import Java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
import java.io.*;
import java.net.*;
import java.util.*;
import java.applet.*;
/**
* <p>Title: Applet中使用SWING</p>
* <p>Description: 使用SWING的JApplet实现树功能。</p>
* <p>Copyright: Copyright (c) 2003</p>
* <p>Filename: PageTree.java</p>
* @version 1.0
*/
public class PageTree extends JApplet implements TreeSelectionListener {
DefaultMutableTreeNode[] nodeAt = new DefaultMutableTreeNode[256];
String target = null;
Hashtable links = new Hashtable();
AppletContext context;
public void init() {
//获取Applet的内容
context = getAppletContext();
//定义根节点
DefaultMutableTreeNode root = null;
getContentPane().setLayout(new BorderLayout());
//获取参数。定义的数据配置文件。
String s = getParameter("file");
if (s != null) {
try {
//使用URL方式打开数据文件，实现在网络上使用。
URL url = new URL(getDocumentBase(), s);
BufferedReader br = new BufferedReader(
new InputStreamReader(url.openStream(), "JISAutoDetect"));
//读取第一行数据，假如为空则不执行
String line = br.readLine();
if (line == null) return;
root = new DefaultMutableTreeNode(line);
nodeAt[0] = root;
int level = 0;
while ((line = br.readLine()) != null) {
//使用“”分开数据
StringTokenizer st = new StringTokenizer(line, "");
String token = st.nextToken();
int n = countSpaces(token);
//添加节点名称
DefaultMutableTreeNode node = new DefaultMutableTreeNode(token.trim());
//计算节点级数
for (int i = level + 1; i < n; i++) {
DefaultMutableTreeNode dummy = new DefaultMutableTreeNode("");
nodeAt[i].add(dummy);
nodeAt[i+1] = dummy;
}
level = n;
nodeAt[n].add(node);
nodeAt[n+1] = node;
//对“”符号后的数据进行处理
if (st.hasMoreTokens()) {
token = st.nextToken();
try {
url = new URL(token.trim());
links.put(node, url);
} catch (MalformedURLException ex) {
ex.printStackTrace();
}
}
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
s = getParameter("target");
if (s != null) target = s.trim();
JTree tree = new JTree(root);
//添加树的选择监听
tree.addTreeSelectionListener(this);
JScrollPane jsp = new JScrollPane(tree);
getContentPane().add(jsp, BorderLayout.CENTER);
}
}
/**
*<br>方法说明：计算空格数
*<br>输入参数：
*<br>返回类型：
*/
private int countSpaces(String s) {
int n = 0;
while (s.charAt(n) == ´ ´) {
n++;
}
return n;
}
/**
*<br>方法说明：树选择监听实现方法
*<br>输入参数：TreeSelectionEvent e 选择树节点事件
*<br>返回类型：
*/
public void valueChanged(TreeSelectionEvent e) {
TreePath path = e.getPath();
Object o = path.getLastPathComponent();
URL url = (URL)links.get(o);
if (url != null) {
System.out.println(links.get(o));
//打开连接，通知浏览器加载网页（使用浏览器打开Applet的情况下）
context.showDocument(url);
}
}