Java如何实现简单小画板

2023-07-02 08:07:37 876人浏览安东尼

摘要

今天小编给大家分享一下Java如何实现简单小画板的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。Java制作简单画板，包括两个

今天小编给大家分享一下Java如何实现简单小画板的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。

Java制作简单画板，包括两个类，一个主要画板类Drawpad，一个画板监听器DrawListener类。

Drawpad类，包括画板，画板功能设计，保存图片等

package Java课程设计;import java.awt.Graphics;import javax.imageio.ImageIO;import javax.print.DocFlavor.STRING;import javax.swing.ImageIcon;import javax.swing.JDialog;import javax.swing.JFileChooser;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JMenu;import javax.swing.JMenuBar;import javax.swing.JMenuItem;import javax.swing.JOptionPane;import javax.swing.JPanel;import javax.swing.JTextArea;import javax.swing.JTextField;import javax.swing.UIManager;import javax.swing.UnsupportedLookAndFeelException;import java.awt.AWTException;import java.awt.BasicStroke;import java.awt.BorderLayout;import java.awt.Color;import java.awt.Component;import java.awt.Container;import java.awt.Dimension;import java.awt.Font;import java.awt.Graphics2D;import java.awt.Rectangle;import java.awt.Robot;import java.awt.Shape;import java.awt.Window;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.image.BufferedImage;import java.awt.image.ColORModel;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.util.ArrayList;import javax.swing.JButton;import javax.swing.filechooser.FileNameExtensionFilter;public class Drawpad {     static Color color1;public static void main(String[] args) {    Drawpad dp = new Drawpad();    dp.initUI();     }     //创建一个JFrame图形窗口    public void initUI() {        JFrame jf = new JFrame();        jf.setTitle("创意画图板(勿拖动)");        jf.setSize(1500,1000);        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//关闭时退出        jf.setLocationRelativeTo(null);//居中，不用定位窗口大小        //创建字体，之后所有的字体为该字体        Font f=new Font("方正仿宋简体", Font.BOLD, 20);        //创建画笔监听器        DrawListener  dl = new DrawListener();        //创建读取图片BufferedImage(将图片加载到drawPanel面板中)和画笔g，画笔g为在保存图片上进行图画。                BufferedImage bi = new BufferedImage(1300,800, BufferedImage.TYPE_INT_ARGB);                Graphics2D g = bi.createGraphics();                //初始化时填充白色                g.setColor(Color.WHITE);                //先将图片填充为白色                g.fillRect(0, 0, 1300,800);                                        //设置增加菜单栏，包括保存和新建两个按钮        JMenuBar box=new JMenuBar();        //在窗体上加菜单条,做一个菜单条,是菜单条，不是工具栏        //创建menubtn1保存按钮，并加上监听器，以图片的形式保存绘画板上的内容        JButton menubtn1=new JButton("保存");        //为保存按钮注册监听器          menubtn1.addActionListener(new ActionListener(){                 @Override                 public void actionPerformed(ActionEvent arg0) {                     //创建文件保存窗口                     JFileChooser f=new JFileChooser("保存");                     int returnVal = f.showSaveDialog(null);                                         File    file1=null;                    if(returnVal == JFileChooser.APPROVE_OPTION) {                        file1 =f.getSelectedFile();                        String name = f.getName(file1);                        try {                                                        ImageIO.write(bi, "PNG", new File(f.getCurrentDirectory(),name+".png"));                        } catch (IOException e) {                            //需抛出异常                            // TODO Auto-generated catch block                            e.printStackTrace();                        }                    }                 }              });                           //创建menubtn3退出按钮，并加上监听器，退出程序          JButton menubtn3=new JButton("退出");          menubtn3.addActionListener(new ActionListener(){                   @Override                   //获取当前画笔粗细                   public void actionPerformed(ActionEvent arg0) {                       int ret=JOptionPane.showConfirmDialog(null, "你确定要退出吗", "确认退出", JOptionPane.YES_NO_OPTION);                       if(ret==JOptionPane.YES_OPTION){                           //“确认”退出程序                           System.exit(0);                       }                   }                });          box.add(menubtn1);         // box.add(menubtn2);          box.add(menubtn3);        //jf.setJMenuBar(box);                jf.setJMenuBar(box);                //jf用BorderLayout布局                //北边,画板模式功能栏        JPanel funcPanel=new JPanel();        jf.add(funcPanel,BorderLayout.NORTH);                //中间,画布        