画板基本功能的实现（直线、矩形、椭圆的绘制；存储）
原始的画板：
(1)DrawUI类:
public class DrawUI extends javax.swing.JFrame{public static void main(String args[]){DrawUI ui = new DrawUI();ui.initDrawUI();}/** * 初始化窗体的方法 */public void initDrawUI(){//指调用房当前initDrawUI()方法的对象this.setTitle("我的画板v01");this.setSize(600,500);//设置布局java.awt.FlowLayout fl = new java.awt.FlowLayout();this.setLayout(fl);//创建一个按钮组javax.swing.ButtonGroup group = new javax.swing.ButtonGroup();//单选按钮javax.swing.JRadioButton line = new javax.swing.JRadioButton("直线");//设置按钮的动作命令line.setActionCommand("line");//默认选中直线line.setSelected(true);javax.swing.JRadioButton rect = new javax.swing.JRadioButton("矩形");rect.setActionCommand("rect");javax.swing.JRadioButton oval = new javax.swing.JRadioButton("椭圆");oval.setActionCommand("oval");//按钮分组group.add(line);group.add(rect);group.add(oval);this.add(line);this.add(rect);this.add(oval);this.setDefaultCloseOperation(3);this.setVisible(true);//从窗体上获取画布//窗体在屏幕上所占据的区域是允许改变颜色的java.awt.Graphics g = this.getGraphics();//创建一个鼠标监听器对象DrawListener dlis = new DrawListener(g,group);//给窗体加鼠标监听器this.addMouseListener(dlis);}}?(2)DrawListener类：
import java.awt.event.MouseEvent;/** * 画板的监听器，实现鼠标监听器接口 * * @author Administrator * */public class DrawListener implements java.awt.event.MouseListener {private int x1, y1, x2, y2;private java.awt.Graphics g;private javax.swing.ButtonGroup group;private String type = "line";public DrawListener(java.awt.Graphics g, javax.swing.ButtonGroup group) {this.g = g;this.group = group;}// 按下public void mousePressed(MouseEvent e) {// 先判断要绘制的形状// 得到选中选项的动作命令type = group.getSelection().getActionCommand();System.out.println("要绘制的形状："+type);// 得到鼠标按下时候光标的坐标x1 = e.getX();y1 = e.getY();}// 释放public void mouseReleased(MouseEvent e) {// 得到鼠标释放时候光标的坐标x2 = e.getX();y2 = e.getY();if ("line".equals(type)) {// 当鼠标释放的时候就画直线g.drawLine(x1, y1, x2, y2);} else if (type.equals("rect")) {g.drawRect(x1, y1, x2 - x1, y2 - y1);} else if (type.equals("oval")) {g.drawOval(x1, y1, x2 - x1, y2 - y1);}}// 进入public void mouseEntered(MouseEvent e) {// System.out.println("mouseEntered");}// 离开public void mouseExited(MouseEvent e) {// System.out.println("mouseExited");}// 点击public void mouseClicked(MouseEvent e) {// System.out.println("mouseClicked");}}?
总结：
1、运用initDraw()设计窗体，而非把所有设计步骤都放在main()方法中
2、设计窗体的框架步骤：a、大小、标题->布局->添加元素组件->关闭操作、可见性
?????????????????????????????????? b、为窗体添加监听器
3、只有组件可见后方可创建Graphics对象
4、单选按钮需添加进按钮组方可起作用
5、运用属性、构造函数将两个相关类连接起来（例如：将属性Graphics g,Buttongroup group传入DrawListener类）
6、Graphics类不能使用构造方法来创建对象
7、每个按钮都有其动作命令（和按钮的文本不一样）
8、只要为组件添加监听器，组件就可以自动监听动作事项
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扩展后的画板（任意方向画图、存储数据）：
（1）接口Shape;实现类Line、Rect、Oval
import java.awt.Color;import java.awt.Graphics;public abstract class Shape {//坐标、颜色 protected int x1,x2,y1,y2; protected Color color; //draw()方法 public abstract void draw(Graphics g); }?
import java.awt.Graphics;import java.awt.Color;public class Line extends Shape{//重写构造方法public Line(int x1,int y1,int x2,int y2,Color color){this.x1=x1;this.y1=y1;this.x2=x2;this.y2=y2;this.color=color;}//重写draw()方法 public void draw(Graphics g){ g.setColor(color); g.drawLine(x1,y1,x2,y2); }}?
