/*

*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[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

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();

}

}