利用小项目加深面向对象的思想---2.太阳系轨迹图

1.创建包和图片管理

2.cn.bjsxt.util包里面是台球反弹代码（可看昨天发的小项目）

Constant.java

package cn.bjsxt.util;

/**
 * 游戏项目中用到的常量
 * @author dell
 *
 */
public class Constant {
	public static final int GAME_WIDTH = 900;
	public static final int GAME_HEIGHT =700;
	
}

GameUtil.java

package cn.bjsxt.util;

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;

/**
 * 游戏开发的工具类（加载图片）
 * @author Administrator
 *
 */

public class GameUtil {
	public static Image getImage(String  path){
		URL u=GameUtil.class.getClassLoader().getResource(path);
		BufferedImage img=null;
		try {
			img=ImageIO.read(u);
		}catch (IOException e) {
			e.printStackTrace();
		}
		return img;
	}
	
}

MyFrame.java

package cn.bjsxt.util;
import java.awt.Frame;
import java.awt.Image;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class MyFrame extends Frame {
	/**
	 * 加载窗口
	 */
	public void launchFrame(){
		 setTitle("太阳系运行轨迹图");
		setSize(Constant.GAME_WIDTH,Constant.GAME_HEIGHT);
		setLocation(100, 100);
		setVisible(true);
		
		new PaintThread().start();  //启动重画线程
		
		addWindowListener(new WindowAdapter() {
			@Override
			public void windowClosing(WindowEvent e){
				System.exit(0);
			}
			
		});
	}
class PaintThread extends Thread {
		
		public void run(){
			while(true){
				repaint();
				try {
					Thread.sleep(100); //1s = 1000ms
				} catch (InterruptedException e) {
					e.printStackTrace();
				}   
			}
		}
		
	}
}

此包下的三个方法，主要是构建界面，加载图片和增加线程使其有动画效果。

3.cn.bjsxt.solar包下

  Star.java

package cn.bjsxt.solar;

import java.awt.Graphics;
import java.awt.Image;
import cn.bjsxt.util.GameUtil;
public class Star {
	Image img;
	double x,y;
	int width,height;
	
	public void draw(Graphics g) {
		g.drawImage(img, (int)x,(int)y,null);
	}
	public Star(Image img){
		this.img=img;
		this.width=img.getWidth(null);
		this.height=img.getHeight(null);
		
	}
	public Star() {
		
	}
	public Star(Image img,double x,double y){
		this(img);
		this.x = x;
		this.y = y;
		
		
	}
  public Star(String imgpath,double x,double y) {
	    this(GameUtil.getImage(imgpath),x,y);
  }
}

此代码定义几个构造方法，重载SolarFrame.java中只有一处调用此代码

Star sun=new Star("images/sun.jpg",Constant.GAME_WIDTH/2,Constant.GAME_HEIGHT/2);

定义一个不动的太阳，传入参数后，通过此来调用别的构造方法，后sun.draw（g），调用g.drawImage（img，（int）x，（int）y，null）;来绘制太阳图像。

 

Planet.java

package cn.bjsxt.solar;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import cn.bjsxt.util.GameUtil;

public class Planet extends Star{	
	//除了图片，行星沿着某个椭圆运行：长轴、短轴、速度、角度。 绕着某个Star飞。
	double longAxis;    //椭圆的长轴
	double shortAxis;   //椭圆的短轴
	double speed;       //飞行的速度
	double degree;     //角度
	Star center;
	boolean satellite;  //是否画线，主要还是月亮运作没有画线
	
	public void draw(Graphics g) {
		super.draw(g);
		move();
		if(!satellite) {    //判读是否画椭圆线，主要是月亮没画
			drawTrace(g);
		}
	}
	public void drawTrace(Graphics g) {
		double ovalX,ovalY,ovalWidth,ovalHeight;
		ovalWidth=longAxis*2;
		ovalHeight=shortAxis*2;
		ovalX=center.x+center.width/2-longAxis;
		ovalY=center.y+center.height/2-shortAxis;
		
	   Color c=g.getColor();
		g.setColor(Color.blue);
		g.drawOval((int)ovalX, (int)ovalY,(int)ovalWidth,(int)ovalHeight);
		g.setColor(c);
	}
	  public void move() {
		//沿着椭圆飞行
		 x=center.x+center.width/2-img.getWidth(null)/2+longAxis*Math.cos(degree);
	     y=center.y+center.height/2-img.getHeight(null)/2+shortAxis*Math.sin(degree);
			degree+=speed;
	  }
	
	public Planet(Star center,String imgpath, double longAxis,
			double shortAxis, double speed) {
		super(GameUtil.getImage(imgpath));
		this.center = center;
	     this.x=center.x+longAxis;
	     this.y=center.y;
		this.longAxis = longAxis;
		this.shortAxis = shortAxis;
		this.speed = speed;
		this.width=img.getWidth(null);
		this.height=img.getHeight(null);
		
