一起来画画

知识点：

1. JFrame窗体类关键属性、方法和事件的应用
2. Canvas画板类的关键方法和事件的应用
3. 窗体菜单栏的创建和层级关系
4. 工具栏、按钮的配合使用
5. 鼠标点击、移动事件的使用
6. AWT绘图方法的使用

Swing组件：

• JFrame窗体类
• JWindow无边框窗体类
• JButton窗体类
• JToggleButton按钮类
• JMenuBar菜单栏类
• JMenu菜单类
• JMenuItem菜单项类

Swing事件监听：

• 鼠标点击
• 鼠标拖曳

Java技术：

• Graphics2D绘图类
• Java继承
• 主类、主方法概念
• File文件类
• Image图片类
• Ellipse2D圆形图形类
• Rectangle2D方形图形类

 1.创建项目和导入资源

在Package Explorer的Other Projects，右键-New-Other-Java Project-next-(输入项目名:一起来画画)Finish;

在项目名上，右键-New-Folder-(选择文件夹：一起来画画,在Folder name输入:lib)Finish;

将外部包DrawUtil.mr.jar复制到lib里，然后在项目名上，右键-Build Path-Configure Build Path-Libraries-Add JARs...-选中"一起来画画/lib/DrawUtil.mr.jar"-OK;

2.编码

package com.mr.draw;

import javax.swing.JFrame;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;

import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;

import java.awt.BorderLayout;
import javax.swing.ButtonGroup;
import javax.swing.JButton;//按钮类
import javax.swing.JToggleButton;///画线类
import javax.swing.JToolBar;//工具栏类

import java.awt.BasicStroke;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;//调整画笔粗细

import javax.swing.JColorChooser;//实现添加颜色功能

import java.awt.geom.Ellipse2D;
import java.awt.geom.Rectangle2D;
import com.mr.util.FrameGetShape;
import com.mr.util.ShapeWindow;
import com.mr.util.Shapes; ///实现绘制图形功能

import com.mr.util.DrawImageUtil;//实现图片保存功能

import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;//实现 添加菜单栏

import java.awt.AlphaComposite;
import java.awt.Font;
import javax.swing.JOptionPane;//实现添加水印，为自己作品署名

import java.awt.Image;
import java.awt.Point;
import java.awt.Toolkit;//工具箱
import java.awt.Cursor;//光标，实现更改鼠标图标功能
import javax.swing.ImageIcon;  

//画图主窗体
public class DrawPictureFrame extends JFrame implements FrameGetShape{//继承窗体类,实现绘制图形的接口
    //创建一个8位BGR颜色分量的图像
    BufferedImage image = new BufferedImage(570,390,BufferedImage.TYPE_3BYTE_BGR);
    Graphics gs = image.getGraphics();
    Graphics2D g = (Graphics2D)gs;
    DrawPictureCanvas canvas = new DrawPictureCanvas();        //创建画布对象
    Color foreColor = Color.red;                            //前景色
    Color backgroundColor = Color.green;                    //背景色
    
    int x=-1;
    int y=-1;//上一次鼠标绘制点的横纵坐标
    boolean rubber=false;//橡皮识别变量
    
    private JToolBar toolBar;//工具栏目
    private JButton eraserButton;
    private JToggleButton strokeButton1;
    private JToggleButton strokeButton2;
    private JToggleButton strokeButton3;//细中粗按钮
    private JButton backgroundButton;
    private JButton foregroundButton;
    private JButton clearButton;
    private JButton saveButton;
    private JButton shapeButton;//图形按钮
    boolean drawShape = false;
    Shapes shape;
    private JMenuItem strokeMenuItem1;
    private JMenuItem strokeMenuItem2;
    private JMenuItem strokeMenuItem3;
    private JMenuItem clearMenuItem;
    private JMenuItem foregroundMenuItem;
    private JMenuItem backgroundMenuItem;
    private JMenuItem eraserMenuItem;
    private JMenuItem exitMenuItem;//退出菜单
    private JMenuItem saveMenuItem;
    private JMenuItem shuiyinMenuItem;//水印菜单
    private String shuiyin = "";//水印字符内容
    private PictureWindow picWindow;//简笔画展示窗体
    private JButton showPicButton;//展开简笔画按钮
    
