Question

JAVA实现简单的画图板

这个画图板只有3个选项：画直线，画正四边形，画圆

选哪个就在下面的画板上画哪个
还有一个要求就是要求每次画新的时候，旧的图还会保留在画布上
（比如先画了个直线，再画圆的时候直线不会消失）
求大虾们怎么实现这个程序，具体程序可以加分
应该不是很长的程序 还有就是最好能用applet实现 不要直接复制网上的程序。。明显跟我的要求不一样

Answer 1

楼主写一个html，很容易把下面代码嵌入到applet，可以google一下实现，
还有copy自己不知道算不算复制。。。-_-!
--------------------------------------------------------------------
楼主给你一个我的，直接保存成pb.java编译运行，就是你要的画图功能 ，可以参考一下
____________________________________________________________________

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import java.awt.geom.*;
import java.io.*;

class Point implements Serializable
{
int x,y;
Color col;
int tool;
int boarder;

Point(int x, int y, Color col, int tool, int boarder)
{
this.x = x;
this.y = y;
this.col = col;
this.tool = tool;
this.boarder = boarder;
}
}

class paintboard extends Frame implements ActionListener,MouseMotionListener,MouseListener,ItemListener
{
int x = -1, y = -1;
int con = 1;//画笔大小
int Econ = 5;//橡皮大小

int toolFlag = 0;//toolFlag:工具标记
//toolFlag工具对应表：
//（0--画笔）；（1--橡皮）；（2--清除）；
//（3--直线）；（4--圆）；（5--矩形）；

Color c = new Color(0,0,0); //画笔颜色
BasicStroke size = new BasicStroke(con,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);//画笔粗细
Point cutflag = new Point(-1, -1, c, 6, con);//截断标志

Vector paintInfo = null;//点信息向量组
int n = 1;

FileInputStream picIn = null;
FileOutputStream picOut = null;

ObjectInputStream VIn = null;
ObjectOutputStream VOut = null;

// *工具面板--画笔，直线，圆，矩形，多边形,橡皮，清除*/
Panel toolPanel;
Button eraser, drLine,drCircle,drRect;
Button clear ,pen;
Choice ColChoice,SizeChoice,EraserChoice;
Button colchooser;
Label 颜色,大小B,大小E;
//保存功能
Button openPic,savePic;
FileDialog openPicture,savePicture;

paintboard(String s)
{
super(s);
addMouseMotionListener(this);
addMouseListener(this);

paintInfo = new Vector();

/*各工具按钮及选择项*/
//颜色选择
ColChoice = new Choice();
ColChoice.add("black");
ColChoice.add("red");
ColChoice.add("blue");
ColChoice.add("green");
ColChoice.addItemListener(this);
//画笔大小选择
SizeChoice = new Choice();
SizeChoice.add("1");
SizeChoice.add("3");
SizeChoice.add("5");
SizeChoice.add("7");
SizeChoice.add("9");
SizeChoice.addItemListener(this);
//橡皮大小选择
EraserChoice = new Choice();
EraserChoice.add("5");
EraserChoice.add("9");
EraserChoice.add("13");
EraserChoice.add("17");
EraserChoice.addItemListener(this);
////////////////////////////////////////////////////
toolPanel = new Panel();

clear = new Button("清除");
eraser = new Button("橡皮");
pen = new Button("画笔");
drLine = new Button("画直线");
drCircle = new Button("画圆形");
drRect = new Button("画矩形");

openPic = new Button("打开图画");
savePic = new Button("保存图画");

colchooser = new Button("显示调色板");

//各组件事件监听
clear.addActionListener(this);
eraser.addActionListener(this);
pen.addActionListener(this);
drLine.addActionListener(this);
drCircle.addActionListener(this);
drRect.addActionListener(this);
openPic.addActionListener(this);
savePic.addActionListener(this);
colchooser.addActionListener(this);

颜色 = new Label("画笔颜色",Label.CENTER);
大小B = new Label("画笔大小",Label.CENTER);
大小E = new Label("橡皮大小",Label.CENTER);
//面板添加组件
toolPanel.add(openPic);
toolPanel.add(savePic);

toolPanel.add(pen);
toolPanel.add(drLine);
toolPanel.add(drCircle);
toolPanel.add(drRect);

toolPanel.add(颜色); toolPanel.add(ColChoice);
toolPanel.add(大小B); toolPanel.add(SizeChoice);
toolPanel.add(colchooser);

toolPanel.add(eraser);
toolPanel.add(大小E); toolPanel.add(EraserChoice);

toolPanel.add(clear);
//工具面板到APPLET面板
add(toolPanel,BorderLayout.NORTH);

setBounds(60,60,900,600); setVisible(true);
validate();
//dialog for save and load

openPicture = new FileDialog(this,"打开图画",FileDialog.LOAD);
openPicture.setVisible(false);
savePicture = new FileDialog(this,"保存图画",FileDialog.SAVE);
savePicture.setVisible(false);

openPicture.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{ openPicture.setVisible(false); }
});

savePicture.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{ savePicture.setVisible(false); }
});

addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{ System.exit(0);}
});

