walker.java

介绍有关java的资料 课件 相当一本书籍 里面都是很基础的知识

/**
 * Title:        Java语言多媒体编程演示
 * Description:  Java语言多媒体编程演示，用于北京师范大学计算机系Java课程教学示范。
 * Copyright:    Copyright (c) 2001
 * Company:      北京师范大学计算机系
 * @author 孙一林
 * @version 1.0
 */

import java.awt.MediaTracker;
import java.awt.Graphics;
import java.awt.Image;
//import java.applet.AudioClip;

public class Walker extends java.applet.Applet implements Runnable{
	Image offScreenImg;					//存放备用屏幕的内容
	Graphics offScreenG;					//备用屏幕的绘图环境
	MediaTracker tracker;					//媒体跟踪器
	Image walkerImgs[]=new Image[5];		//存放鸵鸟走路姿势图像
	Image currentImg;						//当前放映的鸵鸟动作图像
	int xpos,ypos=0;						//鸵鸟动作图像显示的位置
	int walk_step=20;						//鸵鸟图像每次移动的距离
	int delay = 250;						//每帧时延（毫秒）
	Thread runThread;
	Image bgImage;						//存放草原背景图像
	int applet_width,applet_height;
	int birdImg_width;						//鸵鸟图像宽度
	//AudioClip bgmusic;

	public void init(){
		tracker = new MediaTracker(this);
		for (int i=0;i<walkerImgs.length;i++){					//获取鸵鸟动作图像
			walkerImgs[i]=getImage(getCodeBase(),"images/bird"+i+".gif");
			tracker.addImage(walkerImgs[i], 0);				//列入0组跟踪范围
		}
		bgImage = getImage(getCodeBase(),"images/"+"bg.gif");	//获取草原背景图像
		tracker.addImage(bgImage, 0);						//列入0组跟踪范围
		//bgmusic=getAudioClip(getDocumentBase(),"space.au");	//获取背景音乐
		applet_width=size().width;
		applet_height=size().height;
		try {
			offScreenImg = createImage (applet_width,applet_height);//创建备用屏幕
			offScreenG = offScreenImg.getGraphics ();//获取备用屏幕的绘图环境
		}
		catch (Exception e) {
			offScreenG = null;		//若出错，就置备用屏幕的绘图上下文环境为null
		}
	}
/*
       public boolean mouseMove(java.awt.Event evt, int x, int y) {
          ypos = y;                                   // 获取鼠标Y方向的值
	  return true;
      }
*/
	public void start (){
		if (runThread==null){
			runThread=new Thread(this);
			runThread.start();
		}
	}

	public void stop(){
		if (runThread!=null){
			//if(bgmusic!=null)
			//	bgmusic.stop();
			runThread.stop();
			runThread=null;
		}
	}

	public void run(){
		try{
			tracker.waitForID(0);			//等待0组中所有图像的到达
		}catch(InterruptedException e){
			return;
		}
		//if(bgmusic!=null)
		//	bgmusic.loop();
		birdImg_width=walkerImgs[0].getWidth(this);
		int i=0;
		while(true){
			for(xpos=-birdImg_width;xpos<=applet_width;xpos+=walk_step){//计算位置
         			currentImg=walkerImgs[i];
				repaint();
				i=(i+1)%walkerImgs.length;			//计算下一帧是哪幅图像
				try{Thread.sleep(delay);}
				catch(InterruptedException e){}
			}
		}
	}

	public void paint(Graphics g){
		g.drawImage(bgImage,0,0,this);
		g.drawImage(currentImg,xpos,ypos,this);
	}
	public void update(Graphics g){
		if (offScreenG!=null) {					//如果备用屏幕创建成功
			paint(offScreenG);
			g.drawImage(offScreenImg,0,0,this);	//将备用屏幕内容画到当前屏幕来
		}
		else
			paint(g);
	}
}