Directory Chooser API

Java swing provides File chooser but, it doesn't provide any direct support for directory chooser. Following code helps to create a system directory chooser

 

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.InputEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.io.File;
import java.util.Arrays;
import java.util.Enumeration;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.UIManager;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.filechooser.FileSystemView;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import javax.swing.tree.TreeSelectionModel;

public class DirectoryChooser extends JTree implements TreeSelectionListener,
  MouseListener {

 private static FileSystemView fsv = FileSystemView.getFileSystemView();

 /* --- Begin Public API ----- */

 public DirectoryChooser() {
  this(null);
 }

 public DirectoryChooser(File dir) {
  super(new DirNode(fsv.getRoots()[0]));
  getSelectionModel().setSelectionMode(
    TreeSelectionModel.SINGLE_TREE_SELECTION);
  setSelectedDirectory(dir);
  addTreeSelectionListener(this);
  addMouseListener(this);
 }

 public void setSelectedDirectory(File dir) {
  if (dir == null) {
   dir = fsv.getDefaultDirectory();
  }
  setSelectionPath(mkPath(dir));
 }

 public File getSelectedDirectory() {
  DirNode node = (DirNode) getLastSelectedPathComponent();
  if (node != null) {
   File dir = node.getDir();
   if (fsv.isFileSystem(dir)) {
    return dir;
   }
  }
  return null;
 }

 public void addActionListener(ActionListener l) {
  listenerList.add(ActionListener.class, l);
 }

 public void removeActionListener(ActionListener l) {
  listenerList.remove(ActionListener.class, l);
 }

 public ActionListener[] getActionListeners() {
  return (ActionListener[]) listenerList
    .getListeners(ActionListener.class);
 }

 /* --- End Public API ----- */

 /* --- TreeSelectionListener Interface ----- */

 public void valueChanged(TreeSelectionEvent ev) {
  File oldDir = null;
  TreePath oldPath = ev.getOldLeadSelectionPath();
  if (oldPath != null) {
   oldDir = ((DirNode) oldPath.getLastPathComponent()).getDir();
   if (!fsv.isFileSystem(oldDir)) {
    oldDir = null;
   }
  }
  File newDir = getSelectedDirectory();
  firePropertyChange("selectedDirectory", oldDir, newDir);
 }

 /* --- MouseListener Interface ----- */

 public void mousePressed(MouseEvent e) {
  if (e.getClickCount() == 2) {
   TreePath path = getPathForLocation(e.getX(), e.getY());
   if (path != null && path.equals(getSelectionPath())
     && getSelectedDirectory() != null) {

    fireActionPerformed("dirSelected", e);
   }
  }
 }

 public void mouseReleased(MouseEvent e) {
 }

 public void mouseClicked(MouseEvent e) {
 }

 public void mouseEntered(MouseEvent e) {
 }

 public void mouseExited(MouseEvent e) {
 }

 /* --- Private Section ------ */

 private TreePath mkPath(File dir) {
  DirNode root = (DirNode) getModel().getRoot();
  if (root.getDir().equals(dir)) {
   return new TreePath(root);
  }

  TreePath parentPath = mkPath(fsv.getParentDirectory(dir));
  DirNode parentNode = (DirNode) parentPath.getLastPathComponent();
  Enumeration enumeration = parentNode.children();
  while (enumeration.hasMoreElements()) {
   DirNode child = (DirNode) enumeration.nextElement();
   if (child.getDir().equals(dir)) {
    return parentPath.pathByAddingChild(child);
   }
  }
  return null;
 }

 private void fireActionPerformed(String command, InputEvent evt) {
  ActionEvent e = new ActionEvent(this, ActionEvent.ACTION_PERFORMED,
    command, evt.getWhen(), evt.getModifiers());
  ActionListener[] listeners = getActionListeners();
  for (int i = listeners.length - 1; i >= 0; i--) {
   listeners[i].actionPerformed(e);
  }
 }

 private static class DirNode extends DefaultMutableTreeNode {
  DirNode(File dir) {
   super(dir);
  }

  public File getDir() {
   return (File) userObject;
  }

  public int getChildCount() {
   populateChildren();
   return super.getChildCount();
  }

  public Enumeration children() {
   populateChildren();
   return super.children();
  }

  public boolean isLeaf() {
   return false;
  }

  private void populateChildren() {
   if (children == null) {
    File[] files = fsv.getFiles(getDir(), true);
    Arrays.sort(files);
    for (int i = 0; i < files.length; i++) {
     File f = files[i];
     if (fsv.isTraversable(f).booleanValue()) {
      insert(new DirNode(f), (children == null) ? 0
        : children.size());
     }
    }
   }
  }

  public String toString() {
   return fsv.getSystemDisplayName(getDir());
  }

  public boolean equals(Object o) {
   return (o instanceof DirNode && userObject
     .equals(((DirNode) o).userObject));
  }
 }

 /* --- Main for testing --- */

 public static void main(String[] args) {
  try {
   UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
  } catch (Exception ex) {
  }

  final JDialog dialog = new JDialog((JFrame) null, true);
  final DirectoryChooser dc = new DirectoryChooser();
  final JButton okButton = new JButton("OK");
  final JButton cancelButton = new JButton("Cancel");

  dialog.getContentPane().add(new JScrollPane(dc), BorderLayout.CENTER);

  JPanel buttonPanel = new JPanel();
  buttonPanel.add(okButton);
  buttonPanel.add(cancelButton);
  dialog.getContentPane().add(buttonPanel, BorderLayout.SOUTH);

  ActionListener actionListener = new ActionListener() {
   public void actionPerformed(ActionEvent e) {
    Object c = e.getSource();
    if (c == okButton || c == dc) {
     System.out.println("You selected: "
       + dc.getSelectedDirectory());
    }
    dialog.hide();
   }
  };

  dc.addActionListener(actionListener);
  okButton.addActionListener(actionListener);
  cancelButton.addActionListener(actionListener);

  dc.addPropertyChangeListener(new PropertyChangeListener() {
   public void propertyChange(PropertyChangeEvent ev) {
    if (ev.getPropertyName().equals("selectedDirectory")) {
     okButton.setEnabled(dc.getSelectedDirectory() != null);
    }
   }
  });

  dialog.setBounds(200, 200, 300, 350);
  dc.scrollRowToVisible(Math.max(0, dc.getMinSelectionRow() - 4));
  dialog.show();
  System.exit(0);
 }
}