java中使用进度条为何不能更新进度条?
java进度条显示下载进度,我在每写一次数据时都setValue(setValue);但进度条到下载完后一次完成显示,而不是每次显示进度,请高手帮我看一下问题出在哪里?
代码如下:
FileLoad.java:
import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.event.*;
public class FileLoad extends JFrame implements ActionListener
{
JPanel norJp=new JPanel();
JPanel souJp=new JPanel();
JLabel addLabel=new JLabel( "下载地址: ");
JTextField jtf=new JTextField(20);
JButton jb=new JButton( "下载 ");
JProgressBar jpb=new JProgressBar(0,0,500);
public static void main(String[] args)
{
new FileLoad();
}
public FileLoad()
{
this.setTitle( "FileLoad ");
this.setSize(500,200);
Container con=super.getContentPane();
BorderLayout border=new BorderLayout();
con.setLayout(border);
jb.addActionListener(this);
norJp.setLayout(new FlowLayout());
norJp.add(addLabel);
norJp.add(jtf);
norJp.add(jb);
souJp.setLayout(new FlowLayout());
jpb.setValue(50);
souJp.add(jpb);
con.add(norJp,BorderLayout.NORTH);
con.add(souJp,BorderLayout.CENTER);
this.show();
}
public void actionPerformed(ActionEvent e)
{
//System.out.println( "++++++++ ");
int i=0;
int value=10;
if(e.getSource()==jb)
{
//String jtfStr=jtf.getText();
new URLFileLoad(jpb,this,souJp,jtf);
//System.out.println( "jtfStr ");
}
}
}
URLFileLoad.java:
import java.io.*;
import java.net.*;
import java.util.*;
import java.awt.*;
import javax.swing.*;
public class URLFileLoad
{
JProgressBar jpb;
public URLFileLoad(JProgressBar jpb,JFrame frame,JPanel jpl,JTextField jtf)
{
try
{
this.jpb=jpb;
FileOutputStream out=new FileOutputStream( "e:\\UUCall3.exe ");
String urlStr=jtf.getText();
System.out.println( "urlStr= "+urlStr);
//URL url=new URL( "http://127.0.0.1:8585/manager/UUCall3.exe ");
URL url=new URL(urlStr);
URLConnection urlCon=url.openConnection();
Map m=urlCon.getHeaderFields();
Set set=m.entrySet();
Iterator it=set.iterator();
while(it.hasNext())
{
Map.Entry me=(Map.Entry)it.next();
System.out.println(me.getKey()+ ": "+me.getValue());
}
String fileStr=(String)m.get( "Content-Length ").toString();
fileStr=fileStr.replace( '[ ', ' ');
fileStr=fileStr.replace( '] ', ' ');
fileStr=fileStr.trim();
System.out.println(fileStr);
int fileLen=Integer.valueOf(fileStr);
//System.out.println( "k= "+k);
InputStream in=urlCon.getInputStream();
BufferedInputStream buffIn=new BufferedInputStream(in);
byte[] buf=new byte[1024*10];
int size=0;
int fileNum=0;
int setValue=0;
while((size=buffIn.read(buf))!=-1)
{ //System.out.println( "fileNum "+fileNum);
out.write(buf,0,size);
if(fileNum> 1024)
{
System.out.println( "已经下载了 "+fileNum/1024+ "k ");
}
fileNum+=size;
setValue+=5;
jpb.setValue(setValue);
frame.setVisible(true);
Thread.sleep(500);
}
}
catch(Exception e)
{
System.out.println(e);
}
}
}
[解决办法]
mark
[解决办法]
mark
[解决办法]
小菜无力，只能帮顶
[解决办法]
1.文件太小
2.进度条没有刷新
------解决方案--------------------
一般来说，可能的原因是你没有使用多线程。
一下是一个示例程序：JRE 1.6环境下通过编译。
//package components;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.beans.*;
import java.util.Random;
public class ProgressBarDemo extends JPanel
implements ActionListener,
PropertyChangeListener {
private JProgressBar progressBar;
private JButton startButton;
private JTextArea taskOutput;
private Task task;
class Task extends SwingWorker<Void, Void> {
/*
* Main task. Executed in background thread.
*/
@Override
public Void doInBackground() {
Random random = new Random();
int progress = 0;
//Initialize progress property.
setProgress(0);
while (progress < 100) {
//Sleep for up to one second.
try {
Thread.sleep(random.nextInt(1000));
} catch (InterruptedException ignore) {}
//Make random progress.
progress += random.nextInt(10);
setProgress(Math.min(progress, 100));
}
return null;
}
/*
* Executed in event dispatching thread
*/
@Override
public void done() {
Toolkit.getDefaultToolkit().beep();
startButton.setEnabled(true);
setCursor(null); //turn off the wait cursor
taskOutput.append("Done!\n");
}
}
public ProgressBarDemo() {
super(new BorderLayout());
//Create the demo's UI.
startButton = new JButton("Start");
startButton.setActionCommand("start");
startButton.addActionListener(this);
progressBar = new JProgressBar(0, 100);
progressBar.setValue(0);
progressBar.setStringPainted(true);
taskOutput = new JTextArea(5, 20);
taskOutput.setMargin(new Insets(5,5,5,5));
taskOutput.setEditable(false);
JPanel panel = new JPanel();
panel.add(startButton);
panel.add(progressBar);
add(panel, BorderLayout.PAGE_START);
add(new JScrollPane(taskOutput), BorderLayout.CENTER);
setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
}
/**
* Invoked when the user presses the start button.
*/
public void actionPerformed(ActionEvent evt) {
startButton.setEnabled(false);
setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
//Instances of javax.swing.SwingWorker are not reusuable, so
//we create new instances as needed.
task = new Task();
task.addPropertyChangeListener(this);
task.execute();
}
/**
* Invoked when task's progress property changes.
*/
public void propertyChange(PropertyChangeEvent evt) {
if ("progress" == evt.getPropertyName()) {
int progress = (Integer) evt.getNewValue();
progressBar.setValue(progress);
taskOutput.append(String.format(
"Completed %d%% of task.\n", task.getProgress()));
}
}
/**
* Create the GUI and show it. As with all GUI code, this must run
* on the event-dispatching thread.
*/
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("ProgressBarDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create and set up the content pane.
JComponent newContentPane = new ProgressBarDemo();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);
//Display the window.
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
[解决办法]
因为事件处理线程 和UI更新线程都在同一个线程里面,叫Event Dispatch Thread(EDT),
所以,当你在处理事件的时候,是很会影响效率的
还有,你的组件应该一开始就让它显示出来,然后再起个线程 去读取文件,然后边读文件边更新进度条