    
    public DrawPictureFrame() 
    {
        setResizable(false);                                 // 窗体大小不能改变
        //setTitle("画图程序");
        setTitle("画图程序(水印内容:[" + shuiyin + "] )" );
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     // 窗体关闭则立即停止程序
        setBounds(500, 100, 574, 460);                         // 设置窗口的位置和宽高
        
        init();//组件初始化
        addListener();//添加组件监听
    }
    
    private void init()
    {
        g.setColor(backgroundColor);//用前景色设置绘图对象的颜色
        g.fillRect(0, 0, 570, 390);//用背景色填充整个画布,第一个0和570表示位置从0开始到57
        g.setColor(foreColor);//用前景色设置绘图对象的颜色
        canvas.setImage(image);//设置画布的图像
        getContentPane().add(canvas);//将画布添加到窗体容器默认布局中的中部位置
        
        toolBar = new JToolBar();//初始化工具栏
        toolBar.setFloatable(false);//工具栏固定
        getContentPane().add(toolBar,BorderLayout.NORTH);//将工具栏添加到窗体最北位置
        
        //showPicButton = new JButton("展开简笔画");
        showPicButton = new JButton();
        showPicButton.setToolTipText("展开简笔画");
        showPicButton.setIcon( new ImageIcon("src/img/icon/展开.png") );//需要导入ImageIcon
        toolBar.add(showPicButton);
        
        saveButton = new JButton("保存");
        toolBar.add(saveButton);
        toolBar.addSeparator();//添加工具栏
        strokeButton1 = new JToggleButton("细线");
        strokeButton1.setSelected(true);//细线按钮处于被选中状态
        toolBar.add(strokeButton1);
        
        strokeButton2 = new JToggleButton("粗线");
        toolBar.add(strokeButton2);
        
        strokeButton3 = new JToggleButton("较粗");
        toolBar.add(strokeButton3);
        toolBar.addSeparator();
        ButtonGroup strokeGroup = new ButtonGroup();//画笔粗细按钮组，保证同时只有一个被选中
        strokeGroup.add(strokeButton1);
        strokeGroup.add(strokeButton2);
        strokeGroup.add(strokeButton3);
        
        backgroundButton = new JButton("背景颜色");
        toolBar.add(backgroundButton);
        foregroundButton = new JButton("前景颜色");
        toolBar.add(foregroundButton);
        toolBar.addSeparator();
        
        shapeButton = new JButton("图形");
        toolBar.add(shapeButton);
        clearButton = new JButton("清除");
        toolBar.add(clearButton);
        eraserButton = new JButton("橡皮");
        toolBar.add(eraserButton);
        toolBar.addSeparator();
        
        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);
        
        JMenu systemMenu = new JMenu("系统");
        menuBar.add(systemMenu);
        shuiyinMenuItem = new JMenuItem("设置水印");
        systemMenu.add(shuiyinMenuItem);
        saveMenuItem = new JMenuItem("保存");
        systemMenu.add(saveMenuItem);
        systemMenu.addSeparator();
        exitMenuItem = new JMenuItem("退出");
        systemMenu.add(exitMenuItem);
        JMenu strokeMenu = new JMenu("线型");
        menuBar.add(strokeMenu);
        strokeMenuItem1 = new JMenuItem("细线");
        strokeMenu.add(strokeMenuItem1);
        strokeMenuItem2 = new JMenuItem("粗线");
        strokeMenu.add(strokeMenuItem2);
        strokeMenuItem3 = new JMenuItem("较线");
        strokeMenu.add(strokeMenuItem3);
        