JPanel drawPanel=new JPanel();        jf.add(drawPanel,BorderLayout.CENTER);        drawPanel.setPreferredSize(new Dimension(1000,700));        drawPanel.setBackground(dl.background);        //一定要在画布上加上监听器!!1若画布没有加上监听器，无法显示        drawPanel.addMouseListener(dl);        drawPanel.addMouseMotionListener(dl);                //南边,为画笔颜色选择按钮        JPanel colorPanel=new JPanel();        jf.add(colorPanel,BorderLayout.SOUTH);                //右边,为选择背景颜色按钮、画笔粗细选择按钮        JPanel backgroundPanel=new JPanel();        jf.add(backgroundPanel,BorderLayout.EAST);        backgroundPanel.setPreferredSize(new Dimension(150,1000));                //左边,获取当前状态如:背景颜色、画笔颜色、画笔性质        JPanel nowPanel=new JPanel();        jf.add(nowPanel,BorderLayout.WEST);        nowPanel.setPreferredSize(new Dimension(180,1000));                //左边放入当前状态Panel        nowPanel.setBackground(Color.WHITE);         JLabel label2=new JLabel("当前背景颜色");          label2.setFont(f);           nowPanel.add(label2);           //放入当前背景颜色           JButton nowbackgroundColor=new JButton();           nowbackgroundColor.setPreferredSize(new Dimension(60,60));           nowbackgroundColor.setBackground(Color.WHITE);//背景初始化为灰色           nowPanel.add(nowbackgroundColor);           //放入当前画笔           JLabel label3=new JLabel("请选择画笔模式");              label3.setFont(f);               nowPanel.add(label3);           //放入当前画笔颜色           JButton nowColor=new JButton();           nowColor.setPreferredSize(new Dimension(60,60));           nowColor.setBackground(Color.BLACK);//画笔颜色初始化为黑色色           nowPanel.add(nowColor);                      //获取当前画笔模式            JLabel label4=new JLabel("当前画笔模式");              label4.setFont(f);               nowPanel.add(label4);               JTextField text=new JTextField(dl.btncontent); //获得选择画笔模式的按钮内容，得到当前画笔模式               text.setPreferredSize(new Dimension (160,60));               text.setFont(f);               text.setEditable(false);  //不可改            nowPanel.add(text);            //获取当前画笔粗细状态            JLabel label6=new JLabel("当前画笔粗细(中)");  //默认粗细为中              label6.setFont(f);               nowPanel.add(label6);               JTextField text1=new JTextField("请选择画笔粗细");               text1.setPreferredSize(new Dimension (160,60));               text1.setFont(f);               text1.setEditable(false); //不可编辑            nowPanel.add(text1);            //输入需要添加的文字            JLabel label7=new JLabel("请输入文字:");              label7.setFont(f);               nowPanel.add(label7);               JTextField text2=new JTextField();               text2.setPreferredSize(new Dimension (160,60));               text2.setFont(f);               nowPanel.add(text2);                JLabel label8=new JLabel("请输入文字样式:");                  label8.setFont(f);                   nowPanel.add(label8);                   JTextField text3=new JTextField("方正仿宋简体");                   text3.setPreferredSize(new Dimension (160,60));                   text3.setFont(f);                   nowPanel.add(text3);                   JLabel label9=new JLabel("请输入文字大小:");                      label9.setFont(f);                       nowPanel.add(label9);                       JTextField text4=new JTextField("20");                       text4.setPreferredSize(new Dimension (160,60));                       text4.setFont(f);                       nowPanel.add(text4);            //为获取文字内容加一个按钮并加上监听器               JButton getcontent=new JButton("获取文字");               getcontent .setFont(f);                getcontent.setBackground(Color.YELLOW);                getcontent.addActionListener(new ActionListener(){                    @Override                    public void actionPerformed(ActionEvent e) {                         String content=text2.getText();                        String mode=text3.getText();                        String size=text4.getText();                        dl.mode=mode; //获取文字样式                           dl.content=content; //获取文字内容                           dl.size=size; //获取文字大小                    }                 });                nowPanel.add(getcontent);                                //最后在当前状态画板中加一个清除画布内容的功能                JButton clear=new JButton("清除");                  clear.setFont(f);                    clear.setBackground(Color.RED);                    clear.addActionListener(dl);                    nowPanel.add(clear);                            //添加按钮到北边（每个按钮写两行代码太多，通过数组方式添加按钮）                //加入标签（选择画笔模式）                JLabel labelh =new JLabel("选择画笔模式");                labelh.setFont(f);                funcPanel.add(labelh);                //将按钮名字保存在数组中，后依次存储        String[] btnstr= {"画笔","直线","矩形","填充矩形","圆","填充圆","弧线","喷枪","波形","分形","长方体","九宫格递归","文字","橡皮"};        //将画笔状态按钮防置panel中        for( int i=0;i<btnstr.length;i++) {            JButton btn=new JButton(btnstr[i]);            funcPanel.add(btn);            btn .setFont(f);            btn.setBackground(Color.white);            //加上画笔监听器            btn.addActionListener(dl);            //加上监听器：获取当前 画笔模式            btn.addActionListener(new ActionListener(){                @Override                public void actionPerformed(ActionEvent e) {                    text.setText(btn.getText()); //在当前模式加入选取的画笔模式                }             });                    };                //在BrderLayout布局SOUTH添加选择颜色按钮        JLabel label =new JLabel("选择画笔(橡皮)颜色");        label.setFont(f);        colorPanel.add(label);                 //添加颜色按钮        Color[] colorArray = { Color.BLUE, Color.GREEN, Color.RED,                 Color.BLACK,Color.ORANGE,Color.PINK,Color.CYAN,                Color.MAGENTA,Color.DARK_GRAY,Color.GRAY,                Color.LIGHT_GRAY,Color.YELLOW,Color.WHITE};                //在布局管理器中添加颜色按钮        for( int i=0;i<colorArray.length;i++) {                        JButton button = new JButton();            button.setBackground(colorArray[i]);            button.setPreferredSize(new Dimension(50, 50));            button.addActionListener(dl);            colorPanel.add(button);            //获取当前状态的画笔颜色            button.addActionListener(new ActionListener(){                @Override                public void actionPerformed(ActionEvent e) {                    nowColor.setBackground(button.getBackground());  //在当前画笔颜色按钮加入选择的按钮颜色                }             });        };              funcPanel.setBackground(Color.gray);            //添加背景主板颜色按钮，并设置监听器（背景颜色为按钮颜色）      JLabel label1=new JLabel("选择背景颜色");      label1.setFont(f);       backgroundPanel.add(label1);      Color[] backgroundArray= { Color.GREEN, Color.RED,          Color.ORANGE,Color.PINK,Color.CYAN,              Color.MAGENTA,Color.DARK_GRAY,Color.GRAY,              Color.LIGHT_GRAY,Color.YELLOW,Color.WHITE,Color.BLACK};      //将按钮加入进去      for( int i=0;i<backgroundArray.length;i++) {                      JButton button = new JButton();          button.setBackground(backgroundArray[i]);          button.setPreferredSize(new Dimension(50, 50));          backgroundPanel.add(button);          //添加监听器，按下按钮改变背景颜色，同时体现当前状态        button.addActionListener(new ActionListener(){            @Override            public void actionPerformed(ActionEvent arg0) {                drawPanel.setBackground(button.getBackground()); //将背景颜色改为选取的背景颜色                color1=button.getBackground();                dl.background=color1;  //将背景颜色传给DrawListener中的变量                System.out.println(color1);                g.setColor(color1);                g.fillRect(0, 0, 1300,800);  //图片画笔填充背景颜色                nowbackgroundColor.setBackground(button.getBackground());            }         });        };                //添加选择画笔粗细的按钮,可选择画笔的粗细        JLabel label5=new JLabel("选择画笔粗细");          label5.setFont(f);           backgroundPanel.add(label5);           String[] Size={"细","中","粗"};           //选择画笔模式的按钮           for(int i=0;i<3;i++){               JButton graphsize=new JButton(Size[i]);               graphsize.setFont(new Font("宋体", Font.BOLD, 15));               graphsize.setBackground(Color.WHITE);               graphsize.setPreferredSize(new Dimension(50, 50));               backgroundPanel.add(graphsize);               graphsize.addActionListener(dl);               graphsize.addActionListener(new ActionListener(){                   @Override                   //获取当前画笔粗细                   public void actionPerformed(ActionEvent e) {                       text1.setText(graphsize.getText()); //获取当前画笔模式                   }                });           }        jf.setVisible(true);        // 获取这个界面的ｇｒａｐｈｉｃｓ属性, 画笔 g        //Graphics2D g = (Graphics2D) drawPanel.getGraphics();        //drawPanel.paintComponent(g);         Graphics2D g1= (Graphics2D) drawPanel.getGraphics();                //为画笔添加监听器        drawPanel.addMouseListener(dl);        dl.g =  g1;// 右传左         dl.g3 = g;// 右传左            }}