import java.awt.Graphics;import java.awt.Color;public class Rect extends Shape{public Rect(int x1,int y1,int x2,int y2,Color color){this.x1=x1;this.y1=y1;this.x2=x2;this.y2=y2;this.color=color;}public void draw(Graphics g){g.setColor(color);g.drawRect(Math.min(x1,x2),Math.min(y1,y2),Math.abs(x2-x1),Math.abs(y2-y1));}}?
import java.awt.Color;import java.awt.Graphics;public class Oval extends Shape{public Oval(int x1,int y1,int x2,int y2,Color color){this.x1=x1;this.y1=y1;this.x2=x2;this.y2=y2;this.color=color;}public void draw(Graphics g){g.setColor(color);g.drawOval(Math.min(x1,x2),Math.min(y1, y2),Math.abs(x2-x1),Math.abs(y2-y1));}}?
(2)DrawUI、DrawListener类
public class DrawUI extends javax.swing.JFrame{public static void main(String args[]){DrawUI ui = new DrawUI();ui.initDrawUI();}/** * 初始化窗体的方法 */public void initDrawUI(){//指调用房当前initDrawUI()方法的对象this.setTitle("我的画板v01");this.setSize(600,500);//设置布局java.awt.FlowLayout fl = new java.awt.FlowLayout();this.setLayout(fl);//创建一个按钮组javax.swing.ButtonGroup group = new javax.swing.ButtonGroup();//单选按钮javax.swing.JRadioButton line = new javax.swing.JRadioButton("直线");//设置按钮的动作命令line.setActionCommand("line");//默认选中直线line.setSelected(true);javax.swing.JRadioButton rect = new javax.swing.JRadioButton("矩形");rect.setActionCommand("rect");javax.swing.JRadioButton oval = new javax.swing.JRadioButton("椭圆");oval.setActionCommand("oval");//按钮分组group.add(line);group.add(rect);group.add(oval);this.add(line);this.add(rect);this.add(oval);this.setDefaultCloseOperation(3);this.setVisible(true);//从窗体上获取画布//窗体在屏幕上所占据的区域是允许改变颜色的java.awt.Graphics g = this.getGraphics();//创建一个鼠标监听器对象DrawListener dlis = new DrawListener(g,group);//给窗体加鼠标监听器this.addMouseListener(dlis);}}?
import java.awt.event.MouseEvent;/** * 画板的监听器，实现鼠标监听器接口 * * @author Administrator * */public class DrawListener implements java.awt.event.MouseListener {private int x1, y1, x2, y2;private java.awt.Graphics g;private javax.swing.ButtonGroup group;private String type = "line";public DrawListener(java.awt.Graphics g, javax.swing.ButtonGroup group) {this.g = g;this.group = group;}// 按下public void mousePressed(MouseEvent e) {// 先判断要绘制的形状// 得到选中选项的动作命令type = group.getSelection().getActionCommand();System.out.println("要绘制的形状："+type);// 得到鼠标按下时候光标的坐标x1 = e.getX();y1 = e.getY();}// 释放public void mouseReleased(MouseEvent e) {// 得到鼠标释放时候光标的坐标x2 = e.getX();y2 = e.getY();if ("line".equals(type)) {// 当鼠标释放的时候就画直线g.drawLine(x1, y1, x2, y2);} else if (type.equals("rect")) {g.drawRect(x1, y1, x2 - x1, y2 - y1);} else if (type.equals("oval")) {g.drawOval(x1, y1, x2 - x1, y2 - y1);}}// 进入public void mouseEntered(MouseEvent e) {// System.out.println("mouseEntered");}// 离开public void mouseExited(MouseEvent e) {// System.out.println("mouseExited");}// 点击public void mouseClicked(MouseEvent e) {// System.out.println("mouseClicked");}}?对比总结：
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1、将Line、Rect、Oval分别创建成类，实现Shape接口，便于统一规范存储?
2、因为存储元素（对象）个数不固定，故选择队列存储方式
3、每个对象所要存储的数据变量以属性表示
4、接口以实现程序的目标为准，将各个实现类的共有属性和方法加以归纳提炼
5、运用接口可以灵活使用累的多态性这一特征
6、运用构造函数将一个类中的属性传入另一个类?