一般情況下，構建一個 SWING 樹，都是先要構建好存放數據的模型 (TreeModel), 在一般情況下，實現起來都沒有問題，但當數據量非常大的時候，一次性構建好 TreeModel ，將會花費很多時間，界面處于灰掉的狀態（當然可以另開其他線程，可以操作其他界面），這個給用戶的感覺非常差。解決這個問題的關鍵在于，樹模型的數據。我們都知道，系統文件是一層一層很有層次性，這樣我們就可以以一個文件（不管是文件還是文件夾）為樹節點，當初次加載樹的時候，點擊樹節點，先判斷其有沒有子節點，若無，就去讀去該節點的保存的文件信息，若為文件夾，就去取其文件夾下的所有文件，構造出樹節點，加到樹中。第二次點擊的時候，就不會去讀磁盤文件系統了。

代碼清單：

import javax.swing.tree.DefaultMutableTreeNode;

import javax.swing.tree.DefaultTreeModel;

import java.io.*;

import java.awt.*;

import javax.swing.*;

import javax.swing.tree.TreeCellRenderer;

import java.awt.event.MouseAdapter;

import java.awt.event.MouseEvent;

import javax.swing.tree.TreePath;

/**

?* <p>Title: JDHSystemFileTree</p>

?* <p>Description: 系統目錄樹，動態生成，解決載入慢的問題 </p>

?* <p>Copyright: Copyright (c) 2007</p>

* @author 蔣家狂潮

?* @version 1.0

?*/

public class SystemFileTree {

??? private DefaultTreeModel model;

??? private JTree tree;

??? public SystemFileTree () {

??????? JFrame f=new JFrame();

??????? f.getContentPane().setLayout(new BorderLayout());

??????? tree=new JTree();

?????? ?tree.addMouseListener(new MouseAdapter(){

??????????? public void mousePressed(MouseEvent e){

??????????????? node_mouseAction(e);

??????????? }

??????? });

??????? JScrollPane scroll=new JScrollPane(tree);

??????? f.getContentPane().add(scroll,BorderLayout.CENTER);

?

??????? f.setLocation(250,250);

??????? f.setSize(new Dimension(300,500));

??????? f.setVisible(true);

??? }

??? private void node_mouseAction(MouseEvent e){

??????? int row = tree.getRowForLocation(e.getX(), e.getY());

??????? PathNode pathNode =null;

??????? if(row != -1){

??????? TreePath path = tree.getPathForRow(row);

??????? pathNode = (PathNode)path.getLastPathComponent();

?

??????? if(pathNode.isFolder()&&pathNode.getChildCount()==0){

??????????? builderNode(pathNode);

??????????? tree.expandPath(path);

??????? }

??????? }

?

??? }

??? private PathNode builderNode(PathNode pathNode){

??????? String filePath= pathNode.getValue().toString();

??????? File file=new File(filePath);

??????? File[] files=file.listFiles();

?????? for(int i=0;i<files.length;i++){

?????????? PathNode node=new PathNode(files[i].getName(), files[i].getAbsolutePath(),files[i].isDirectory());

?????????? pathNode.add(node);

?????? }

??????? return pathNode;

??? }

??? private void initData(String? rootPath){

?

??????? File f=new File(rootPath);

?

??????? PathNode root=new PathNode(f.getName(), rootPath,f.isDirectory());

?

??????? File[] files=f.listFiles();

??????? for(int i=0;i<files.length;i++){

??????????? PathNode node=new PathNode(files[i].getName(), files[i].getAbsolutePath(),files[i].isDirectory());

??????????? root.add(node);

??????? }

?

?

??????? model=new DefaultTreeModel(root);

??????? tree.setModel(model);

??????? FileTreeRenderer renderer=new FileTreeRenderer();

??????? tree.setCellRenderer(renderer);

??????? tree.repaint();

}

?

??? class FileTreeRenderer implements TreeCellRenderer{

??????? private Icon folder_open=new ImageIcon("icons/folder_open.jpg");

??????? private Icon folder_close=new ImageIcon("icons/folder_close.jpg");

??????? private Icon file=new ImageIcon("icons/file.gif");

??????? public Component getTreeCellRendererComponent(JTree tree, Object value,

??????????????? boolean selected, boolean expanded, boolean leaf, int row,

??????????????? boolean hasFocus) {

??????????? JLabel label = null;

?????????? ?if (value != null) {

??????????????? System.out.println(value.getClass().toString());

??????????????? if(value instanceof PathNode){

?

??????????????????? PathNode pathNode = (PathNode) value;

??????????????????? if (pathNode.isFolder()) {

??????????????? ????????if (expanded) {

??????????????????????????? label = new JLabel(pathNode.getUserObject().

?????????????????????????????????????????????? toString(),

?????????????????????????????????????????????? folder_open, JLabel.RIGHT);

??????????????????????? } else if(!expanded||leaf) {

??????????????????????????? label = new JLabel(pathNode.getUserObject().

?????????????????????????????????????????????? toString(),

?????????????????????????????????????????????? folder_close, JLabel.RIGHT);

??????????????????? ????}

??????????????????? } else {

??????????????????????? label = new JLabel(pathNode.getUserObject().toString(),

?????????????????????????????????????????? file, JLabel.RIGHT);

??????????????????? }

??????????????????? return label;

??????????????? }

?? ?????????}

??????????? return label;

??????? }

}

?

??? class PathNode extends DefaultMutableTreeNode{

??????? Object value;

??????? boolean isFolder;

?????? public PathNode(String name,Object value,boolean isFolder){

?????????? super(name);

?????????? this.value=value;

?????????? this.isFolder=isFolder;

??????? }

??????? public Object getValue(){

????????? return value;

??????? }

??????? public boolean isFolder(){

??????????? return isFolder;

??????? }

??? }

??? public static void main(String args[]){

?? ?????JDHSystemFileTree tree=new JDHSystemFileTree();

???????? // 給個路徑作演示

??????? tree.initData("D:/");

??? }

}

?

當然可以進一步實現界面的易用性，就是在初始點擊之后，加載完之前，讓鼠標變成等待的形狀。
???????????????????????