用applet响应鼠标在applet里面画线 100分求代码

解决方法:
在Applet上add一个canvas,然后在canvas上画线.
可以新建一个extends Canvas 类的class,重构paint方法,在paint方法里面实现画直线方法和过程.
当鼠标拉动的时候,要把先前画的直线擦掉,把新的直线画上去.
一下是一个示范代码(我同学写的):
package HelloWorld;import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.awt.geom.*;
import java.util.Vector;
/**
* Title: 
* Description: 
* Copyright: Copyright (c) 2003
* Company: 
* @author unascribed
* @version 1.0
*/public class TLine extends JFrame { TLinesCanvas canvas;
 public TLine()
 {
 Container container=getContentPane();
 canvas=new TLinesCanvas();
 container.add(canvas);
 pack();
 show();
 } public static void main(String args[])
 {
 new TLine();
 } class TLinesCanvas extends Canvas
 {
 Vector Lines=new Vector();
 Line2D currentLine;
 Point2D start=new Point2D.Float();
 Point2D pretempend=new Point2D.Float();
 Point2D tempend=new Point2D.Float();
 Point2D end=new Point2D.Float();
 boolean isEnd;
 public TLinesCanvas()
 {
 setBackground(Color.white);
 setSize(400,250);
 addMouseListener(new LinesListener());
 addMouseMotionListener(new LineMouseMotionListener());
 } public void paint(Graphics g)
 {
 Graphics2D g2D=(Graphics2D)g;
 if(isEnd==false)
 {
 g2D.drawLine((int)start.getX(),(int)start.getY(),(int)tempend.getX(),(int)tempend.getY());
 }
 else
 {
 g2D.drawLine((int)start.getX(),(int)start.getY(),(int)end.getX(),(int)end.getY());
 } for(int i=0;i<Lines.size();i++)
 {
 Line2D iLine=(Line2D)Lines.elementAt(i);
 g2D.drawLine((int)iLine.getX1(),(int)iLine.getY1(),(int)iLine.getX2(),(int)iLine.getY2());
 }
 } class LinesListener extends MouseAdapter
 {
 public void mousePressed(MouseEvent e)
 {
 start.setLocation(e.getPoint());
 isEnd=false;
 } public void mouseReleased(MouseEvent e)
 {
 end.setLocation(e.getPoint());
 isEnd=true;
 currentLine=new Line2D.Float(start,end);
 Lines.addElement(currentLine);
 repaint();
 }
 } class LineMouseMotionListener implements MouseMotionListener
 {
 public void mouseDragged(MouseEvent e)
 {
 tempend.setLocation(e.getPoint());
 repaint();
 } public void mouseMoved(MouseEvent e)
 {
 }
 }
 }
}
程序存在的问题:画直线过程中,canvas会闪烁.原因是:每次拉动鼠标时,Vector对象把所有直线重画一次.
至今还没能解决问题.

解决方案 »

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已测试
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class appletDrawLine extends Applet{
boolean isMouseDown=false;
int x1=0;
int y1=0;
int x2=0;
int y2=0;
public void init(){
setLayout(new BorderLayout());
addMouseListener(new DisposalMouse());
addMouseMotionListener(new DisposalMouseMotion());
setSize(300,300);
setVisible(true);
}
public void paint(Graphics g){
        g.drawLine(x1,y1,x2,y2);
}
//用来处理鼠标事件
class DisposalMouse extends MouseAdapter{
     public void mousePressed(MouseEvent e){
     isMouseDown=true;
     x1=e.getX();
     y1=e.getY();
     }
     public void mouseReleased(MouseEvent e){
    isMouseDown=false;
     }    }
    class DisposalMouseMotion extends MouseMotionAdapter{
     public void mouseDragged(MouseEvent e){
     if(isMouseDown==true){
        x2=e.getX();
     y2=e.getY();
     repaint();
    }
    }
    }
}
<HTML>
<APPLET CODE="appletDrawLine.class" WIDTH="300" HEIGHT="300">
</APPLET>
</HTML>
在html里面
却说找不到class
我已经放在一个目录下面了
<HTML>
<HEAD>
<META NAME="GENERATOR" Content="Microsoft Visual Studio 6.0">
</HEAD>
<BODY> 

<applet
code=Applet1.class
name=Applet1
width=320
height=200 VIEWASTEXT>
<param name=label value="This string was passed from the HTML host.">
<param name=background value="008080">
<param name=foreground value="FFFFFF">
</applet></BODY>
</HTML>
测试过了，
在同一目录下，
如果你装了VJ++6.0，就没有问题。