//【例8.6】  圖像的動畫設計。

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import javax.swing.*;

public class ActiveImagesJApplet extends JApplet implements Runnable,ActionListener
{
    private Image[] images;                      //圖像數組
    private int index;                           //圖像數組下標

    private Thread athread;                      //線程
    private int sleeptime;                       //線程sleep時間

    private String graphfile;                    //圖像文件名
    private int graphcount;                      //圖像張數
    
    private JButton button_start,button_stop;    //啟動和停止按鈕
    
    public void init() 
    {
        this.index=0;
        this.athread=null;
        this.sleeptime = Integer.parseInt(this.getParameter("sleeptime")); //獲得參數
        this.graphfile = this.getParameter("graphfile");
        this.graphcount = Integer.parseInt(this.getParameter("graphcount"));
        this.images = new Image[this.graphcount];
        
        String fname = this.graphfile;
        int j = fname.indexOf(".");
        for (int i=0;i<this.graphcount;i++)      //所有圖像裝入數組
        {
            fname = fname.substring(0,j-1)+i+fname.substring(j);           //拼接其他圖像的文件名
            images[i] = this.getImage(this.getDocumentBase(),"Images/"+fname);
        }
        
        JPanel panel = new JPanel();
        button_start = new JButton("Start");
        panel.add(button_start);
        button_start.addActionListener(this);
        
        button_stop = new JButton("Stop");
        panel.add(button_stop);
        button_stop.addActionListener(this);

        this.setLayout(new BorderLayout());
        this.add(panel,"South");
    }
    
    public void update(Graphics g)
    {
        g.drawImage(this.images[this.index],0,0,this);
    }
    
    public void start() 
    {
        if (athread == null) 
        {
            athread = new Thread(this);
            athread.start();                     //線程啟動
            button_start.setEnabled(false);
            button_stop.setEnabled(true);
        }
    }
    
    public void stop() 
    {
        if (athread != null) 
        {
            athread.interrupt();                 //線程中斷
            athread = null;
            button_start.setEnabled(true);
            button_stop.setEnabled(false);
        }
    }
    
    public void run() 
    {
        while (true) 
        {
            index = (index+1) % images.length;   //下一幅圖像的下標
            repaint();
            try 
            {
                athread.sleep(this.sleeptime);
            }
            catch (InterruptedException e) 
            {                                    //中斷時拋出
                break;                           //退出循環
            }
        }
    }
    
    public void actionPerformed(ActionEvent e)
    {
        if (e.getSource()==button_start)         //單擊Start按鈕時
            this.start();                        //調用執行當前Applet對象的start()方法

        if (e.getSource()==button_stop)          //單擊Stop按鈕時
            this.stop();                         //調用執行當前Applet對象的stop()方法
    }
}