DrawListner类，画板功能监听器

package Java课程设计;import java.awt.BasicStroke;import java.awt.Color;import java.awt.Container;import java.awt.Dimension;import java.awt.Font;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.RenderingHints;import java.awt.Shape;import java.awt.event.MouseEvent;import java.awt.event.MouseListener;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.MouseMotionListener;import java.awt.geom.AffineTransform;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.JTextField;import java.awt.Color;import java.util.ArrayList;import java.util.Random;import Java课程设计.Drawpad;public class DrawListener implements MouseListener,ActionListener,MouseMotionListener {    //获取画笔    Graphics2D g;    //获取在保存图片上的画笔        Graphics2D g3;    //获取按钮内容    String btnstr;    Color background=Color.white; //背景颜色默认为白色    Color graphcolor=Color.BLACK; //画笔颜色默认为黑色    JButton btn;    int x1, y1, x2, y2;// 声明坐标变量     int x3=400;    int y3=0;    int graphsize=3;//默认为中等画笔    String btncontent="画笔"; //默认画笔模式为画笔    String content;  //获取文字中的文字内容    String mode="方正仿宋简体";  //文字样式默认为“方正仿宋简体”    String size="20";        //九宫格递归方法,画出九宫格    public void dg(int x,int y,int width,int height) {        //九宫格函数，九宫格的实现         if(width<3) {                return;                }        if(width>90) {        g.fillRect(x+width/3, y+height/3, width/3, height/3);        g3.fillRect(x+width/3, y+height/3, width/3, height/3);        dg(x, y, width/3, height/3);        dg(x+width/3, y, width/3, height/3);        dg(x+(width/3)*2, y, width/3, height/3);        dg(x, y+height/3, width/3, height/3);        dg(x, y+(height/3)*2, width/3, height/3);                dg(x+width/3, y+height/3, width/3, height/3);        dg(x+width/3, y+(height/3)*2, width/3, height/3);                dg(x+(width/3)*2, y+height/3, width/3, height/3);        dg(x+(width/3)*2, y+(height/3)*2, width/3, height/3);                }      //九宫格的实现       else {           g.drawOval(x+width/3, y+height/3, width/3, height/3);           g3.drawOval(x+width/3, y+height/3, width/3, height/3);           dg(x, y, width/3, height/3);           dg(x+width/3, y, width/3, height/3);            dg(x+(width/3)*2, y, width/3, height/3);            dg(x, y+height/3, width/3, height/3);            dg(x, y+(height/3)*2, width/3, height/3);                        dg(x+width/3, y+height/3, width/3, height/3);            dg(x+width/3, y+(height/3)*2, width/3, height/3);                        dg(x+(width/3)*2, y+height/3, width/3, height/3);            dg(x+(width/3)*2, y+(height/3)*2, width/3, height/3);       }            }    //判断是颜色按钮还是画笔按钮,改变的全部是画笔按钮    public void actionPerformed(ActionEvent e) {        btnstr=e.getActionCommand();  //获取按钮的文字内容        //g.setColor(Color.black);        //如果为颜色按钮，将画笔改颜色        if(btnstr.equals("清除")){            //重新填充背景，同时将画笔置为背景颜色             System.out.println(background);            g.setColor(background);//保存图片画笔填充背景颜色            g.fillRect(0, 0, 1300, 800);            g3.setColor(background);//画笔重新填充背景            g3.fillRect(0, 0, 1300, 800);            g.setColor(graphcolor);            g3.setColor(graphcolor);        }        else{        if(btnstr.equals("")) {            //获取点击内容,将其内容强制转换成JButton           btn=(JButton) e.getSource();            //获取颜色按钮颜色           graphcolor=btn.getBackground();                    }        //若为画笔粗细，获取粗细大小        else if(btnstr.equals("细")){            graphsize=1;  //画笔大小为细，大小size为1        }        else if(btnstr.equals("中")){            graphsize=3;        }        else if(btnstr.equals("粗")){            graphsize=5;        }        else{            btncontent=btnstr; //获取画笔模式按钮的内容        }        }    }    //鼠标点击方法    @Override    public void mouseClicked(MouseEvent e) {        System.out.println("点击");    }   //鼠标按下方法    @Override    public void mousePressed(MouseEvent e) {        System.out.println("按下");        x1=e.getX();        y1 =e.getY();    }    //重写鼠标释放时的方法    @Override    