import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ProgressBarDemo extends JPanel
                             implements ActionListener {
    public final static int ONE_SECOND = 1000;
    private JProgressBar progressBar;
    private Timer timer;
    private JButton startButton;
    private LongTask task;
   
    public ProgressBarDemo() {
        super(new BorderLayout());
        task = new LongTask();
        //創建用戶界面
        startButton = new JButton("開始");
        startButton.addActionListener(this);

        progressBar = new JProgressBar(0, task.getLengthOfTask());
        progressBar.setValue(0);
        progressBar.setStringPainted(true);
        JPanel panel = new JPanel();
        panel.add(startButton);
        panel.add(progressBar);
        add(panel, BorderLayout.CENTER);
        //創建定時器
        timer = new Timer(ONE_SECOND, new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                progressBar.setValue(task.getCurrent());              
                if (task.isDone()) {
                    Toolkit.getDefaultToolkit().beep();
                    timer.stop();
                    startButton.setEnabled(true);
                    setCursor(null); //關閉等待光標
                    progressBar.setValue(progressBar.getMinimum());
                }
            }
        });
    }   /*當按下開始按鈕時開始調用*/
    public void actionPerformed(ActionEvent evt) {
        startButton.setEnabled(false);
        setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
        task.go();   timer.start();
    }   /*創建用戶窗口.為了線程安全,這個方法應該被事件處理線程調用*/
    private static void createAndShowGUI() {
        JFrame frame = new JFrame("進度條示例");//創建和設置窗口
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //創建和設置內容框
        JComponent newContentPane = new ProgressBarDemo();
        newContentPane.setOpaque(true); //應試是不透明的。
        frame.setContentPane(newContentPane);
        frame.pack();    //顯示窗口
        frame.setVisible(true);
    }
    public static void main(String[] args) {
    	//創建和顯示程序的用戶界面,為事件處理線程提供事件
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() { createAndShowGUI();}
        });
    }
}
class LongTask {
    private int lengthOfTask;
    private int current = 0;
    private boolean done = false;
    private boolean canceled = false;
    public LongTask() {   //計算進度
        lengthOfTask = 1000;
    }      /*開始任務*/
    public void go() {
        final SwingWorker worker = new SwingWorker() {
            public Object construct() {
                current = 0;  done = false;
                canceled = false;      
                return new ActualTask();
            }
        };
        worker.start();
    }   /*查看有多少任務需要去做*/
    public int getLengthOfTask() { return lengthOfTask; }
    /*查看完成的多少*/
    public int getCurrent() {  return current; }
    public void stop() {  canceled = true;  }
    /*被ProgressBarDemo調用,查看任務是否完成*/
    public boolean isDone() {   return done;}
 /*返回最新狀態信息,如果沒有返回null*實在的常運行任務,在SwingWorker中運行*/
    class ActualTask {
        ActualTask() {  //創建隨機數量的進度
            while (!canceled && !done) {
                try {
                    Thread.sleep(1000); //掛起一秒
                    current += Math.random() * 100; //做進度條
                    if (current >= lengthOfTask) {
                        done = true;
                        current = lengthOfTask;
                    }
                } catch (InterruptedException e) {
                    System.out.println("ActualTask interrupted");
                }
            }
        }
    }
}
abstract class SwingWorker {
    private Object value;  // 看 getValue(), 看 Value()
    /*在分開的同步控制下維持worker線程的引用*/
    private static class ThreadVar {
        private Thread thread;
        ThreadVar(Thread t) { thread = t; }
        synchronized Thread get() { return thread; }
        synchronized void clear() { thread = null; }
    }
    private ThreadVar threadVar;
    /*取得worker產生的值,如果還沒有創建返回null*/
    protected synchronized Object getValue() { 
        return value; 
    }/*設置worker線程產生的值*/
    private synchronized void setValue(Object x) { 
        value = x; 
    }    /*計算返回值*/
    public abstract Object construct();
    /*構造光方法返回后,調用事件發送線程*/
    public void finished() {   }
    /*新方法,打斷現在工作線程,而不管他在做什么.*/
    public void interrupt() {
        Thread t = threadVar.get();
        if (t != null) {  t.interrupt(); }
        threadVar.clear();
    }   /*返回構造函數的值,如果被中斷返回null*/
    public Object get() {
        while (true) {  
            Thread t = threadVar.get();
            if (t == null) {   return getValue();}
            try    { t.join();}
            catch (InterruptedException e) {
                Thread.currentThread().interrupt(); //宣傳
                return null;
            }
        }
    }   /*調用構造函數,然后退出*/
    public SwingWorker() {
        final Runnable doFinished = new Runnable() {
           public void run() { finished(); }
        };
        Runnable doConstruct = new Runnable() { 
            public void run() {
                try  {setValue(construct());}
                finally   { threadVar.clear();}
                SwingUtilities.invokeLater(doFinished);
            }
        };
        Thread t = new Thread(doConstruct);
        threadVar = new ThreadVar(t);
    }    /*開始worker線程*/
    public void start() {
        Thread t = threadVar.get();
        if (t != null)   { t.start();}
    }
}