Java动画短片当不移动鼠标光标时

这个程序在某些系统上显示出一个奇怪的行为.在带有nVidia卡的电脑上,它运行顺利.在我的Vaio笔记本上,在一个BeagleBoneBlack和一个朋友的Mac上,它沉重地放下.看起来暂停一段时间,然后向左移动约10个像素,再次暂停等等.

什么困扰我的事实是,在这些系统上,如果您没有触摸鼠标,动画只会停留.只要您将鼠标光标移动到窗口内,无论多么缓慢,或者拖动窗口本身,动画运行顺利！

有人可以解释一下吗这是程序：

import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
import java.util.*;

class Textimg extends JComponent
{
    String      str;
    Font        font;
    int         x = 0;
    final int   ytext = 136;
    Image       img;

    public Textimg(String s)
    {
        str = s;
        font = new Font("Noserif",Font.PLAIN,96);
        setLayout(null);
    }

    protected void paintComponent(Graphics g)
    {
        if (img == null)
        {
            img = createImage(4800,272);
            Graphics gr = img.getGraphics();

            gr.setFont(font);
            gr.setColor(Color.BLACK);
            gr.fillRect(0,4800,272);
            gr.setColor(new Color(135,175,0));
            gr.drawString(str,ytext);
            gr.dispose();
        }

        g.drawImage(img,x,this);
    }

    public void addX(int dif)
    {
        if (isVisible())
        {
            x = x + dif;

            Graphics g = getGraphics();

            if (g != null) paintComponent(g);
        }
    }
} 


public class Banner extends JFrame 
{ 
    StringBuffer    buf;
    int             sleeptime = 10;

    Banner(String path) throws IOException 
    { 
        setSize(new Dimension(480,272));
        setTitle("Java Test");
        setDefaultCloSEOperation(EXIT_ON_CLOSE);
        setLayout(null);

        BufferedReader reader = new BufferedReader(
                new InputStreamReader(new FileInputStream(path),"UTF-8"));

        buf = new StringBuffer();

        while (true) 
        {
           String line = reader.readLine();

           if (line == null) break;
           buf.append(line);
        }

        final Textimg textimg = new Textimg(buf.toString());

        add(textimg);
        textimg.setBounds(0,480,272);

        final javax.swing.Timer timer = new javax.swing.Timer(200,new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                textimg.addX(-1);
            }
        });

        timer.setDelay(sleeptime);
        timer.start();
    }

    //----------------------------------------------------------------------

    public static void main(String[] args) throws Exception
    {
        new Banner(args[0]).setVisible(true);
    }
}