public void mouseReleased(MouseEvent e) {        g.setColor(graphcolor);//获取保存画笔的颜色        g3.setColor(graphcolor); //获取画板画笔的颜色                x2=e.getX();        y2 =e.getY();        //选取画笔模式为直线时        if(btncontent.equals("直线")) {            g.setStroke(new BasicStroke(graphsize)); //保存画笔进行画图        g.drawLine(x1, y1, x2, y2);//画笔画直线        g3.setStroke(new BasicStroke(graphsize));//置画笔大小        g3.drawLine(x1, y1, x2, y2);        }        //选取画笔模式为波形时        else if(btncontent.equals("波形")) {            //波形函数            g.setStroke(new BasicStroke(graphsize)); //置画笔大小            g3.setStroke(new BasicStroke(graphsize));            double x4 = 0,y4 = 0;            double a2=1.40,b2=1.56,c2=1.40,d2=-6.56;            //波形函数            for(int i=0;i<5000;i++) {                double x5=Math.sin(a2*x4)-Math.cos(b2*y4);                double y5=Math.sin(c2*x4)-Math.cos(d2*y4);                x4=x5;                y4=y5;                int px=(int)(x5*100+x1);                int py=(int)(y5*100+y1);                //画波形                g.drawLine(px, py, px, py);                g3.drawLine(px, py, px, py);                }        }        //选取画笔模式为矩形时        else if(btncontent.equals("矩形")) {            g.setStroke(new BasicStroke(graphsize)); //获取矩形画笔的大小            g.drawRect(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2-x1), Math.abs(y2-y1));//画矩形            g3.setStroke(new BasicStroke(graphsize));             g3.drawRect(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2-x1), Math.abs(y2-y1));        }        //选取的画笔模式为填充矩形        else if(btncontent.equals("填充矩形")){            //画填充矩形            g.fillRect(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2-x1), Math.abs(y2-y1));            g3.fillRect(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2-x1), Math.abs(y2-y1));        }        //长方体函数        else if(btncontent.equals("长方体")){            g.setStroke(new BasicStroke(graphsize));//获取长方体画笔大小             g.setColor(btn.getBackground());//将画笔颜色置选择画笔颜色按钮颜色             //长方体函数                g.fillRect(Math.min(x1,x2),Math.min(y1,y2),Math.abs(x1-x2),Math.abs(y1-y2));                g3.setStroke(new BasicStroke(graphsize));                 g3.setColor(btn.getBackground());                    g3.fillRect(Math.min(x1,x2),Math.min(y1,y2),Math.abs(x1-x2),Math.abs(y1-y2));                int a,b,c,d;                a=Math.min(x1, x2);                b=Math.max(x1, x2);                c=Math.min(y1, y2);                d=Math.max(y1, y2);                int m=(int)((b-a)*Math.cos(Math.PI/4)*Math.sin(Math.PI/4));                int n=(int)((b-a)*Math.cos(Math.PI/4)*Math.sin(Math.PI/4));                //顶面                g.setColor(btn.getBackground());                g.fillPolyGon(new int[] {a, a+m, b+m,b},new int[] {c,c-n,c-n,c},4);                //右侧面                g.setColor(btn.getBackground());                g.fillPolygon(new int[] {b, b, b+m,b+m},new int[] {c,d,d-n,c-n},4);                g3.setColor(btn.getBackground());                g3.fillPolygon(new int[] {a, a+m, b+m,b},new int[] {c,c-n,c-n,c},4);                //右侧面                g3.setColor(btn.getBackground());                g3.fillPolygon(new int[] {b, b, b+m,b+m},new int[] {c,d,d-n,c-n},4);        }        //分形函数        else if(btncontent.equals("分形")){            g.setStroke(new BasicStroke(graphsize));  //获取画笔大小            g3.setStroke(new BasicStroke(graphsize));            double x = 0,y = 0;            //分形函数实现            double a1=-1.8,b=-2.0,c=-0.5,d=-0.9;            for(int i=0;i<5000;i++) {            double x3=Math.sin(a1*y)-c*Math.cos(a1*x);            double y3=Math.sin(b*x)-d*Math.cos(b*y);            x=x3;            y=y3;            int px=(int)(x3*100+x1);            int py=(int)(y3*100+y1);            g.drawLine(px, py, px, py);            g3.drawLine(px, py, px, py);        }        }        //画圆        else if(btncontent.equals("圆")) {            g.setStroke(new