制作面板

package com.kaige123.paint;

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JColorChooser;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
*凯哥
*/
public class PaintJFrame extends JFrame implements ActionListener {

JButton jb1 = new JButton("线");
JButton jb2 = new JButton("矩形");
JButton jb3 = new JButton("圆");
JButton jb4 = new JButton("颜色");
JButton jb5 = new JButton("保存");
// 画笔的颜色是什么?
Color selectColor = Color.black;
// 绘画区域
MyJPanel jp = new MyJPanel(this);

public void actionPerformed(ActionEvent e) {
 
if (jb1 == e.getSource()) {
// 线
jp.setType("线");
} else if (jb2 == e.getSource()) {
// 矩形
jp.setType("矩形");
} else if (jb3 == e.getSource()) {
// 圆
jp.setType("圆");
} else if (jb4 == e.getSource()) {
// 颜色
// 这里弹出一个颜色的选择器 用他来选择颜色
JColorChooser jc = new JColorChooser();
// 打开颜色选择器 并得到颜色选择器选择的颜色
selectColor = jc.showDialog(this, "请选择颜色", selectColor);
// 把选好的颜色设置在按钮背景上
jb4.setBackground(selectColor);
} else if (jb5 == e.getSource()) {
// 保存
JFileChooser jf = new JFileChooser();
jf.showSaveDialog(this);
jp.save(jf.getSelectedFile());
}
}
  
// 构造器
public PaintJFrame() {

this.getContentPane().setBackground(Color.BLACK);
// 设置这个画板的底色 为白色
jp.setBackground(Color.white);
jp.setBounds(65, 10, 515, 550);
// 把绘画板 添加到窗口中
this.add(jp);
// 把按钮关联事件 注册事件
jb1.addActionListener(this);
jb2.addActionListener(this);
jb3.addActionListener(this);
jb4.addActionListener(this);
jb5.addActionListener(this);
// 设置按钮的位置
jb1.setBounds(1, 10, 60, 30);
jb2.setBounds(1, 40, 60, 30);
jb3.setBounds(1, 70, 60, 30);
jb4.setBounds(1, 100, 60, 30);
jb5.setBounds(1, 130, 60, 30);
// 添加按钮到窗口之中
this.add(jb1);
this.add(jb2);
this.add(jb3);
this.add(jb4);
this.add(jb5);
jb4.setBackground(selectColor);
// 没有布局 我们自己定义组件的摆放方式
this.setLayout(null);
// 设置窗口的标题 
this.setTitle("凯哥制作的画板 欢迎使用  www.kaige123.com ");
// 设置窗口的大小
this.setSize(600, 600);
// 显示窗口
this.setVisible(true); 
}

public static void main(String[] args) {
 
new PaintJFrame();
}

}

package com.kaige123.paint;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.Vector; 
import javax.imageio.ImageIO;
import javax.swing.JPanel;
/*
*凯哥
*/
//写一个类 去改造这个画板 
public class MyJPanel extends JPanel implements MouseListener {
 
public class Info {
String type = "";
int x;
int y;
int x1;
int y1;
Color c;
}
  
private PaintJFrame jf = null;
MyJPanel(PaintJFrame jf) {
this.jf = jf;
// 把事件关联到这个面板上 注册事件
this.addMouseListener(this);
}

private String type;
public void setType(String type) {
this.type = type;
}
  
int x, y;
// 鼠标的按下
public void mousePressed(MouseEvent e) {
x = e.getX();
y = e.getY();
}
  
Vector<Info> infos = new Vector<Info>();
  
public void paint(Graphics g) {
// 重绘
super.paint(g);
for (Info i : infos) {
g.setColor(i.c);
if (i.type.equalsIgnoreCase("线")) {
g.drawLine(i.x, i.y, i.x1, i.y1);
} else if (i.type.equalsIgnoreCase("矩形")) {
g.drawRect(i.x, i.y, i.x1, i.y1);
} else if (i.type.equalsIgnoreCase("圆")) {
g.drawOval(i.x, i.y, i.x1, i.y1);
}
}
}

public void save(File f) {
// 在内存中创建了一个照片
BufferedImage image = new BufferedImage(this.getWidth(),
this.getHeight(), BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();
// 给照片设置背景颜色
g.setColor(Color.white);
g.fillRect(0, 0, this.getWidth() + 1, this.getHeight() + 1);
for (Info i : infos) {
g.setColor(i.c);
if (i.type.equalsIgnoreCase("线")) {
  
g.drawLine(i.x, i.y, i.x1, i.y1);
  
} else if (i.type.equalsIgnoreCase("矩形")) {
  
g.drawRect(i.x, i.y, i.x1, i.y1);
  
} else if (i.type.equalsIgnoreCase("圆")) {
g.drawOval(i.x, i.y, i.x1, i.y1);
}
}
  
//捕获异常
try {
ImageIO.write(image, "jpeg", f);
} catch (Exception e) {
}
}

// 鼠标的松开
public void mouseReleased(MouseEvent e) {
int x1 = e.getX();
int y1 = e.getY();
Graphics2D g = (Graphics2D) this.getGraphics();
g.setColor(jf.selectColor);
Info info = new Info();
info.c = jf.selectColor;
info.type = type;
  
if (type.equalsIgnoreCase("线")) {
g.drawLine(x, y, x1, y1);
info.x = x;
info.y = y;
info.x1 = x1;
info.y1 = y1;
  
} else if (type.equalsIgnoreCase("矩形")) {
g.drawRect(x, y, x1 - x, y1 - y);
info.x = x;
info.y = y;
info.x1 = x1 - x;
info.y1 = y1 - y;
  
} else if (type.equalsIgnoreCase("圆")) {
g.drawOval(x, y, x1 - x, y1 - y);
info.x = x;
info.y = y;
info.x1 = x1 - x;
info.y1 = y1 - y;
}
  
infos.add(info);
}
public void mouseClicked(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e)  {}
}