        JMenu colorMenu = new JMenu("颜色");
        menuBar.add(colorMenu);
        foregroundMenuItem = new JMenuItem("前景颜色");
        colorMenu.add(foregroundMenuItem);
        backgroundMenuItem = new JMenuItem("背景颜色");
        colorMenu.add(backgroundMenuItem);
        
        JMenu editMenu = new JMenu("编辑");
        menuBar.add(editMenu);
        clearMenuItem = new JMenuItem("清除");
        editMenu.add(clearMenuItem);
        eraserMenuItem = new JMenuItem("橡皮");
        editMenu.add(eraserMenuItem);
        
        picWindow = new PictureWindow(DrawPictureFrame.this);
    }
    
    //动作监听
    private void addListener()
    {
        canvas.addMouseMotionListener(new MouseMotionAdapter(){
        
            public void mouseDragged( final MouseEvent e )//鼠标拖曳监听
            {
                if(x>0 && y>0)//如果x和y存在鼠标记录
                {
                    if(rubber)//如果是橡皮则画出背景色，相当于擦掉前景色
                    {
                        g.setColor(backgroundColor);
                        g.fillRect(x, y, 10, 10);
                    }
                    else //否则画出
                        g.drawLine(x,y,e.getX(),e.getY());
                }
                x=e.getX();
                y=e.getY();//上一次鼠标绘制点的横纵坐标
                canvas.repaint();//更新画布
            }
            public void mouseMoved(final MouseEvent arg0) {
                if(rubber)//如果使用橡皮
                {
                    Toolkit kit = Toolkit.getDefaultToolkit();//获得系统默认的组件工具包
                    Image img = kit.createImage("src/img/icon/鼠标橡皮.png");//利用工具包获取图片
                    Cursor c = kit.createCustomCursor(img,new Point(0,0),"clear");//参数为图片，光标热点和光标描述的字符串
                    setCursor(c);//使用自定义光标
                }
                else 
                    setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));//不是橡皮则是画笔，则设置光标为十字形
            }
        });
        canvas.addMouseListener(new MouseAdapter() {//鼠标点击监听
            public void mouseReleased( final MouseEvent arg0 )//按键抬起时
            {
                x=-1;
                y=-1;//将上一次鼠标绘制点的横纵坐标恢复成-1
                //改成x=11,y=11？？？
            }
            
            public void mousePressed(MouseEvent e)//当按键按下时
            {
                if( drawShape )//如果此时鼠标画的是
                {
                    switch( shape.getType() )//判断图形种类
                    {
                        case Shapes.YUAN:
                            int yuanX = e.getX()-shape.getWidth()/2;
                            int yuanY = e.getY()-shape.getHeigth()/2;
                            /*
                            System.out.println(e.getX()+"  "+e.getY());
                            System.out.println(shape.getWidth()/2+"  "+shape.getHeigth()/2);
                            System.out.println(yuanX+"  "+yuanY);*/
                            //创建圆形图形，根据长宽可能是椭圆，指定坐标和宽高
                            Ellipse2D yuan = new Ellipse2D.Double(yuanX,yuanY,shape.getWidth(),shape.getHeigth());
                            g.draw(yuan);
                            break;
                        case Shapes.FANG:
                            int fangX=e.getX()-shape.getWidth()/2;
                            int fangY=e.getY()-shape.getHeigth()/2;
                            Rectangle2D fang = new Rectangle2D.Double(fangX,fangY,shape.getWidth(),shape.getHeigth());
                            g.draw(fang);
                            break;
                    }
                    canvas.repaint();
                    drawShape = false;//画一个就不能画了
                }
            }
        });
        
        toolBar.addMouseMotionListener(new MouseMotionAdapter() {//工具栏添加鼠标移动监听
            public void mouseMoved(final MouseEvent arg0) {//鼠标移动时，设置鼠标指针的形状为默认光标
                setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
            }
        });
        
