JTree实现的系统文件目录树

看到很多人问关于用JTree实现资源管理器的方法，在这里我提供一个例子共大家参考，这个例子虽然也是转自其他书，但是JTree的用法，我掌握的差不多了，如果哪位朋友，对此例子有问题，我愿意与他交流。我的email是：[email protected]这个例子涵盖了JTree的大部分属性，希望对大家能够有所帮助。需要一些图标文件，请大家自己复制好相同名字的gif图片放到目录下。

下面是源代码:

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;

import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.event.*;

public class FileTree1
 extends JFrame
{
 public static final ImageIcon ICON_COMPUTER =
  new ImageIcon("computer.gif");
 public static final ImageIcon ICON_DISK =
  new ImageIcon("disk.gif");
 public static final ImageIcon ICON_FOLDER =
  new ImageIcon("folder.gif");
 public static final ImageIcon ICON_EXPANDEDFOLDER =
  new ImageIcon("expandedfolder.gif");

 protected JTree  m_tree;
 protected DefaultTreeModel m_model;
 protected JTextField m_display;

 public FileTree1()
 {
  super("Directories Tree");
  setSize(400, 300);

  DefaultMutableTreeNode top = new DefaultMutableTreeNode(
   new IconData(ICON_COMPUTER, null, "Computer"));

  DefaultMutableTreeNode node;
  File[] roots = File.listRoots();
  for (int k=0; k<roots.length; k++)
  {
   node = new DefaultMutableTreeNode(new IconData(ICON_DISK,
    null, new FileNode(roots[k])));
   top.add(node);
                        node.add( new DefaultMutableTreeNode(new Boolean(true)));
  }

  m_model = new DefaultTreeModel(top);
  m_tree = new JTree(m_model);

                m_tree.putClientProperty("JTree.lineStyle", "Angled");

  TreeCellRenderer renderer = new
   IconCellRenderer();
  m_tree.setCellRenderer(renderer);

  m_tree.addTreeExpansionListener(new
   DirExpansionListener());

  m_tree.addTreeSelectionListener(new
   DirSelectionListener());

  m_tree.getSelectionModel().setSelectionMode(
   TreeSelectionModel.SINGLE_TREE_SELECTION);
  m_tree.setShowsRootHandles(true);
  m_tree.setEditable(false);

  JScrollPane s = new JScrollPane();
  s.getViewport().add(m_tree);
  getContentPane().add(s, BorderLayout.CENTER);

  m_display = new JTextField();
  m_display.setEditable(false);
  getContentPane().add(m_display, BorderLayout.NORTH);

  WindowListener wndCloser = new WindowAdapter()
  {
   public void windowClosing(WindowEvent e)
   {
    System.exit(0);
   }
  };
  addWindowListener(wndCloser);
  
  setVisible(true);
 }

 DefaultMutableTreeNode getTreeNode(TreePath path)
 {
  return (DefaultMutableTreeNode)(path.getLastPathComponent());
 }

 FileNode getFileNode(DefaultMutableTreeNode node)
 {
  if (node == null)
   return null;
  Object obj = node.getUserObject();
  if (obj instanceof IconData)
   obj = ((IconData)obj).getObject();
  if (obj instanceof FileNode)
   return (FileNode)obj;
  else
   return null;
 }

    // Make sure expansion is threaded and updating the tree model
    // only occurs within the event dispatching thread.
    class DirExpansionListener implements TreeExpansionListener
    {
        public void treeExpanded(TreeExpansionEvent event)
        {
             final DefaultMutableTreeNode node = getTreeNode(
                event.getPath());
             final FileNode fnode = getFileNode(node);

            Thread runner = new Thread()
            {
              public void run()
              {
                if (fnode != null && fnode.expand(node))
                {
                  Runnable runnable = new Runnable()
                  {
                    public void run()
                    {
                       m_model.reload(node);
                    }
                  };
                  SwingUtilities.invokeLater(runnable);
                }
              }
            };
            runner.start();
        }

        public void treeCollapsed(TreeExpansionEvent event) {}
    }

 class DirSelectionListener
  implements TreeSelectionListener
 {
  public void valueChanged(TreeSelectionEvent event)
  {
   DefaultMutableTreeNode node = getTreeNode(
    event.getPath());
   FileNode fnode = getFileNode(node);
   if (fnode != null)
    m_display.setText(fnode.getFile().
     getAbsolutePath());
   else
    m_display.setText("");
  }
 }

 public static void main(String argv[])
 {
  new FileTree1();
 }
}

class IconCellRenderer
 extends    JLabel
 implements TreeCellRenderer
{
 protected Color m_textSelectionColor;
 protected Color m_textNonSelectionColor;
 protected Color m_bkSelectionColor;
 protected Color m_bkNonSelectionColor;
 protected Color m_borderSelectionColor;

 protected boolean m_selected;

 public IconCellRenderer()
 {
  super();
  m_textSelectionColor = UIManager.getColor(
   "Tree.selectionForeground");
  m_textNonSelectionColor = UIManager.getColor(
   "Tree.textForeground");
  m_bkSelectionColor = UIManager.getColor(
   "Tree.selectionBackground");
  m_bkNonSelectionColor = UIManager.getColor(
   "Tree.textBackground");
  m_borderSelectionColor = UIManager.getColor(
   "Tree.selectionBorderColor");
  setOpaque(false);
 }

 public Component getTreeCellRendererComponent(JTree tree,
  Object value, boolean sel, boolean expanded, boolean leaf,
  int row, boolean hasFocus)
  