}

public void paint(Graphics g)
{
Graphics2D g2d = (Graphics2D)g;

Point p1,p2;

n = paintInfo.size();

if(toolFlag==2)
g.clearRect(0,0,getSize().width,getSize().height);//清除

for(int i=0; i<n ;i++){
p1 = (Point)paintInfo.elementAt(i);
p2 = (Point)paintInfo.elementAt(i+1);
size = new BasicStroke(p1.boarder,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);

g2d.setColor(p1.col);
g2d.setStroke(size);

if(p1.tool==p2.tool)
{
switch(p1.tool)
{
case 0://画笔

Line2D line1 = new Line2D.Double(p1.x, p1.y, p2.x, p2.y);
g2d.draw(line1);
break;

case 1://橡皮
g.clearRect(p1.x, p1.y, p1.boarder, p1.boarder);
break;

case 3://画直线
Line2D line2 = new Line2D.Double(p1.x, p1.y, p2.x, p2.y);
g2d.draw(line2);
break;

case 4://画圆
Ellipse2D ellipse = new Ellipse2D.Double(p1.x, p1.y, Math.abs(p2.x-p1.x) , Math.abs(p2.y-p1.y));
g2d.draw(ellipse);
break;

case 5://画矩形
Rectangle2D rect = new Rectangle2D.Double(p1.x, p1.y, Math.abs(p2.x-p1.x) , Math.abs(p2.y-p1.y));
g2d.draw(rect);
break;

case 6://截断，跳过
i=i+1;
break;

default :
}//end switch
}//end if
}//end for
}

public void itemStateChanged(ItemEvent e)
{
if(e.getSource()==ColChoice)//预选颜色
{
String name = ColChoice.getSelectedItem();

if(name=="black")
{c = new Color(0,0,0); }
else if(name=="red")
{c = new Color(255,0,0);}
else if(name=="green")
{c = new Color(0,255,0);}
else if(name=="blue")
{c = new Color(0,0,255);}
}
else if(e.getSource()==SizeChoice)//画笔大小
{
String selected = SizeChoice.getSelectedItem();

if(selected=="1")
{
con = 1;
size = new BasicStroke(con,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);

}
else if(selected=="3")
{
con = 3;
size = new BasicStroke(con,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);

}
else if(selected=="5")
{con = 5;
size = new BasicStroke(con,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);

}
else if(selected=="7")
{con = 7;
size = new BasicStroke(con,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);

}
else if(selected=="9")
{con = 9;
size = new BasicStroke(con,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);

}
}
else if(e.getSource()==EraserChoice)//橡皮大小
{
String Esize = EraserChoice.getSelectedItem();

if(Esize=="5")
{ Econ = 5*2; }
else if(Esize=="9")
{ Econ = 9*2; }
else if(Esize=="13")
{ Econ = 13*2; }
else if(Esize=="17")
{ Econ = 17*3; }

}

}

public void mouseDragged(MouseEvent e)
{
Point p1 ;
switch(toolFlag){
case 0://画笔
x = (int)e.getX();
y = (int)e.getY();
p1 = new Point(x, y, c, toolFlag, con);
paintInfo.addElement(p1);
repaint();
break;

case 1://橡皮
x = (int)e.getX();
y = (int)e.getY();
p1 = new Point(x, y, null, toolFlag, Econ);
paintInfo.addElement(p1);
repaint();
break;

default :
}
}

public void mouseMoved(MouseEvent e) {}

public void update(Graphics g)
{
paint(g);
}

public void mousePressed(MouseEvent e)
{
Point p2;
switch(toolFlag){
case 3://直线
x = (int)e.getX();
y = (int)e.getY();
p2 = new Point(x, y, c, toolFlag, con);
paintInfo.addElement(p2);
break;

case 4: //圆
x = (int)e.getX();
y = (int)e.getY();
p2 = new Point(x, y, c, toolFlag, con);
paintInfo.addElement(p2);
break;

