【转】画图java源代码，只画直线，矩形，椭圆

/*
*只画直线，矩形，椭圆，只能向右下角画
*
*PainterPanel extends JPanel implements MouseListener
*addMouseListener(this);
*
*JToggleButton
*
*hxz*/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
class PainterPanel extends JPanel implements MouseListener{
    int shape=-1; //图案类型
    Point[] point=new Point[2]; //记录鼠标拖动的起始点和终点
    
    public PainterPanel(){
           super(); //调用父类构造函数 
           this.setBackground(Color.white); //设置背景颜色
        point[0]=new Point(-1,-1); //初始化变量
        point[1]=new Point(-1,-1);
           addMouseListener(this); //增加鼠标事件
    }
    
    public void mouseReleased(MouseEvent e){ //鼠标释放事件
           point[1]=new Point(e.getX(),e.getY()); //设置终点位置
           repaint(); //重绘屏幕
    }
    
    public void mouseEntered(MouseEvent e){}
    public void mouseExited(MouseEvent e){}
    public void mouseClicked(MouseEvent e){}
    
    public void mousePressed(MouseEvent e){ //鼠标按下时事件
           point[0]=new Point(e.getX(),e.getY()); //设置起始点位置
    }
      
    public void paint(Graphics g){ 
           super.paint(g);
           switch (shape){ //根据shape值绘制图形
            case 0:
             g.drawLine(point[0].x,point[0].y,point[1].x,point[1].y); //绘线
             break;
             
            case 1:
             int width=point[1].x-point[0].x;
             int height=point[1].y-point[0].y;
             g.drawOval(point[0].x,point[0].y,width,height); //绘椭圆
             break;
             
            case 2:
             width=point[1].x-point[0].x;
             height=point[1].y-point[0].y;
             g.drawRect(point[0].x,point[0].y,width,height); //绘矩形
             break; 
           } 
    }
    public void drawShape(int shape){
           this.shape=shape; 
    }
}
/*
*JToggleButton
*
*JToolBar
*
*hxz*/
public class PainterDemo extends JFrame{
    JToggleButton[] button=new JToggleButton[3]; //按钮组
    PainterPanel painter=new PainterPanel(); //绘图面板
    public PainterDemo(){
           super("Java画图程序"); //调用父类构造函数
           String[] buttonName={"直线","椭圆","矩形"}; //按钮文字
           DrawShapeListener buttonListener=new DrawShapeListener(); //按钮事件
           JToolBar toolBar=new JToolBar(); //实例化工具栏
           ButtonGroup buttonGroup=new ButtonGroup(); //实例化按钮组
           
           for (int i=0;i<button.length;i++){
                   button[i]=new JToggleButton(buttonName[i]); //实例化按钮
                   button[i].addActionListener(buttonListener); //增加按钮事件处理
                   buttonGroup.add(button[i]); //增加按钮到按钮组
                   toolBar.add(button[i]); //增加按钮到工具栏
           }
           
           Container container=getContentPane(); //得到窗口容器
           container.add(toolBar,BorderLayout.NORTH); //增加组件到容器上
           container.add(painter,BorderLayout.CENTER);  
           setSize(300,200); //设置窗口尺寸
           setVisible(true); //设置窗口为可视
           setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //关闭窗口时退出程序 
    }
//内部类
    class DrawShapeListener implements ActionListener{ //按钮事件处理
           public void actionPerformed(ActionEvent e){
            for (int i=0;i<button.length;i++){ 
                 if (e.getSource()==button[i]){ //判断来自于哪个按钮
                      painter.drawShape(i); //绘制图形
                 }    
            }   
           }
    }
   
    public static void main(String[] args){
           new PainterDemo();
    }
}