        //调整画笔粗细
        strokeButton1.addActionListener(new ActionListener() {//细线按钮添加监听
            public void actionPerformed(final ActionEvent arg0)//单击时
            {    //声明画笔的属性，粗细为1像素，线条末端无修饰，折线处呈尖角
                BasicStroke bs = new BasicStroke(1, BasicStroke.CAP_BUTT,BasicStroke.JOIN_MITER);
                g.setStroke(bs);//画图工具使用此笔
            }
        });
        strokeButton2.addActionListener(new ActionListener() {//中线按钮添加监听
            public void actionPerformed(final ActionEvent arg0)//单击时
            {    //声明画笔的属性，中线为2像素，线条末端无修饰，折线处呈尖角
                BasicStroke bs = new BasicStroke(2,BasicStroke.CAP_BUTT,BasicStroke.JOIN_MITER);
                g.setStroke(bs);//画图工具使用此笔
            }
            
        });
        strokeButton3.addActionListener(new ActionListener() {//粗线按钮添加监听
            public void actionPerformed(final ActionEvent arg0)//单击时
            {    //声明画笔的属性，粗线为4像素，线条末端无修饰，折线处呈尖角
                BasicStroke bs = new BasicStroke(4,BasicStroke.CAP_BUTT,BasicStroke.JOIN_MITER);
                g.setStroke(bs);//画图工具使用此笔
            }
        });
        
        //实现颜色添加功能
        backgroundButton.addActionListener( new ActionListener() {
            public void actionPerformed( final ActionEvent arg0 )
            {    //打开选择颜色对话框，参数依次是：符窗体、标题、默认选中的颜色（青色）
                Color bgColor = JColorChooser.showDialog(DrawPictureFrame.this, "选择颜色对话框", Color.CYAN);
                if ( bgColor !=null )///选中的颜色不是空的
                    backgroundColor = bgColor;//则将选中的颜色赋给背景色
                backgroundButton.setBackground(backgroundColor);
                g.setColor(backgroundColor);
                g.fillRect(0, 0, 570, 390);//画一个背景颜色的方形填满整个画布
                g.setColor(foreColor);
                canvas.repaint();//更新画布
            }
        });
        foregroundButton.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent arg0)
            {
                Color fColor = JColorChooser.showDialog(DrawPictureFrame.this, "选择颜色对话框", Color.CYAN);
                if(fColor != null)
                    foreColor = fColor;
                foregroundButton.setForeground(foreColor);
                g.setColor(foreColor);
            }
            
        });
        
        //清除按钮和橡皮按钮
        clearButton.addActionListener(new ActionListener() {
            public void actionPerformed( final ActionEvent arg0 ) {
                g.setColor(backgroundColor);
                g.fillRect(0, 0, 570, 390);//用背景色填充以达到清除效果，然后画笔换成前景色，继续作画
                g.setColor(foreColor);
                canvas.repaint();//更新画布
            }
        });    
        eraserButton.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent arg0)
            {
                if( eraserButton.getText().equals("橡皮") )
                {
                    rubber = true;
                    eraserButton.setText("画图");
                }
                else
                {
                    rubber = false;
                    eraserButton.setText("橡皮");
                    g.setColor(foreColor);
                    
                }
            }
        });
        
        
        //图形绘制按钮
        shapeButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e)//单击时
            {
                //创建图形选择组件
                ShapeWindow shapeWindow = new ShapeWindow(DrawPictureFrame.this);
                int shapeButtonWidth = shapeButton.getWidth();
                int shapeWindowWidth = shapeWindow.getWidth();
                int shapeButtonX = shapeButton.getX();
                int shapeButtonY = shapeButton.getY();
                int shapeWindowX = getX() - shapeButtonX - ( shapeWindowWidth-shapeButtonWidth )/2;
                int shapeWindowY = getY() - shapeButtonY + 80;
                shapeWindow.setLocation(shapeWindowX,shapeWindowY);
                shapeWindow.setVisible(true);//图形组件可见，如果是false点击图形啥都没有
            }
            
        });
        
        //保存按钮实现保存功能
        saveButton.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent arg0) {//单击时
                addWatermark();//添加水印
                DrawImageUtil.saveImage(DrawPictureFrame.this,image );//打印图片
            }
            
