用netBeans开发的Java swing程序上不显示进度条

用netBeans做了一个程序，但是进度条就是不显示，总是显示一个圆圈，我已经把indeterminate属性设置成false了，   progressbar.setOrientation(JProgressBar.HORIZONTAL);
   progressbar.setMinimum(0);
   progressbar.setMaximum(100);
   progressbar.setValue(0);大致属性就是这样设置的，怎么才能让他显示出来那，谢谢！！！

解决方案 »

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import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;public class SwingProgressBarExample extends JPanel { JProgressBar pbar; static final int MY_MINIMUM = 0; static final int MY_MAXIMUM = 100; public SwingProgressBarExample() {
 pbar = new JProgressBar();
 pbar.setMinimum(MY_MINIMUM);
 pbar.setMaximum(MY_MAXIMUM);
 add(pbar);
 } public void updateBar(int newValue) {
 pbar.setValue(newValue);
 } public static void main(String args[]) { final SwingProgressBarExample it = new SwingProgressBarExample(); JFrame frame = new JFrame("Progress Bar Example");
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame.setContentPane(it);
 frame.pack();
 frame.setVisible(true); for (int i = MY_MINIMUM; i <= MY_MAXIMUM; i++) {
 final int percent = i;
 try {
 SwingUtilities.invokeLater(new Runnable() {
 public void run() {
 it.updateBar(percent);
 }
 });
 java.lang.Thread.sleep(100);
 } catch (InterruptedException e) {
 ;
 }
 }
 }
}
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.html.*;public class SwingProgressBar{
 final static int interval = 1000;
 int i;
 JLabel label;
 JProgressBar pb;
 Timer timer;
 JButton button; public SwingProgressBar() {
 JFrame frame = new JFrame("Swing Progress Bar");
 button = new JButton("Start");
 button.addActionListener(new ButtonListener()); pb = new JProgressBar(0, 20);
 pb.setValue(0);
 pb.setStringPainted(true); label = new JLabel("Roseindia.net");

 JPanel panel = new JPanel();
 panel.add(button);
 panel.add(pb); JPanel panel1 = new JPanel();
 panel1.setLayout(new BorderLayout());
 panel1.add(panel, BorderLayout.NORTH);
 panel1.add(label, BorderLayout.CENTER);
 panel1.setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
 frame.setContentPane(panel1);
 frame.pack();
 frame.setVisible(true);
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create a timer.
 timer = new Timer(interval, new ActionListener() {
 public void actionPerformed(ActionEvent evt) {
 if (i == 20){
 Toolkit.getDefaultToolkit().beep();
 timer.stop();
 button.setEnabled(true);
 pb.setValue(0);
 String str = "<html>" + "" + "" +
"Downloading completed." + "" + "" + "</html>";
 label.setText(str);
 }
 i = i + 1;
 pb.setValue(i);
 }
 });
 } class ButtonListener implements ActionListener {
 public void actionPerformed(ActionEvent ae) {
 button.setEnabled(false);
 i = 0;
 String str = "<html>" + "" + "" +
"Downloading is in process......." + "" + "" + "</html>";
 label.setText(str);
 timer.start();
 }
 }

 public static void main(String[] args) {
 SwingProgressBar spb = new SwingProgressBar();
 }
}
是在NetBeans里，预览模式和运行模式的结果不一样吧？
你好，在netbeans生成的form代码中，progressBar是被设置为不可见的，你可以在你的***View.java代码中找到：
progressBar.setVisible(false);
如果想让他运行时便可见，把它改成
progressBar.setVisible(true);那个圆圈是进程动画，在resource文件夹中那16张圆圈图片就是用来做动画效果的。
好像还是有问题，我仔细的看了看自动生成的代码，好像是用java.beans.PropertyChangeListener实现的动画和进度条，他下面有几个if判断，但是有一点我还是看不懂public void propertyChange(java.beans.PropertyChangeEvent evt) {
                String propertyName = evt.getPropertyName();
                if ("started".equals(propertyName)) {这里面的字符串started是从哪里得到的呢？
像下面这段代码，if ("background".equals(property)）这句代码，从程序中看不出有那个属性叫 background呀！但是我在控制台把property打印出来，property确实是等于background，这到底是怎么回事高手过来帮忙看一下！！！
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.JButton;
import javax.swing.JFrame;public class BoundSample {
  public static void main(String args[]) {
    JFrame frame = new JFrame("Button Sample");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    final JButton button1 = new JButton("Select Me");
    final JButton button2 = new JButton("No Select Me");    ActionListener actionListener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        JButton button = (JButton) actionEvent.getSource();
        int red = (int) (Math.random() * 255);
        int green = (int) (Math.random() * 255);
        int blue = (int) (Math.random() * 255);
        button.setBackground(new Color(red, green, blue));
      }
    };    PropertyChangeListener propertyChangeListener = new PropertyChangeListener() {
      public void propertyChange(PropertyChangeEvent propertyChangeEvent) {
        String property = propertyChangeEvent.getPropertyName();
        System.out.println(property);
        if ("background".equals(property)) {
          button2.setBackground((Color) propertyChangeEvent.getNewValue());
        }
      }
    };    button1.addActionListener(actionListener);
    button1.addPropertyChangeListener(propertyChangeListener);
    button2.addActionListener(actionListener);    Container contentPane = frame.getContentPane();
    contentPane.add(button1, BorderLayout.NORTH);
    contentPane.add(button2, BorderLayout.SOUTH);
    frame.setSize(300, 100);
    frame.setVisible(true);
  }
}