	}
	
	public Planet(Star center,String imgpath, double longAxis,
			double shortAxis, double speed,boolean satellite) {
	  this(center, imgpath, longAxis, shortAxis, speed);
	  this.satellite=satellite;
	}
	
	public Planet(Image img, double x, double y) {
		super(img, x, y);
	}
	public Planet(String imgpath, double x, double y) {
		super(imgpath, x, y);		
	}

}

此代码，继承Star.java，Star.java，主要还是绘制太阳，是静态的，我们通过继承Star.java来实现行星椭圆动态旋转

drawTrace（Graphics g）绘画椭圆线

移动（），绘制行星移动

SolarFrame.java

package cn.bjsxt.solar;

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

import cn.bjsxt.util.Constant;
import cn.bjsxt.util.GameUtil;
import cn.bjsxt.util.MyFrame;

public class SolarFrame extends MyFrame{
    private Image iBuffer;
	private Graphics gBuffer;
	Image bg=GameUtil.getImage("images/bg.jpg");
	//Star bg=new Star("images/bg.jpg",0,0);
	Star sun=new Star("images/sun.jpg",Constant.GAME_WIDTH/2,Constant.GAME_HEIGHT/2);
	
	  Planet mercury=new Planet(sun,"images/Mercury.jpg", 80,50,0.08);
	  Planet venus=new Planet(sun,"images/Venus.jpg", 110,70,0.07);
	  Planet earch=new Planet(sun,"images/earth.jpg", 145,95,0.06);
	  Planet moon=new Planet(earch,"images/moon.jpg", 20,15,0.5,true);
	  Planet mars=new Planet(sun,"images/Mars.jpg", 185,125,0.05);
	  Planet jupier=new Planet(sun,"images/Jupiter.jpg",230,160,0.04);
	  Planet saturn=new Planet(sun,"images/Saturn.jpg", 280,200,0.03);
	  Planet uranus=new Planet(sun,"images/Uranus.jpg", 335,245,0.02);
	  Planet neptune=new Planet(sun,"images/Neptune.jpg",395,295,0.01);
	
	
	  
	
	  public void paint(Graphics g) {
		g.drawImage(bg, 0, 0, null);
		 //bg.draw(g);
		  sun.draw(g);
		  mercury.draw(g);
		  venus.draw(g);
		  earch.draw(g);
		  moon.draw(g);
		  mars.draw(g);
		  jupier.draw(g);
		  saturn.draw(g);
		  uranus.draw(g);
		  neptune.draw(g);
	  }
	    public void update(Graphics scr)
		{
		    if(iBuffer==null)
		    {
		       iBuffer=createImage(this.getSize().width,this.getSize().height);
		       gBuffer=iBuffer.getGraphics();
		    }
		       gBuffer.setColor(getBackground());
		       gBuffer.fillRect(0,0,this.getSize().width,this.getSize().height);
		       paint(gBuffer);
		       scr.drawImage(iBuffer,0,0,this);
		}
	  public static void main(String[] args) {
		new SolarFrame().launchFrame();
	}
}

此代码为调用   

注意：  在Java编写具有连贯变化的窗口程序时，通常的办法是在子类中覆盖父类的paint(Graphics)方法，在方法中使用实现窗口重绘的过程。连贯变换的窗口会不断地调用update(Graphics)函数，该函数自动的调用paint(Graphics)函数。这样就会出现闪烁的情况。为了解决这一问题，可以应用双缓冲技术。可以通过截取上述过程，覆盖update(Graphics)函数，在内存中创建一个与窗口大小相同的图形，并获得该图形的图形上下文(Graphics)，再将图片的图形上下文作为参数调用paint(Graphics)函数（paint(Graphics)中的GUI函数会在图片上画图），再在update(Graphics)函数调用drawImage函数将创建的图形直接画在窗口上。
 

 

总结：此小项目很简单，里面用到重载，这个调用和继承关系，其实这些东西很容易理解，但写项目就不知道怎么构架，非常适合新手，而现在我也是新手，好长时间没学的java了。