Java开发画板

public class Test {  
        public static void main(String[] args){  
            DrawBoard db = new DrawBoard();  
            db.initFrame();  
        }   
}  

public class DrawBoard extends JFrame {  
    Graphics2D g;  

    public void initFrame(){  
            //设置窗体大小，直接关闭，居中，标题  
            this.setSize(800,600);  
            this.setDefaultCloseOperation(3);  
            this.setLocationRelativeTo(null);  
            this.setTitle("画板");  
            //边框布局  
            this.setLayout(new BorderLayout());  
            PanelLeft panelLeft = new PanelLeft(g);//添加面板  
            PanelCenter panelCenter = new PanelCenter();  
            PanelDown panelDown= new PanelDown(g,panelLeft);  
            this.add(panelLeft,BorderLayout.WEST);  
            this.add(panelCenter,BorderLayout.CENTER);  
            this.add(panelDown,BorderLayout.SOUTH);  
            panelLeft.click();//调用面板方法  
            panelDown.clickColor();  
            //画板可见  
            this.setVisible(true);  
            g =(Graphics2D) panelCenter.getGraphics();//中间面板取画笔并强制转子类  
            panelLeft.g = g;//画笔传递  
            panelDown.g = g;  
            DrawListener mouse = new DrawListener(g,panelLeft);//添加鼠标监听器  
            panelCenter.addMouseListener(mouse);  
            panelCenter.addMouseMotionListener(mouse);    
        }         
}  

public class PanelLeft extends JPanel {  
    String actionCommand = "6";  
    int n;  
    public Graphics2D g;  
    Color color = Color.black;  
    public PanelLeft(Graphics2D g){  
        this.g = g;  
        setPreferredSize(new Dimension(70,0));  
    }  
    public void click(){  
        //给按钮添加监听器  
        ActionListener actionListener = new ActionListener(){  
            public void actionPerformed(ActionEvent e) {  
                actionCommand = e.getActionCommand();  
                n=0;  
                if("2".equals(actionCommand)){  
                    g.setColor(Color.white);  
                    g.setStroke(new BasicStroke(20));//设置橡皮粗细和颜色  
                }  
                else if("7".equals(actionCommand)){  
                    g.setColor(color);  
                    g.setStroke(new BasicStroke(20)); //设置刷子粗细和颜色  
                }  
                else{  
                    g.setColor(color);  
                    g.setStroke(new BasicStroke(1));//初始化画笔粗细和颜色  
                }  
             }    
        };  
        //添加按钮  
        for(int i = 0;i < 16;i++){  
            JButton button = new JButton();  
            ImageIcon image1 = new ImageIcon("images/draw"+i+".jpg");  
            ImageIcon image2 = new ImageIcon("images/draw"+i+"-1.jpg");  
            ImageIcon image3 = new ImageIcon("images/draw"+i+"-2.jpg");  
            ImageIcon image4 = new ImageIcon("images/draw"+i+"-3.jpg");  
            button.setIcon(image1);//给按钮添加图标  
            button.setRolloverIcon(image2);  
            button.setPressedIcon(image3);  
            button.setSelectedIcon(image4);  
            button.setPreferredSize(new Dimension(25,25));  
            this.add(button);  
            button.addActionListener(actionListener);//按钮添加动作监听  
            button.setActionCommand(i+"");  
        }  
    }  
}  

public class PanelDown extends JPanel {  
    Color[] colors = { Color.black, Color.gray, Color.red, Color.yellow,Color.blue };  
    Color color = Color.black;  
    Graphics2D g;  
    PanelLeft panelLeft;  
    public PanelDown(Graphics2D g,PanelLeft pl){  
            this.g = g;  
            this.panelLeft = pl;//左边面板传参  
        }  
    public void clickColor(){  
            ActionListener listener = new ActionListener() {  
                public void actionPerformed(ActionEvent e) {  
                    String actionCommandColor = e.getActionCommand();  
                    int i = Integer.valueOf(actionCommandColor);// String -> int         <span style="white-space:pre">                                  </span>//字符串型转换成整型  
                    color = colors[i];  
                    g.setColor(color);  
                    panelLeft.color = color;//把颜色传给左边面板  
                    if("2".equals(panelLeft.actionCommand)){  
                        g.setColor(Color.white);//橡皮设置白色  
                    }  
                }  
            };  
            for (int i = 0; i < colors.length; i++){  
                // 创建颜色按钮  
                JButton buttoncolor = new JButton();  
                buttoncolor.setBackground(colors[i]);  
                buttoncolor.setPreferredSize(new Dimension(25, 25));  
                buttoncolor.addActionListener(listener);//颜色按钮添加动作监听器  
                buttoncolor.setActionCommand(i + "");  
                // 面板添加颜色按钮  
                this.add(buttoncolor);  
            }  
        }  
}  