case 5: //矩形
x = (int)e.getX();
y = (int)e.getY();
p2 = new Point(x, y, c, toolFlag, con);
paintInfo.addElement(p2);
break;

default :
}
}

public void mouseReleased(MouseEvent e)
{
Point p3;
switch(toolFlag){
case 0://画笔
paintInfo.addElement(cutflag);
break;

case 1: //eraser
paintInfo.addElement(cutflag);
break;

case 3://直线
x = (int)e.getX();
y = (int)e.getY();
p3 = new Point(x, y, c, toolFlag, con);
paintInfo.addElement(p3);
paintInfo.addElement(cutflag);
repaint();
break;

case 4: //圆
x = (int)e.getX();
y = (int)e.getY();
p3 = new Point(x, y, c, toolFlag, con);
paintInfo.addElement(p3);
paintInfo.addElement(cutflag);
repaint();
break;

case 5: //矩形
x = (int)e.getX();
y = (int)e.getY();
p3 = new Point(x, y, c, toolFlag, con);
paintInfo.addElement(p3);
paintInfo.addElement(cutflag);
repaint();
break;

default:
}
}

public void mouseEntered(MouseEvent e){}

public void mouseExited(MouseEvent e){}

public void mouseClicked(MouseEvent e){}

public void actionPerformed(ActionEvent e)
{

if(e.getSource()==pen)//画笔
{toolFlag = 0;}

if(e.getSource()==eraser)//橡皮
{toolFlag = 1;}

if(e.getSource()==clear)//清除
{
toolFlag = 2;
paintInfo.removeAllElements();
repaint();
}

if(e.getSource()==drLine)//画线
{toolFlag = 3;}

if(e.getSource()==drCircle)//画圆
{toolFlag = 4;}

if(e.getSource()==drRect)//画矩形
{toolFlag = 5;}

if(e.getSource()==colchooser)//调色板
{
Color newColor = JColorChooser.showDialog(this,"调色板",c);
c = newColor;
}

if(e.getSource()==openPic)//打开图画
{

openPicture.setVisible(true);

if(openPicture.getFile()!=null)
{
int tempflag;
tempflag = toolFlag;
toolFlag = 2 ;
repaint();

try{
paintInfo.removeAllElements();
File filein = new File(openPicture.getDirectory(),openPicture.getFile());
picIn = new FileInputStream(filein);
VIn = new ObjectInputStream(picIn);
paintInfo = (Vector)VIn.readObject();
VIn.close();
repaint();
toolFlag = tempflag;

}

catch(ClassNotFoundException IOe2)
{
repaint();
toolFlag = tempflag;
System.out.println("can not read object");
}
catch(IOException IOe)
{
repaint();
toolFlag = tempflag;
System.out.println("can not read file");
}
}

}

if(e.getSource()==savePic)//保存图画
{
savePicture.setVisible(true);
try{
File fileout = new File(savePicture.getDirectory(),savePicture.getFile());
picOut = new FileOutputStream(fileout);
VOut = new ObjectOutputStream(picOut);
VOut.writeObject(paintInfo);
VOut.close();
}
catch(IOException IOe)
{
System.out.println("can not write object");
}

}
}
}//end paintboard

public class pb
{
public static void main(String args[])
{ new paintboard("画图程序"); }
}

Answer 2

这个程序多画了两个图形，但你要的都在上面，要求保留图形是和“repaint()”有关
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class DrawGraphicsDemo extends Applet implements ActionListener{
int flag=0;
Panel p=new Panel();
Button line=new Button("划线");
Button oval=new Button("画圈");
Button rect=new Button("画矩形");
Button polygon=new Button("画多边形");
Button arc=new Button("画扇形");
int xPoints[]={50,60,90,120,150
};
int yPoints[]={130,40,95,120,50
};
public void init(){
p.add(line);p.add(arc);
p.add(rect);p.add(polygon);
p.add(oval);

line.addActionListener(this);
rect.addActionListener(this);
arc.addActionListener(this);
polygon.addActionListener(this);
oval.addActionListener(this);

this.add(p);
p.setVisible(true);
}

public void actionPerformed(ActionEvent e){
if(e.getSource()==line) flag=1;
if(e.getSource()==oval) flag=2;
if(e.getSource()==rect) flag=3;
if(e.getSource()==polygon) flag=4;
if(e.getSource()==arc) flag=5;
// repaint();
}

