如何实现一个下拉框为JTree的Combox

public class JTreeComboBox extends JComboBox{
/**
* 显示用的树
*/
private JTree tree;

public JTreeComboBox(){
this(new JTree());
}

public JTreeComboBox(JTree tree){
this.setTree(tree);
}
/**
* 设置树
* @param tree JTree
*/
public void setTree(JTree tree){
this.tree = tree;
if(tree != null){
this.setSelectedItem(tree.getSelectionPath());
this.setRenderer(new JTreeComboBoxRenderer());
}
this.updateUI();
}
/**
* 取得树
* @return JTree
*/
public JTree getTree(){
return tree;
}
/**
* 设置当前选择的树路径
* @param o Object
*/
public void setSelectedItem(Object o){
tree.setSelectionPath((TreePath)o);
getModel().setSelectedItem(o);
}
public void updateUI(){
ComboBoxUI cui = (ComboBoxUI)UIManager.getUI(this);
if(cui instanceof MetalComboBoxUI){
cui = new MetalJTreeComboBoxUI();
} else if(cui instanceof MotifComboBoxUI){
cui = new MotifJTreeComboBoxUI();
} else {
cui = new WindowsJTreeComboBoxUI();
}
setUI(cui);
}
// UI Inner classes -- one for each supported Look and Feel
class MetalJTreeComboBoxUI extends MetalComboBoxUI{
protected ComboPopup createPopup(){
return new TreePopup(comboBox);
}
}
class WindowsJTreeComboBoxUI extends WindowsComboBoxUI{
protected ComboPopup createPopup(){
return new TreePopup(comboBox);
}
}

class MotifJTreeComboBoxUI extends MotifComboBoxUI{
protected ComboPopup createPopup(){
return new TreePopup(comboBox);
}
}
/**
* <p>Title: OpenSwing</p>
* <p>Description: 树形结构而来的DefaultListCellRenderer </p>
* <p>Copyright: Copyright (c) 2004</p>
* <p>Company: </p>
* @author <a href="mailto:sunkingxie@hotmail.com" mce_href="mailto:sunkingxie@hotmail.com">SunKing</a>
* @version 1.0
*/

class JTreeComboBoxRenderer extends DefaultListCellRenderer{
public Component getListCellRendererComponent(JList list, Object value,
int index, boolean isSelected, boolean cellHasFocus){
if(value != null){
TreePath path = (TreePath)value;
TreeNode node = (TreeNode)path.getLastPathComponent();
value = node;
TreeCellRenderer r = tree.getCellRenderer();
JLabel lb = (JLabel)r.getTreeCellRendererComponent(
tree, value, isSelected, false, node.isLeaf(), index,
cellHasFocus);
return lb;
}
return super.getListCellRendererComponent(list, value, index,
isSelected, cellHasFocus);
}
}
/**
* 测试
*/
public static void main(String args[]){
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception e) {
e.printStackTrace();
}
JFrame frame = new JFrame("JTreeComboBox");
final JTreeComboBox box = new JTreeComboBox(new JTree());
box.setPreferredSize(new Dimension(300, 28));
frame.getContentPane().add(box);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
}
/**
* <p>Title: JTreeComboBox</p>
* <p>Description: TreePopup</p>
* <p>Copyright: Copyright (c) 2004</p>
* <p>Company: </p>
* @author  <a href="mailto:rockis@msn.com" mce_href="mailto:rockis@msn.com">zhanglei</a>
*  && <a href="mailto:sunkingxie@hotmail.com" mce_href="mailto:sunkingxie@hotmail.com">SunKing</a>
* @version 1.0
*/
class TreePopup extends JPopupMenu implements ComboPopup{
protected JTreeComboBox comboBox;
protected JScrollPane scrollPane;
protected MouseMotionListener mouseMotionListener;
protected MouseListener mouseListener;
private MouseListener treeSelectListener = new MouseAdapter(){
public void mouseReleased(MouseEvent e){
JTree tree = (JTree)e.getSource();
TreePath tp = tree.getPathForLocation(e.getPoint().x,
e.getPoint().y);
if(tp == null){
return;
}
comboBox.setSelectedItem(tp);
togglePopup();
MenuSelectionManager.defaultManager().clearSelectedPath();
}
};

public TreePopup(JComboBox comboBox){
this.comboBox = (JTreeComboBox)comboBox;
setBorder(BorderFactory.createLineBorder(Color.black));
setLayout(new BorderLayout());
setLightWeightPopupEnabled(comboBox.isLightWeightPopupEnabled());
JTree tree = this.comboBox.getTree();
if(tree != null){
scrollPane = new JScrollPane(tree);
scrollPane.setBorder(null);
add(scrollPane, BorderLayout.CENTER);
tree.addMouseListener(treeSelectListener);
}
}

public void show(){
updatePopup();
show(comboBox, 0, comboBox.getHeight());
comboBox.getTree().requestFocus();
}

public void hide(){
setVisible(false);
comboBox.firePropertyChange("popupVisible", true, false);
}
protected JList list = new JList();
public JList getList(){
return list;
}

public MouseMotionListener getMouseMotionListener(){
if(mouseMotionListener == null){
mouseMotionListener = new MouseMotionAdapter(){};
}
return mouseMotionListener;
}

public KeyListener getKeyListener(){
return null;
}
public void uninstallingUI(){}
/**
* Implementation of ComboPopup.getMouseListener().
*
* @return a <code>MouseListener</code> or null
* @see ComboPopup#getMouseListener
*/
public MouseListener getMouseListener(){
if(mouseListener == null){
mouseListener = new InvocationMouseHandler();
}
return mouseListener;
}

protected void togglePopup(){
if(isVisible()){
hide();
} else{
show();
}
}

protected void updatePopup(){
setPreferredSize(new Dimension(comboBox.getSize().width, 200));
Object selectedObj = comboBox.getSelectedItem();
if(selectedObj != null){
TreePath tp = (TreePath)selectedObj;
((JTreeComboBox)comboBox).getTree().setSelectionPath(tp);
}
}

protected class InvocationMouseHandler extends MouseAdapter{
public void mousePressed(MouseEvent e){
if(!SwingUtilities.isLeftMouseButton(e) || !comboBox.isEnabled()){
return;
}
if(comboBox.isEditable()){
Component comp = comboBox.getEditor().getEditorComponent();
if((!(comp instanceof JComponent)) ||
((JComponent)comp).isRequestFocusEnabled()){
comp.requestFocus();
}
} else if(comboBox.isRequestFocusEnabled()){
comboBox.requestFocus();
}
togglePopup();
}
}
}