public class PanelCenter extends JPanel {  
    public PanelCenter(){  
            setBackground(Color.white);//设置背景色  
        }         
}  

public class DrawListener implements MouseMotionListener,MouseListener {  
    int x1,y1,x2,y2,a,b,xS,yS;  
    PanelLeft panelLeft;  
    Graphics2D g;  
    Random random = new Random();  
    public DrawListener(Graphics2D g,PanelLeft pl){  
        this.g = g;  
        this.panelLeft = pl;  
    }  
    public void mouseClicked(MouseEvent e) {  
            int clickCount = e.getClickCount();//记录点击次数  
            if(clickCount==1)  
            {  
            }  
            else if(clickCount==2)  
            {  
                if("13".equals(panelLeft.actionCommand)){  
                    g.drawLine(x2, y2, xS, yS);//双击自动完成多边形绘制  
                    panelLeft.n = 0;  
                }  
            }  
    }  
    public void mousePressed(MouseEvent e) {  
        x1 = e.getX();  
        y1 = e.getY();  
        if("13".equals(panelLeft.actionCommand)){  
            if(panelLeft.n != 0){  
                x1 = a;       //设置多边形中间值  
                y1 = b;  
            }  
             if(panelLeft.n == 0){  
                xS = e.getX();//记录多边形起点  
                yS = e.getY();  
            }  
        }  
    }  
    public void mouseReleased(MouseEvent e) {  
        x2 = e.getX();  
        y2 = e.getY();  
        if("10".equals(panelLeft.actionCommand)){  
            //直线  
            g.drawLine(x1, y1, x2, y2);  
        }  
        else if("12".equals(panelLeft.actionCommand)){  
            //矩形  
            g.drawRect(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2 - x1), Math.abs(y2 - y1));  
        }  
        else if("14".equals(panelLeft.actionCommand)){  
            // 椭圆  
            g.drawOval(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2 - x1), Math.abs(y2 - y1));  
        }     
        else if("13".equals(panelLeft.actionCommand)){  
            //多边形  
            g.drawLine(x1, y1, x2, y2);  
            a = x2;  
            b = y2;  
            panelLeft.n++;  
        }  
    }  
    public void mouseEntered(MouseEvent e) {  
    }  
    public void mouseExited(MouseEvent e) {  
    }  
    public void mouseDragged(MouseEvent e) {  
        if("6".equals(panelLeft.actionCommand)){  
            x2 = e.getX();  
            y2 = e.getY();  
            //绘制铅笔  
            g.drawLine(x1, y1, x2, y2);  
            x1 = x2;  
            y1 = y2;  
        }  
        else if("2".equals(panelLeft.actionCommand)){  
            x2 = e.getX();  
            y2 = e.getY();  
            //橡皮  
            g.drawLine(x1, y1, x2, y2);  
            x1 = x2;  
            y1 = y2;  
        }  
        else if ("8".equals(panelLeft.actionCommand))  
        {  
            x2 = e.getX();  
            y2 = e.getY();  
            // 喷枪  
            for (int i = 0; i < 30; i++) {  
                // 生成的随机数  
                int nextInt1 = random.nextInt(8) - 4;// [0,9]->[-5,4]  
                int nextInt2 = random.nextInt(8) - 4;// [0,9]->[-5,4]  
                // 画点  
                g.drawLine(x2 + nextInt1, y2 + nextInt2, x2+ nextInt1, y2 + nextInt2);  
            }  
        }  
        else if("7".equals(panelLeft.actionCommand)){  
            x2 = e.getX();  
            y2 = e.getY();  
            //刷子  
            g.drawLine(x1, y1, x2, y2);  
            x1 = x2;  
            y1 = y2;  
        }  
    }  
    public void mouseMoved(MouseEvent e) {  
    }  
}