【138天】尚学堂高淇Java300集视频精华笔记（84）

第84集：太阳系模型/基本类的封装/Star类的创建

本集知识点

1. 将对象尽量的抽象，能够有效减小代码量，好比此例中的Star类

   package com.test084_087_solar;
   
   import java.awt.Graphics;
   import java.awt.Image;
   
   import com.test084_087_util.GameUtil;
   
   public class Star {
       Image img;
       double x,y;
       
       public void draw(Graphics g){
           g.drawImage(img,(int)x,(int)y,null);
       }
       
       public Star(Image img,double x,double y){
           this.img = img;
           this.x = x;
           this.y = y;
       }
       
       public Star(String imgpath,double x,double y){
           this.img = GameUtil.getImage(imgpath);
           this.x = x;
           this.y = y;
       }
       
   }

2. 构建常量类的好处相似CSS，改一个地方，其它地方都改了，例如此例中的Constant.GAME_WIDTH。

   package com.test084_087_util;
   
   /**
    * @author wangtao
    *    游戏项目中用到的常量
    */
   public class Constant {
       public static final int GAME_WIDTH = 800;
       public static final int GAME_HEIGHT = 600;
       
   }

3. paint会在对象加载时自动调用。

   package com.test084_087_solar;
       
       import java.awt.Graphics;
       import java.awt.Image;
       
       import com.test084_087_util.Constant;
       import com.test084_087_util.GameUtil;
       import com.test084_087_util.MyFrame;
       
       public class SolarFrame extends MyFrame {
           Image bg = GameUtil.getImage("images/bg.jpg");
           Star sun = new Star("images/sun.jpg",Constant.GAME_WIDTH/2,Constant.GAME_HEIGHT/2);
           
           
           public void paint(Graphics g){
               g.drawImage(bg,0,0,null);
               sun.draw(g);
           }
           
           public static void main(String[] args){
                new SolarFrame().launchFrame();
           }
       }