 {
  DefaultMutableTreeNode node =
   (DefaultMutableTreeNode)value;
  Object obj = node.getUserObject();
  setText(obj.toString());

                if (obj instanceof Boolean)
                  setText("Retrieving data...");

  if (obj instanceof IconData)
  {
   IconData idata = (IconData)obj;
   if (expanded)
    setIcon(idata.getExpandedIcon());
   else
    setIcon(idata.getIcon());
  }
  else
   setIcon(null);

  setFont(tree.getFont());
  setForeground(sel ? m_textSelectionColor :
   m_textNonSelectionColor);
  setBackground(sel ? m_bkSelectionColor :
   m_bkNonSelectionColor);
  m_selected = sel;
  return this;
 }
   
 
 public void paintComponent(Graphics g)
 {
  Color bColor = getBackground();
  Icon icon = getIcon();

  g.setColor(bColor);
  int offset = 0;
  if(icon != null && getText() != null)
   offset = (icon.getIconWidth() + getIconTextGap());
  g.fillRect(offset, 0, getWidth() - 1 - offset,
   getHeight() - 1);
  
  if (m_selected)
  {
   g.setColor(m_borderSelectionColor);
   g.drawRect(offset, 0, getWidth()-1-offset, getHeight()-1);
  }
  super.paintComponent(g);
    }
}

class IconData
{
 protected Icon   m_icon;
 protected Icon   m_expandedIcon;
 protected Object m_data;

 public IconData(Icon icon, Object data)
 {
  m_icon = icon;
  m_expandedIcon = null;
  m_data = data;
 }

 public IconData(Icon icon, Icon expandedIcon, Object data)
 {
  m_icon = icon;
  m_expandedIcon = expandedIcon;
  m_data = data;
 }

 public Icon getIcon()
 {
  return m_icon;
 }

 public Icon getExpandedIcon()
 {
  return m_expandedIcon!=null ? m_expandedIcon : m_icon;
 }

 public Object getObject()
 {
  return m_data;
 }

 public String toString()
 {
  return m_data.toString();
 }
}

class FileNode
{
 protected File m_file;

 public FileNode(File file)
 {
  m_file = file;
 }

 public File getFile()
 {
  return m_file;
 }

 public String toString()
 {
  return m_file.getName().length() > 0 ? m_file.getName() :
   m_file.getPath();
 }

 public boolean expand(DefaultMutableTreeNode parent)
 {
  DefaultMutableTreeNode flag =
   (DefaultMutableTreeNode)parent.getFirstChild();
  if (flag==null)   // No flag
   return false;
  Object obj = flag.getUserObject();
  if (!(obj instanceof Boolean))
   return false;      // Already expanded

  parent.removeAllChildren();  // Remove Flag

  File[] files = listFiles();
  if (files == null)
   return true;

  Vector v = new Vector();

  for (int k=0; k<files.length; k++)
  {
   File f = files[k];
   if (!(f.isDirectory()))
    continue;

   FileNode newNode = new FileNode(f);
   
   boolean isAdded = false;
   for (int i=0; i<v.size(); i++)
   {
    FileNode nd = (FileNode)v.elementAt(i);
    if (newNode.compareTo(nd) < 0)
    {
     v.insertElementAt(newNode, i);
     isAdded = true;
     break;
    }
   }
   if (!isAdded)
    v.addElement(newNode);
  }

  for (int i=0; i<v.size(); i++)
  {
   FileNode nd = (FileNode)v.elementAt(i);
   IconData idata = new IconData(FileTree1.ICON_FOLDER,
    FileTree1.ICON_EXPANDEDFOLDER, nd);
   DefaultMutableTreeNode node = new
    DefaultMutableTreeNode(idata);
   parent.add(node);
    
   if (nd.hasSubDirs())
    node.add(new DefaultMutableTreeNode(
     new Boolean(true) ));
  }

  return true;
 }

 public boolean hasSubDirs()
 {
  File[] files = listFiles();
  if (files == null)
   return false;
  for (int k=0; k<files.length; k++)
  {
   if (files[k].isDirectory())
    return true;
  }
  return false;
 }
 
 public int compareTo(FileNode toCompare)
 {
  return  m_file.getName().compareToIgnoreCase(
   toCompare.m_file.getName() );
 }

 protected File[] listFiles()
 {
  if (!m_file.isDirectory())
   return null;
  try
  {
   return m_file.listFiles();
  }
  catch (Exception ex)
  {
   JOptionPane.showMessageDialog(null,
    "Error reading directory "+m_file.getAbsolutePath(),
    "Warning", JOptionPane.WARNING_MESSAGE);
   return null;
  }
 }
}

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