        });
        
        exitMenuItem.addActionListener(new ActionListener() {///退出菜单动作监听
            public void actionPerformed(final ActionEvent e)///单击时程序退出
            {
                System.exit(0);
            }
        });
        
        eraserMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent e) {
                if( eraserMenuItem.getText().contentEquals("橡皮") ) {
                    rubber = true;
                    eraserMenuItem.setText("画图");
                    eraserButton.setText("画图");
                }
                else
                {
                    rubber = false;
                    eraserMenuItem.setText("橡皮");
                    eraserButton.setText("橡皮");
                    g.setColor(foreColor);
                }
            }
        });
        
        clearMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent e) {
                g.setColor(backgroundColor);
                g.fillRect(0, 0, 570, 390);
                g.setColor(foreColor);
                canvas.repaint();
                
            }
        });
        
        strokeMenuItem1.addActionListener(new ActionListener() {//细线菜单添加动作监听
            public void actionPerformed(final ActionEvent e) {
                //像素为1，线条末端无修饰，折线处呈尖角
                BasicStroke bs = new BasicStroke(1,BasicStroke.CAP_BUTT,BasicStroke.JOIN_MITER);
                g.setStroke(bs);//画图工具使用此笔
                strokeButton1.setSelected(true);//细线按钮设为选中状态
            }
        });
        
        strokeMenuItem2.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent e) {
                BasicStroke bs = new BasicStroke(2,BasicStroke.CAP_BUTT,BasicStroke.JOIN_MITER);
                g.setStroke(bs);
                strokeButton2.setSelected(true);
            }
        });
        
        strokeMenuItem3.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent e) {
                BasicStroke bs = new BasicStroke(4,BasicStroke.CAP_BUTT,BasicStroke.JOIN_MITER);
                g.setStroke(bs);
                strokeButton3.setSelected(true);
            }
        });
        
        foregroundMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent e) {
                Color fColor = JColorChooser.showDialog(DrawPictureFrame.this, "选择颜色对话框", Color.CYAN);
                if( fColor != null )
                    foreColor = fColor;
                foregroundButton.setForeground(foreColor);
                g.setColor(foreColor);
            }
        });
        
        backgroundMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(final ActionEvent e) {
                Color bgColor = JColorChooser.showDialog(DrawPictureFrame.this, "选择颜色对话框", Color.CYAN);
                if( bgColor != null )
                    backgroundColor = bgColor;
                backgroundButton.setBackground(backgroundColor);
                g.setColor(backgroundColor);
                g.fillRect(0, 0, 570, 390);
                g.setColor(foreColor);
                canvas.repaint();
            }
        });
        
        saveMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                addWatermark();//添加水印
                DrawImageUtil.saveImage(DrawPictureFrame.this,image);//打印图片
            }
        });
        
        shuiyinMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                //输入对话框
                System.out.println("facai1");
                shuiyin = JOptionPane.showInputDialog(DrawPictureFrame.this,"你想添加什么水印？");
                System.out.println("facai2");
                if ( null == shuiyin)
                    shuiyin="";
                else 
                    setTitle("画图程序(水印内容：[ " + shuiyin + " ])");//修改窗体标题
                System.out.println("facai3");
            }
        });
        
        showPicButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                boolean isVisible = picWindow.isVisible();
                if(isVisible) {
                    showPicButton.setText("展开简笔画");
                    picWindow.setVisible(false);
                }
                else 
                {
                    showPicButton.setText("隐藏简笔画");
                    //重新指定简笔画展示窗体的显示位置
                    //横坐标 = 主窗体横坐标 - 简笔画窗体宽度 - 5； 纵坐标 = 主窗体纵坐标
                    picWindow.setLocation(getX()-picWindow.getWidth()-5,getY());
                    picWindow.setVisible(true);
                }
            }
        });
        
        
    