BasicStroke(graphsize));//获取画笔大小            g.drawOval(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2-x1), Math.abs(y2-y1));//画圆            g3.setStroke(new BasicStroke(graphsize));            g3.drawOval(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2-x1), Math.abs(y2-y1));        }        //画填充圆        else if(btncontent.equals("填充圆")){            g.fillOval(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2-x1), Math.abs(y2-y1));//画填充圆            g3.fillOval(Math.min(x1, x2), Math.min(y1, y2), Math.abs(x2-x1), Math.abs(y2-y1));        }        //当选取模式为文字        else if(btncontent.equals("文字")){            //获取画笔大小            g.setStroke(new BasicStroke(15));        Font font = new Font(mode, Font.BOLD, Integer.parseInt(size)); //获得文字内容，文字大小，文字样式             g.setFont(font); //在画笔中置文字样式和大小            g.drawString(content, x1, y1); //写上文字内容            g3.setStroke(new BasicStroke(15));             g3.setFont(font);//放入文字样式和大小            g3.drawString(content, x1, y1);        }        //当画笔模式为弧线时        else if(btncontent.equals("弧线")){            g.setStroke(new BasicStroke(graphsize));//获取画笔大小            //弧线函数             g.drawArc(x1, y1, 100, 60, 0, 180);             g3.setStroke(new BasicStroke(graphsize));             g3.drawArc(x1, y1, 100, 60, 0, 180);        }        //九宫格递归，调用九宫格函数        else if(btncontent.equals("九宫格递归")) {            //九宫格递归实现              dg(0,50,600,600);          }        System.out.println("释放");            }    @Override    //鼠标进入方法    public void mouseEntered(MouseEvent e) {        System.out.println("进入");    }    @Override    //鼠标离开界面方法    public void mouseExited(MouseEvent e) {        System.out.println("离开");    }    @Override    public void mouseMoved(MouseEvent e) {            }    //重写鼠标移动函数    @Override    public void mouseDragged(MouseEvent e) {        g.setColor(graphcolor); //获取画笔颜色        g3.setColor(graphcolor);        // TODO Auto-generated method stub        x2=e.getX();        y2 =e.getY();        //当为画笔时        if(btncontent.equals("画笔")){                    g.setStroke(new BasicStroke(graphsize));    //获取当前画笔大小                //画笔实现                g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);                g.drawLine(x1, y1, x2, y2);                g3.setStroke(new BasicStroke(graphsize));                            g3.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);                g3.drawLine(x1, y1, x2, y2);                x1 = x2;                y1 = y2;                }        //橡皮擦         if(btncontent.equals("橡皮")){             //将画笔颜色置为背景颜色             g.setColor(background);             g3.setColor(background);            g.setStroke(new BasicStroke(30));    //将橡皮擦的大小置大小为30                                    g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);            g.drawLine(x1, y1, x2, y2);                        g3.setStroke(new BasicStroke(30));                                        g3.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);            g3.drawLine(x1, y1, x2, y2);            x1 = x2;            y1 = y2;               //使用过后，将画笔颜色重新置为原来颜色            g.setColor(graphcolor);            g3.setColor(graphcolor);        }         //喷枪函数                 else if(btncontent.equals("喷枪")){                g.setStroke(new BasicStroke(graphsize));      //不用加粗，获取画笔大小                                        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);                g3.setStroke(new BasicStroke(graphsize));      //不用加粗                                        g3.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);                //喷枪实现函数                for(int k=0;k<20;k++){                    Random i=new Random();                           int a=i.nextInt(10);                    int b=i.nextInt(20);                    g.drawLine(x2+a, y2+b, x2+a, y2+b);                    g3.drawLine(x2+a, y2+b, x2+a, y2+b);        }        }            }}

画板演示:

Java如何实现简单小画板