JEditorPane

Question

为什么JEditorPane的read(InputStream,object)总是抛出NullPointException.怎么样才能从InputStream中加载HTML页面呢？

Answer 1

把代码贴出来。这样怎么知道必须从IS里加载吗？用setPage不可以吗

Answer 2

动态库实现的InputStreamprivate class View extends JEditorPane
{
public View()
{
setEditable(false);
setEditorKit(getEditorKitForContentType("text/html"));
}
 public Set(String strURL)
{
 InputStream is = CreateInputStream(strURL); // 动态库实现的stream,测试没问题
 read(is,getEditorKit().createDefaultDocument()); // 异常
}
}

Answer 3

JEditorPane p=new JEditorPane();
    JFrame f=new JFrame();
    f.getContentPane().add(p,BorderLayout.CENTER);
    URL url=new URL("http://www.sina.com.cn");
    p.setEditorKit(p.getEditorKitForContentType("text/html"));
    p.read(url.openStream(),p.getEditorKit().createDefaultDocument());
    f.show();
没问题我想你的问题在CreateInputStream方法,看看传入的string是不是个url格式.为什么不用URL的openStream呢?

Answer 4

使用URL是可以的，但数据在数据库中，不存在真实的地址，由动态库进行重组，解压，解密后生成的数据流。

Answer 5

/**
   @version 1.02 2004-08-22
   @author Cay Horstmann
*/import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import java.util.*;
import javax.swing.*;
import javax.swing.event.*;/**
   This program demonstrates how to display HTML documents
   in an editor pane.
*/
public class EditorPaneTest
{
   public static void main(String[] args)
   {
      JFrame frame = new EditorPaneFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}/**
   This frame contains an editor pane, a text field and button
   to enter a URL and load a document, and a Back button to
   return to a previously loaded document.
*/
class EditorPaneFrame extends JFrame
{
   public EditorPaneFrame()
   {
      setTitle("EditorPaneTest");
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);      final Stack<String> urlStack = new Stack<String>();
      final JEditorPane editorPane = new JEditorPane();
      final JTextField url = new JTextField(30);      // set up hyperlink listener      editorPane.setEditable(false);
      editorPane.addHyperlinkListener(new
         HyperlinkListener()
         {
            public void hyperlinkUpdate(HyperlinkEvent event)
            {
               if (event.getEventType() == HyperlinkEvent.EventType.ACTIVATED)
               {
                  try
                  {
                     // remember URL for back button
                     urlStack.push(event.getURL().toString());
                     // show URL in text field
                     url.setText(event.getURL().toString());
                     editorPane.setPage(event.getURL());
                  }
                  catch (IOException e)
                  {
                     editorPane.setText("Exception: " + e);
                  }
               }
            }
         });      // set up checkbox for toggling edit mode      final JCheckBox editable = new JCheckBox();
      editable.addActionListener(new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               editorPane.setEditable(editable.isSelected());
            }
         });      // set up load button for loading URL      ActionListener listener = new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               try
               {
                  // remember URL for back button
                  urlStack.push(url.getText());
                  editorPane.setPage(url.getText());
               }
               catch (IOException e)
               {
                  editorPane.setText("Exception: " + e);
               }
            }
         };      JButton loadButton = new JButton("Load");
      loadButton.addActionListener(listener);
      url.addActionListener(listener);      // set up back button and button action      JButton backButton = new JButton("Back");
      backButton.addActionListener(new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               if (urlStack.size() <= 1) return;
               try
               {
                  // get URL from back button
                  urlStack.pop();
                  // show URL in text field
                  String urlString = urlStack.peek();
                  url.setText(urlString);
                  editorPane.setPage(urlString);
               }
               catch (IOException e)
               {
                  editorPane.setText("Exception: " + e);
               }
            }
         });      add(new JScrollPane(editorPane), BorderLayout.CENTER);      // put all control components in a panel      JPanel panel = new JPanel();
      panel.add(new JLabel("URL"));
      panel.add(url);
      panel.add(loadButton);
      panel.add(backButton);
      panel.add(new JLabel("Editable"));
      panel.add(editable);      add(panel, BorderLayout.SOUTH);
   }   private static final int DEFAULT_WIDTH = 600;
   private static final int DEFAULT_HEIGHT = 400;
}

Answer 6

找问题是比较烦我还是觉得InputStream is = CreateInputStream(strURL); 有问题。你可以把后面的代码改一下，通过这个is来读取String，然后把String打印出来，看看有没有问题。其实CreateInputStream(strURL); 和URL.openStream()一样的，你也可以通过openStream对流作任何操作，甚至包括加密解密