    }
    
    //添加水印
    private void addWatermark() {
        if( !"".equals(shuiyin.trim()) )///shuiyin变量删除头尾空白字符后 不等于空 
        {
            g.rotate(Math.toRadians(-30));//将图片旋转-30弧度
            Font font = new Font("楷体",Font.BOLD,72);//设置字体
            g.setFont(font);
            g.setColor(Color.GRAY);
            AlphaComposite alpha = AlphaComposite.SrcOver.derive(0.4f);//设置透明效果
            g.setComposite(alpha);
            g.drawString(shuiyin, 75, 400);//绘制文字
            canvas.repaint();
            g.rotate(Math.toRadians(30));//将旋转的图片再旋转回来
            alpha = AlphaComposite.SrcOver.derive(1f);//不透明效果
            g.setComposite(alpha);//使用不透明效果
            g.setColor(foreColor);//画笔恢复之前颜色
        }
    }
    
    //恢复展开简笔画按钮的文本内容，此方法供简笔画面板的"隐藏"按钮调用
    public void initShowPicButton() {
        showPicButton.setText("展开简笔画");
    }
    
    
    //FrameGetShape接口实现类，用于获得图形空间返回的被选中的图形
    public void getShape(Shapes shape)
    {
        this.shape=shape;//将返回的图形对象赋给类的全局变量
        drawShape = true;//画图形标识变量为true，说明现在鼠标画的是图形，而不是线条
    }
    
    
    
    

    public static void main(String[] args) 
    {
        DrawPictureFrame frame = new DrawPictureFrame();//创建窗体对象
        frame.setVisible(true);//让窗体可见
    }

}

package com.mr.draw;

import java.awt.Canvas;
import java.awt.Graphics;
import java.awt.Image;


public class DrawPictureCanvas extends Canvas{
    private Image image = null;//创建画板中展示的图片对象
    //设置画板中的图片
    public void setImage( Image image)
    {
        this.image = image;
    }
    //重写，在画布上绘制图像
    public void paint( Graphics g )
    {
        g.drawImage( image,0,0,null );
    }
    
    //重写，解决屏幕闪烁问题
    public void update( Graphics g )
    {
        paint(g);
    }
}

package com.mr.draw;

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JPanel;//面板
import javax.swing.JWindow;
import com.mr.util.BackgroundPanel;



public class PictureWindow extends JWindow {
    private JButton changeButton;
    private JButton hiddenButton;
    private BackgroundPanel centerPanel;
    File list[];
    int index;
    DrawPictureFrame frame;
    
    //构造方法
    public PictureWindow(DrawPictureFrame frame) {
        this.frame = frame;//构造参数的值赋给父窗体
        setSize(400,460);
        init();
        addListener();
    }
    
    private void init() {
        Container c = getContentPane();
        File dir = new File("src/img/picture");
        list = dir.listFiles();
        centerPanel = new BackgroundPanel(getListImage());
        c.add(centerPanel,BorderLayout.CENTER);//背景面板放到主容器的中部
        FlowLayout flow = new FlowLayout(FlowLayout.RIGHT);//右对齐流布局
        flow.setHgap(20);//水平间隔20像素
        JPanel southPanel = new JPanel();//创建南部面板
        southPanel.setLayout(flow);//使用刚才建好的流布局
        changeButton = new JButton("更换图片");
        southPanel.add(changeButton);
        hiddenButton = new JButton("隐藏");
        southPanel.add(hiddenButton);
        c.add(southPanel,BorderLayout.SOUTH);//南部面板放在主容器的南部
    }
    
    //添加监听
    private void addListener() {
        hiddenButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                setVisible(false);//隐藏按钮点击时窗体不可见
                frame.initShowPicButton();
            }
        });
        changeButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                centerPanel.setImage(getListImage());//更换图片按钮点击时背景面板重新载入图片
            }
        });
    }
    
    private Image getListImage() {
        String imgPath = list[index].getAbsolutePath();
        ImageIcon image = new ImageIcon(imgPath);
        index++;
        if(index>=list.length)
            index=0;
        return image.getImage();
    }
    
}

3.项目界面