public void paint(Graphics g){
Color c=g.getColor();
switch(flag){
case 1:g.drawLine(150,150,500,500);break;
case 2:g.drawOval(50,80,40,40);
g.setColor(Color.red);
g.fillOval(100,80,40,40);
g.drawOval(150,80,60,40);
g.setColor(c);
break;
case 3:g.drawRect(20,80,40,30);
g.fillRect(80,80,40,60);
g.drawRoundRect(150,80,80,60,20,10);
g.fillRoundRect(170,90,40,40,10,20);
g.setColor(c);
break;
case 4:g.drawPolygon(xPoints,yPoints,5);break;
case 5:g.drawArc(30,50,100,120,0,45);
g.fillArc(120,80,150,100,45,90);
}
}

}

Answer 3

package miniPad;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.geom.*;
import java.io.*;

public class MinidrawPad extends JFrame implements Serializable{

String names[]={
//"New",
//"Open",
//"Save", //这三个是基本操作按钮，包括"新建"、"打开"、"保存"

/*接下来是我们的画图板上面有的基本的几个绘图单元按钮*/

"Pencil", //铅笔画，也就是用鼠标拖动着随意绘图
"Line", //绘制直线
"Rect", //绘制空心矩形
"fRect", //绘制以指定颜色填充的实心矩形
"Oval", //绘制空心椭圆
"fOval", //绘制以指定颜色填充的实心椭圆
"Circle", //绘制圆形
"fCircle", //绘制以指定颜色填充的实心圆形
"RoundRect", //绘制空心圆角矩形
"frRect", //绘制以指定颜色填充的实心圆角矩形
"Rubber", //橡皮擦，可用来擦去已经绘制好的图案
"Color", //选择颜色按钮，可用来选择需要的颜色
"Stroke", //选择线条粗细的按钮，输入需要的数值可以实现绘图线条粗细的变化
"Word" //输入文字按钮，可以在绘图板上实现文字输入
};

String tipText[]={
//这里是鼠标移动到相应按钮上面上停留时给出的提示说明条
//读者可以参照上面的按钮定义对照着理解
// "Draw a new picture",
//"Open a saved picture",
//"Save current drawing",
"Draw at will",
"Draw a straight line",
"Draw a rectangle",
"Fill a ractangle",
"Draw an oval",
"Fill an oval",
"Draw a circle",
"Fill a circle",
"Draw a round rectangle",
"Fill a round rectangle",
"Erase at will",
"Choose current drawing color",
"Set current drawing stroke",
"Write down what u want"
};

static final int DEFAULTWIDTH=900;
static final int DEFAULTHEIGHT=500;
JMenu file,color,stroke,help;

JMenuItem neww, save,open,exit,colorChooser,strokeChooser,helpTheme;

ArrayList<JMenuItem> mitems=new ArrayList<JMenuItem>();
ArrayList<JRadioButton> drawButtons=new ArrayList<JRadioButton>();
ArrayList<ToolDraws> toolList=new ArrayList<ToolDraws>();
ButtonGroup bgroup=new ButtonGroup();
DrawPanel drawpanel;
JLabel status;

int x1,y1,x2,y2;
int currentSelect;
public MinidrawPad(){
setSize(DEFAULTWIDTH,DEFAULTHEIGHT);
setLocation(100,100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

file=new JMenu("文件");
color=new JMenu("颜色");
stroke=new JMenu("笔性");
help=new JMenu("帮助");

JMenuBar bar=new JMenuBar();
setJMenuBar(bar);

bar.add(file);
bar.add(color);
bar.add(stroke);
bar.add(help);

neww=new JMenuItem("新建(N)");
save=new JMenuItem("保存(S)");
open=new JMenuItem("打开(O)");
exit=new JMenuItem("退出(Q)");
colorChooser=new JMenuItem("颜色选择器");
strokeChooser=new JMenuItem("线条设置");
helpTheme= new JMenuItem("帮助主题");

color.add(colorChooser);
stroke.add(strokeChooser);
help.add(helpTheme);

colorChooser.addActionListener(new ItemHandler());
strokeChooser.addActionListener(new ItemHandler());
helpTheme.addActionListener(new ItemHandler());

mitems.add(neww);
mitems.add(save);
mitems.add(open);
mitems.add(exit);

char[] mo={'N','S','O','Q'};
KeyStroke[] ks={KeyStroke.getKeyStroke(KeyEvent.VK_N,InputEvent.CTRL_MASK),
KeyStroke.getKeyStroke(KeyEvent.VK_S,InputEvent.CTRL_MASK),
KeyStroke.getKeyStroke(KeyEvent.VK_0,InputEvent.CTRL_MASK),
KeyStroke.getKeyStroke(KeyEvent.VK_Q,InputEvent.CTRL_MASK)
};

for(int i=0;i<mitems.size();i++){
mitems.get(i).addActionListener(new ItemHandler());
mitems.get(i).setMnemonic(mo[i]);
mitems.get(i).setAccelerator(ks[i]);
file.add(mitems.get(i));

