
            hasChanged = false;
            drawBuffer(e.getX(), e.getY());
        }
    }    // 每当鼠标拖动时开始作图
    public void mouseDragged(MouseEvent e) {
        hasChanged = true;
        drawing(e.getX(), e.getY());
    }    public void mouseMoved(MouseEvent e) {
    }
}

调试易

如何把draw方法转换buffImage对象

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