drawimage.java

Demonstrate on how to draw image continuously by java applet

import java.util.*;
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[20];		//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=2;						//鸵鸟图像每次移动的距离
	int delay = 30;						//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;
	int imagenum=0;
	NumberMovie mov = new NumberMovie(); 
	Timer  timer;
	boolean Imageflag;
	public void init(){
		Imageflag=false;
		timer = new Timer();
		timer.schedule( mov, 1000, 1000 ); //设备定时器的运行时间
		tracker = new MediaTracker(this);
		/*for (int i=0;i<walkerImgs.length;i++){					//获取鸵鸟动作图像
			walkerImgs[i]=getImage(getCodeBase(),"recfile/av"+i+".jpg");
			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;
			timer.cancel();
		}
	}
    class NumberMovie extends TimerTask {
        public void run(){        
            System.out.println( "number"+ imagenum);  
        }
    }
	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=640;//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];
				if(Imageflag)
					walkerImgs[i]=getImage(getCodeBase(),"recfile/av"+i+".jpg");
				else
					walkerImgs[i]=getImage(getCodeBase(),"recfile/Sunset"+i+".jpg");
				System.out.println( "Imageflag"+ Imageflag);
				if(i == 19)
				{
					if(Imageflag)
						Imageflag = false;
					else
						Imageflag = true;
				}
				tracker.addImage(walkerImgs[i], 0);				//列入0组跟踪范围
				try{tracker.waitForID(0);}catch(InterruptedException e){return;	}
				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,0,0,this);
		imagenum++;
	}
	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);
		}							
	}
}