如何用Java编写一个绘制图形的小程序？

import java.awt.*

import java.awt.event.*

import java.awt.geom.*

import javax.swing.*

//不规则图形的绘制

public class IrregularShapeDemo extends JFrame {

GeneralPath gPath= new GeneralPath()//GeneralPath对象实例

Point aPoint

//构造函数

public IrregularShapeDemo() {

super("不规则图形的绘制")//调用父类构造函数

enableEvents(AWTEvent.MOUSE_EVENT_MASK|AWTEvent.MOUSE_MOTION_EVENT_MASK)//允许事件

setSize(300, 200)//设置窗口尺寸

setVisible(true)//设置窗口可视

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)//关闭窗口时退出程序

}

public void paint(Graphics g) { //重载窗口组件的paint()方法

Graphics2D g2D = (Graphics2D)g//获取图形环境

g2D.draw(gPath)//绘制路径

}

public static void main(String[] args) {

new IrregularShapeDemo()

}

protected void processMouseEvent(MouseEvent e) { //鼠标事件处理

if(e.getID() == MouseEvent.MOUSE_PRESSED) {

aPoint = e.getPoint()//得到当前鼠标点

gPath = new GeneralPath()//重新实例化GeneralPath对象

gPath.moveTo(aPoint.x,aPoint.y)//设置路径点

}

}

protected void processMouseMotionEvent(MouseEvent e) { //鼠标运动事件处理

if(e.getID() == MouseEvent.MOUSE_DRAGGED) {

aPoint = e.getPoint()//得到当前鼠标点

gPath.lineTo(aPoint.x, aPoint.y)//设置路径

gPath.moveTo(aPoint.x, aPoint.y)

repaint()//重绘组件

}

}

}

import java.awt.*

import java.awt.event.*

import java.util.*

import javax.swing.*

class MyLine

{

private int x1,x2,y1,y2

public MyLine(int x1,int x2,int y1,int y2)

{

this.x1=x1

this.x2=x2

this.y1=y1

this.y2=y2

}

public void drawMe(Graphics g)

{

g.drawLine(x1,y1,x2,y2)

g.drawString("起始坐标："+new String(x1+","+y1),x1,y1)

}

}

public class DrawLine extends Frame

{

Vector v=new Vector()

public static void main(String[]args)

{

DrawLine dl=new DrawLine()

dl.init()

}

public void paint(Graphics g)

{

g.setColor(Color.BLUE)

Enumeration en=v.elements()

while(en.hasMoreElements())

{

MyLine m=(MyLine)en.nextElement()

m.drawMe(g)

}

}

public void init()

{

setSize(300,300)

setVisible(true)

addMouseListener(new MouseAdapter()

{

int x1,x2,y1,y2

public void mousePressed(MouseEvent e)

{

x1=e.getX()

y1=e.getY()

}

public void mouseReleased(MouseEvent e)

{

x2=e.getX()

y2=e.getY()

Graphics g=e.getComponent().getGraphics()

g.setColor(Color.BLUE)

g.drawLine(x1,y1,x2,y2)

g.drawString(new String("起始点坐标："+x1+","+y1),x1,y1)

v.add(new MyLine(x1,x2,y1,y2))// here pay attention

}

})

addWindowListener(new WindowAdapter()

{

public void windowClosing(WindowEvent e)

{

((Window)e.getSource()).dispose()

System.exit(0)

}}

)

}

}

Applet小程序是需要嵌入在网页中执行的，如果你不想用html，那么要加入

public void init() {}方法，在里边初始化容器和组件，那么在调用paint的时候就能看到效果了。

public class DrawLine extends Applet implements ActionListener {

Button btn

public void init() {

btn = new Button("确定")

add(btn)

btn.addActionListener(this)

}

public void paint(Graphics g) {

g.drawLine(0, 0, 500, 500)

}

public void actionPerformed(ActionEvent e) {

if (e.getSource() == btn) {

repaint()

}

}

}

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