}

JToolBar tool =new JToolBar();
add(tool,BorderLayout.NORTH);

status =new JLabel(" 1");
add(status,BorderLayout.SOUTH);

for(int i=0;i<names.length;i++)
drawButtons.add(new JRadioButton(names[i]));

for(int i=0;i<drawButtons.size();i++){
drawButtons.get(i).addActionListener(new drawButtonHandler());
drawButtons.get(i).setToolTipText(tipText[i]);
bgroup.add(drawButtons.get(i));
tool.add(drawButtons.get(i));
}

drawpanel =new DrawPanel();
drawpanel.setBackground(Color.white);
add(drawpanel,BorderLayout.CENTER);
drawpanel.addMouseListener(new MouseMoniter());
drawpanel.addMouseMotionListener(new MouseMoniter2());

setVisible(true);

}

class MouseMoniter extends MouseAdapter{

public void mousePressed(MouseEvent e){
// x1=e.getX();
//y1=e.getY();
createObject(currentSelect);
toolList.get(toolList.size()-1).x1=e.getX();
toolList.get(toolList.size()-1).y1=e.getY();
System.out.println("press");
}

public void mouseReleased(MouseEvent e){
//x2=e.getX();
//y2=e.getY();
if(currentSelect==6||currentSelect==7)
return;
toolList.get(toolList.size()-1).x2=e.getX();
toolList.get(toolList.size()-1).y2=e.getY();

System.out.println("released");
drawpanel.repaint();

}

}

public void createObject(int currentSelect){
//生成画图工具对象
System.out.println(currentSelect);
switch(currentSelect){
case 0 :toolList.add(new Will());break;
case 1 :toolList.add(new Line());break;
case 2 :toolList.add(new Rect());break;
case 3 :toolList.add(new Rect_f());break;
case 4 :toolList.add(new Oval());break;
case 5 :toolList.add(new Oval_f());break;
case 6 :toolList.add(new Circle());break;
case 7 :toolList.add(new Circle_f());break;
case 8 :toolList.add(new Roundrect());break;
case 9 :toolList.add(new Roundrect_f());break;
case 10 :toolList.add(new Rub());break;
default : ;
}

}

class MouseMoniter2 extends MouseMotionAdapter{

public void mouseMoved(MouseEvent e){

status.setText("mouse position: [x:"+e.getX()+" y:"+e.getY()+"]");
}

public void mouseDragged(MouseEvent e){
System.out.println("dragged");
x2=e.getX();
y2=e.getY();

toolList.get(toolList.size()-1).x2=e.getX();
toolList.get(toolList.size()-1).y2=e.getY();
//特别的类 Will rub
if(currentSelect==0){
createObject(0);
toolList.get(toolList.size()-1).x1=
toolList.get(toolList.size()-2).x2;
toolList.get(toolList.size()-1).y1=
toolList.get(toolList.size()-2).y2;
toolList.get(toolList.size()-1).x2=
e.getX();
toolList.get(toolList.size()-1).y2=
e.getY();
}

if(currentSelect==10){
createObject(10);
toolList.get(toolList.size()-1).x1=e.getX();
toolList.get(toolList.size()-1).y1=e.getY();
}

if(currentSelect==6||currentSelect==7){
toolList.get(toolList.size()-1).x2=
e.getX();
toolList.get(toolList.size()-1).y2=
toolList.get(toolList.size()-1).x2-
toolList.get(toolList.size()-1).x1+
toolList.get(toolList.size()-1).y1;
}
drawpanel.repaint();
}
}

class drawButtonHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
//
int i=drawButtons.indexOf((JRadioButton)e.getSource());
currentSelect=i;

}
}

class ItemHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
//
if(e.getSource()==save){

