Java如何实现简单小画板

发布时间:2022-06-13 14:01:41 作者:iii
来源:亿速云 阅读:163

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。

1、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();
                        }

                    }
                 }
              });
         /*JButton menubtn2=new JButton("打开");
          //为打开按钮注册监听器
          menubtn1.addActionListener(new ActionListener(){
               @Override
               //获取当前画笔粗细
               public void actionPerformed(ActionEvent arg0) {
                   BufferedImage bimg = null;
                   JFileChooser f=new JFileChooser("打开");
                 int returnVal = f.showOpenDialog(null);
                 
                File    file1=null;
                if(returnVal == JFileChooser.APPROVE_OPTION) {
                    file1 =f.getSelectedFile();
                    String name = f.getName(file1);
                    try {
                      
                    } catch (IOException e) {
                        // 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
        
    }
}

2、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

保存图片:

Java如何实现简单小画板

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