这是一个经典的错误：您正在阻止EDT（Event Dispatching Thread）循环遍历 Thread.sleep（）。 EDT分派所有GUI事件：绘画事件，鼠标事件，按键事件，动作事件等...由于您在EDT中循环和休眠（在ActionEvent期间），它会阻止显示刷新（我下注点击按钮后，图形用户界面变得没有响应）。所以

• 规则＃1：不要阻止EDT


• 规则＃2：不要阻塞美国东部时间，直接导致


• 规则＃3：EDT中不 sleep（），
$规则4：不要在EDT中执行任何冗长的操作要解决此问题，请使用 SwingWorker 或 javax.swing.Timer 。这也可以与传统的 Thread 的和 Executors （线程池）一起工作，但是你必须确保所有的您尝试修改GUI在EDT中执行。

您可能需要查看这个例子 a>，它显示了如何组合JProgressBar和SwingWorker

In the following application I have put a button ,clicking on which makes the GlassPane visible and a Thread starts which updates the Progress bar value.Below is the code:-

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.LinearGradientPaint;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;


public class GlassPaneDownload extends JFrame implements Runnable{
Thread t;
CustomGlassPane jp;

public static void main(String args[])
{
SwingUtilities.invokeLater(new Runnable(){public void run(){new GlassPaneDownload();}});
}

public GlassPaneDownload(){
super("Glass Pane Download Simulation");
setSize(400,400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new FlowLayout());    

jp=new CustomGlassPane();

jp.setOpaque(false);
setGlassPane(jp);


JButton btn=new JButton("Click Here");
btn.addActionListener(new ActionListener(){public void actionPerformed(ActionEvent e){
    //Make Glass Pane visible
    jp.setVisible(true);
    //Start Thread to update Progress Bar
    t=new Thread();
    t.start();
}});
add(btn);
setVisible(true);
}
public void run(){
for(int i=1;i<=100;i++)
{
    jp.setProgress(i);
    try {
        Thread.sleep(100);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
t=null;
}
}

class CustomGlassPane extends JComponent
{


    private final float pattern[]=new float[]{0.0f,0.499f,0.50f,1.0f};
    private final Color color[]=new Color[]{Color.WHITE,Color.GRAY,Color.BLACK,Color.LIGHT_GRAY};
    private int progress,oldProgress;


    public void paintComponent(Graphics g1)
    {
        super.paintComponent(g1);
        g1.setColor(new Color(1.0f,1.0f,1.0f,0.7f));
        g1.fillRect(0, 0, getWidth(), getHeight());
        g1.setColor(new Color(200,200,255));
        g1.drawRect(100,100,200,20);

        LinearGradientPaint p=new LinearGradientPaint(100,100,200,20,pattern,color);
        Graphics2D g2=(Graphics2D)g1;
        g2.setPaint(p);
        g2.fillRect(100, 100,progress*2, 20);
    }
    public void setProgress(int prog)
    {
        progress=prog;
        repaint(100,100,200,20);
        //repaint();
    }

}

But,though the GlassPane gets visible but the ProgressBar is not updating. Need Help friends.

This is a classical mistake: you are blocking the EDT (Event Dispatching Thread) with a loop over a Thread.sleep(). The EDT dispatches all GUI events: paint-events, mouse-events, key-events, action-events etc... Since you are looping and sleeping in the EDT (during an ActionEvent), it prevents the display from refreshing (I bet that your GUI becomes unresponsive after you click the button). So

• Rule #1: do not block the EDT
• Rule #2: DO NOT BLOCK THE EDT, which leads directly to
• Rule #3: do not sleep()in the EDT, and
• Rule #4: do not perform any lengthy-operation in the EDT

To work around this problem, use SwingWorker or javax.swing.Timer. This can also work with traditional Thread's and Executors (thread-pools) but you have to make sure that all your attempts to modify the GUI are performed in the EDT.

You may want to have a look at this example which shows how to combine a JProgressBar and a SwingWorker