FileDialog ff=new FileDialog(MinidrawPad.this,"保存文件",
FileDialog.SAVE);

ff.setVisible(true);
String dir=ff.getDirectory();
String name=ff.getFile();
if(dir==null||name==null){
System.out.println("no select");
return;
}

try{
System.out.println("dir="+dir+"\tname="+name);
ObjectOutputStream out=new ObjectOutputStream(new BufferedOutputStream(
new FileOutputStream(new File(dir,name))));

out.writeObject(toolList);
out.flush();
out.close();
}catch(IOException e3){e3.printStackTrace();}

}

if(e.getActionCommand().equals("打开(O)")) {
FileDialog ff=new FileDialog(MinidrawPad.this,"打开文件",
FileDialog.LOAD);

ff.setVisible(true);
String dir=ff.getDirectory();
String name=ff.getName();

if(dir==null||name==null){
return;
}
try{
ObjectInputStream in=new ObjectInputStream(new BufferedInputStream(
new FileInputStream(new File(dir,name))));
toolList=(ArrayList<ToolDraws>)in.readObject();
drawpanel.repaint();

}catch(Exception ee){ee.printStackTrace();}

}

}

}

class DrawPanel extends JPanel{

public void paint(Graphics g){

System.out.println("toolListSize:"+toolList.size());
super.paint(g);
if(currentSelect==10){
g.setColor(Color.black);
g.drawOval(x2, y2, 10, 10);}
g.setColor(Color.red);
for(int j=0;j<toolList.size();j++){
if(toolList.get(j)!=null){

toolList.get(j).draw(g);}
}
}

}

public static void main(String arg[]){
try{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}catch(Exception e){e.printStackTrace();}

new MinidrawPad();
}

}

class ToolDraws implements Serializable{
Color color;
Stroke stroke;
int x1=0,y1=0,x2=0,y2=0;
public void draw(Graphics g){}
}

class Will extends ToolDraws{
public void draw(Graphics g){
//
g.drawLine(x1, y1, x2, y2);
}
}

class Line extends ToolDraws{
public void draw(Graphics g){
g.drawLine(x1, y1, x2, y2);
}
}

class Rect extends ToolDraws{
public void draw(Graphics g){
g.drawRect(Math.min(x1,x2),Math.min(y1,y2),
Math.abs(x2-x1), Math.abs(y2-y1));
}
}

class Rect_f extends ToolDraws{
public void draw(Graphics g){
g.fillRect(Math.min(x1,x2),Math.min(y1, y2),
Math.abs(x2-x1),Math.abs(y2-y1));
}
}

class Oval extends ToolDraws{
public void draw(Graphics g){
g.drawOval(Math.min(x1,x2),Math.min(y1, y2),
Math.abs(x2-x1),Math.abs(y2-y1));
}
}

class Oval_f extends ToolDraws{
public void draw(Graphics g){
g.fillOval(Math.min(x1,x2), Math.min(y1, y2),
Math.abs(x1-x2), Math.abs(y1-y2));
}
}

class Circle extends ToolDraws{
public void draw(Graphics g){
g.drawOval(Math.min(x1,x2),Math.min(y1, y2),
Math.abs(x2-x1),Math.abs(y2-y1));
}
}

class Circle_f extends ToolDraws{
public void draw(Graphics g){
g.fillOval(Math.min(x1,x2),Math.min(y1, y2),
Math.abs(x2-x1),Math.abs(y2-y1));
}
}

class Roundrect extends ToolDraws{
public void draw(Graphics g){
/*drawRoundRect(int x, int y, int width, int height, int arcWidth, int arcHeight)
用此图形上下文的当前颜色绘制圆角矩形的边框。*/
g.drawRoundRect(Math.min(x1,x2), Math.min(y1, y2),
Math.abs(x1-x2), Math.abs(y1-y2),Math.abs(x1-x2)/5,
Math.abs(y1-y2)/5);
}
}

class Roundrect_f extends ToolDraws{
public void draw(Graphics g){
g.fillRoundRect(Math.min(x1,x2), Math.min(y1, y2),
Math.abs(x1-x2), Math.abs(y1-y2),Math.abs(x1-x2)/5,
Math.abs(y1-y2)/5);
}
}

class Rub extends ToolDraws{
public void draw(Graphics g){
g.setColor(Color.white);

g.fillOval(x1,y1,10,10);
}
}

//这个是我以前写的，有些功能未写完，但是你的要求还是实现了
//我还有个写的很完整的，搞得不知道那去了，所以，就发个不完整的拉
//

Answer 4

我以前写过一个 有现成的程序 你留邮箱我发给你

很简单的实现鼠标画线、方块、椭圆
还有是否填充和颜色选择
双缓冲区 保留之前图案 刷新不闪屏的