//单件模式，用来储存截图的缓冲区。
    private static Vector bufferVec = null;
    //标识缓冲区是否储存固定数目的截图，默认为固定数目。
    private boolean isLimitedBuffer = true;
    //伪视频所覆盖的自动测试过程，单位为秒；默认情况下存储最近30秒内的截图。
    private int videoLength = 30;  
    //截图的时间间隔，单位为秒；默认情况下每隔1秒执行一次抓屏操作。
    private double snapInterval = 1;  
    //缓冲区容量，该属性值由videoLength和snapInterval共同决定。
    private int bufferCapability;
    //伪视频输出位置
    private String outputLocation = "c:/";
    //伪视频格式，即生成的动态图片格式，在本例给出的实现使用了GIF格式。
    private String pseudoVideoFormat = ".gif";
    //标识生成的伪视频是否循环播放，默认为只播放一次。
    private boolean replayIndefinitely = false;
    //伪视频的重放速度，可选值为1，2，3。分别表示快速、中速和慢速。
    private int replaySpeed = 2;
    //标识是否有错误发生。当其值为true时，表明需要立即生成伪视频。
    public static boolean errorFlag = false;

/**
 * Create a screenshot pool with limited capability, it only 
 * stores enough screenshots to create a pseudo-video of appointed length
 * 
 * @param videoLength - length of pseudo-video
 * @param snapInterval - interval to scratch screenshots, the unit is second
 * @param replayIndefinitely - the video plays once or repeats indefinitely
 * @param replaySpeed - play speed of the video,1 means fast,2 is normal,and 3 means slow
 */
    public ScreenshotsPool(int videoLength, double snapInterval, 
                           boolean replayIndefinitely, int replaySpeed) {
        super();
        this.isLimitedBuffer = true;
        this.videoLength = videoLength;
        this.snapInterval = snapInterval;
        this.replayIndefinitely = replayIndefinitely;
        //设置有效的回放速度；
        if((replaySpeed==1)||(replaySpeed==2)||(replaySpeed==3))
            this.replaySpeed = replaySpeed;
        //通过伪视频长度videoLength和抓屏频率snapInterval计算出缓冲区的容量
        this.bufferCapability = new Double(videoLength/snapInterval).intValue();
        //初始化缓冲区
        getBufferVec();
    }
    

/**
 * Get buffer pool that store screenshots
 * 
 * @return Vector - the only buffer pool to store screenshots
 */
    public Vector getBufferVec()
    {
        if(null==bufferVec)
            bufferVec = new Vector(bufferCapability);
        return bufferVec;
    }

/**
 *  Push a new screenshot into buffer
 *  if the buffer is limited and has reached its capability, the oldest
 *  snapshot would be removed
 */
    public void pushScreenshot()
    {
    //获得当前屏幕的截图对象
        BufferedImage image = getCurrentScreen();
        if(null==image)
            return;
         //如果截图缓冲区有固定容量，
        if(isLimitedBuffer){
            //如果已经到达缓冲区的最大容量，则删去第一副截图
            int size = getBufferVec().size();
            if(size==bufferCapability)
                getBufferVec().remove(0);
        }
        //将当前截图存入缓冲区
        getBufferVec().add(image);

    }

/**
 *  Get current screenshot
 * 
 * @return BufferedImage - screenshot of current screen
 */
    public BufferedImage getCurrentScreen()
    {
    try{
            //获得屏幕大小
            Dimension screenSize = toolkit.getDefaultToolkit().getScreenSize();
            int width = screenSize.width;
            int height = screenSize.height;
            BufferedImage capture = null;
            //获得当前屏幕范围
            Rectangle area = new Rectangle(0, 0, width, height);
            Robot robot = new Robot();
            //截取当前屏幕范围内的内容，返回BufferedImage对象
            capture = robot.createScreenCapture(area);
            return capture;
        }
        catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

/**
 * Generate pseudo-video with those buffered screens in pool
 * 
 * Here we will generate animated picture of '.gif' format, and we can
 * generate animated picture of other formats likewise.(SVG, PNG, etc.)
 */
    public void generatePseudoVideo()
    {
        int size = this.getBufferVec().size();
        if(size<1)
            return;  
        try{ 			
            BufferedImage bi = null;
            //新建一个AnimatedGifEncoder对象，用来生成动态的GIF文件
            AnimatedGifEncoder pseudoVideoGenerator = new AnimatedGifEncoder(); 
            //设置GIF文件是否循环显示各帧
            int repeat = replayIndefinitely?0:1;
            pseudoVideoGenerator.setRepeat(repeat); 
            //设置输出位置，以当前时间为文件名
           pseudoVideoGenerator.start(outputLocation+getCurrentTime()+pseudoVideoFormat);
            //依次将缓冲区内的所有截图按指定间隔加入AnimatedGifEncoder对象
            for(int i=0;i

/**
 * main method of this thread
 */
    public void run()
    {
        while(true) 
        { 
            try 
            { 				 
                //将当前屏幕的截图存入缓冲区
                pushScreenshot();
                //睡眠一段时间
                Thread.sleep(new Double(1000*this.snapInterval).longValue());
                //查看错误标识，一旦有错
                if(errorFlag)
                { 		
                    //立即生成伪视频			
                    generatePseudoVideo();
                    //复位错误标识
                    errorFlag = false; 				
                }
            }
            catch(Exception e) 
            { 
                e.printStackTrace();
            }
        }

    }