翻译:java中怎样使用树结构(How to Use Trees)

最近闲的慌,听说思维迟缓是衰老的标志,.为了尽量保持年轻,我对java 2 jdk的JTree的应用做了一个翻译,首次尝试翻译,有许多不对的地方,还请高手指正.

怎样使用树结构(How to Use Trees)(一)

使用Jtree类,你可以展示有层次关系的数据.一个JTree的实例并不包含你的数据,它只是简单的展示一下你的数据而已.象其他的Swing组件一样,树通过查询它的数据模型得到数据,下面是关于树结构的图片:

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如前所述,JTree垂直的展示它的数据.每一行展示一条树结构的数据,被称作一个”节点”每个树结构都有一个根节点,所有其它节点都由此派生而来.默认的,树结构将显示根节点,但是你也可以做另外的处理.一个节点可以拥有子节点,也可以没有子节点.我们提到的有子节点的节点,叫做分支节点.没有子节点的节点叫做叶节点(leaf nodes).分支节点可以拥有任意多的子节点.用户可以通过点击分支节点来折叠或者展开它----使它的子节点可见或者不可见.默认的,除开根节点的所有分支节点的初始状态都是折叠的.通过监听树结构的扩展事件,程序可以发现分支节点的扩展状态是否改变.

本文余下部分将讨论如下主题:

增加一个树结构

响应节点选择事件

个性花树结构的显示

动态改变树结构

增加一个数字模型

Tree API

使用树的一些例子

增加一个树结构

下面是一个应用的图片,上半部分在一个可滚动面板中展示了一个树结构

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1:用Java Web Start运行TreeDemo.或者自己动手编译如下代码:

文件名称:TreeDemo.java

/**

* A 1.4 application that requires the following additional files:

* TreeDemoHelp.html

* arnold.html

* bloch.html

* chan.html

* jls.html

* swingtutorial.html

* tutorial.html

* tutorialcont.html

* vm.html

*/

import javax.swing.JEditorPane;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.JSplitPane;

import javax.swing.UIManager;

import javax.swing.JTree;

import javax.swing.tree.DefaultMutableTreeNode;

import javax.swing.tree.TreeSelectionModel;

import javax.swing.event.TreeSelectionEvent;

import javax.swing.event.TreeSelectionListener;

import java.net.URL;

import java.io.IOException;

import java.awt.Dimension;

import java.awt.GridLayout;

public class TreeDemo extends JPanel

implements TreeSelectionListener {

private JEditorPane htmlPane;

private JTree tree;

private URL helpURL;

private static boolean DEBUG = false;

//Optionally play with line styles. Possible values are

//"Angled" (the default), "Horizontal", and "None".

private static boolean playWithLineStyle = false;

private static String lineStyle = "Horizontal";

//Optionally set the look and feel.

private static boolean useSystemLookAndFeel = false;

public TreeDemo() {

super(new GridLayout(1,0));

//Create the nodes.

DefaultMutableTreeNode top =

new DefaultMutableTreeNode("The Java Series");

createNodes(top);

//Create a tree that allows one selection at a time.

tree = new JTree(top);

tree.getSelectionModel().setSelectionMode

(TreeSelectionModel.SINGLE_TREE_SELECTION);

//Listen for when the selection changes.

tree.addTreeSelectionListener(this);

if (playWithLineStyle) {

System.out.println("line style = " + lineStyle);

tree.putClientProperty("JTree.lineStyle", lineStyle);

}

//Create the scroll pane and add the tree to it.

JScrollPane treeView = new JScrollPane(tree);

//Create the HTML viewing pane.

htmlPane = new JEditorPane();

htmlPane.setEditable(false);

initHelp();

JScrollPane htmlView = new JScrollPane(htmlPane);

//Add the scroll panes to a split pane.

JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT);

splitPane.setTopComponent(treeView);

splitPane.setBottomComponent(htmlView);

Dimension minimumSize = new Dimension(100, 50);

htmlView.setMinimumSize(minimumSize);

treeView.setMinimumSize(minimumSize);

splitPane.setDividerLocation(100); //XXX: ignored in some releases

//of Swing. bug 4101306

//workaround for bug 4101306:

//treeView.setPreferredSize(new Dimension(100, 100));

splitPane.setPreferredSize(new Dimension(500, 300));

//Add the split pane to this panel.

add(splitPane);

}

/** Required by TreeSelectionListener interface. */

public void valueChanged(TreeSelectionEvent e) {

DefaultMutableTreeNode node = (DefaultMutableTreeNode)

tree.getLastSelectedPathComponent();

if (node == null) return;

Object nodeInfo = node.getUserObject();

if (node.isLeaf()) {

BookInfo book = (BookInfo)nodeInfo;

displayURL(book.bookURL);

if (DEBUG) {

System.out.print(book.bookURL + ": \n ");

}

} else {

displayURL(helpURL);

}

if (DEBUG) {

System.out.println(nodeInfo.toString());

}

}

private class BookInfo {

public String bookName;

public URL bookURL;

public BookInfo(String book, String filename) {

bookName = book;

bookURL = TreeDemo.class.getResource(filename);

if (bookURL == null) {

System.err.println("Couldn't find file: "

+ filename);

}

}

public String toString() {

return bookName;

}

}

private void initHelp() {

String s = "TreeDemoHelp.html";

helpURL = TreeDemo.class.getResource(s);

if (helpURL == null) {

System.err.println("Couldn't open help file: " + s);

} else if (DEBUG) {

System.out.println("Help URL is " + helpURL);

}

displayURL(helpURL);

}

private void displayURL(URL url) {

try {

if (url != null) {

htmlPane.setPage(url);

} else { //null url

htmlPane.setText("File Not Found");

if (DEBUG) {

System.out.println("Attempted to display a null URL.");

}

}

} catch (IOException e) {

System.err.println("Attempted to read a bad URL: " + url);

}

}

private void createNodes(DefaultMutableTreeNode top) {

DefaultMutableTreeNode category = null;

DefaultMutableTreeNode book = null;

category = new DefaultMutableTreeNode("Books for Java Programmers");

top.add(category);

//original Tutorial

book = new DefaultMutableTreeNode(new BookInfo

("The Java Tutorial: A Short Course on the Basics",

"tutorial.html"));

category.add(book);

//Tutorial Continued

book = new DefaultMutableTreeNode(new BookInfo

("The Java Tutorial Continued: The Rest of the JDK",

"tutorialcont.html"));

category.add(book);

//JFC Swing Tutorial

book = new DefaultMutableTreeNode(new BookInfo

("The JFC Swing Tutorial: A Guide to Constructing GUIs",

"swingtutorial.html"));

category.add(book);

//Bloch

book = new DefaultMutableTreeNode(new BookInfo

("Effective Java Programming Language Guide",

"bloch.html"));

category.add(book);

//Arnold/Gosling

book = new DefaultMutableTreeNode(new BookInfo

("The Java Programming Language", "arnold.html"));

category.add(book);

//Chan

book = new DefaultMutableTreeNode(new BookInfo

("The Java Developers Almanac",

"chan.html"));

category.add(book);

category = new DefaultMutableTreeNode("Books for Java Implementers");

top.add(category);

//VM

book = new DefaultMutableTreeNode(new BookInfo

("The Java Virtual Machine Specification",

"vm.html"));

category.add(book);

//Language Spec

book = new DefaultMutableTreeNode(new BookInfo

("The Java Language Specification",

"jls.html"));

category.add(book);

}

/**

* Create the GUI and show it. For thread safety,

* this method should be invoked from the

* event-dispatching thread.

*/

private static void createAndShowGUI() {

if (useSystemLookAndFeel) {

try {

UIManager.setLookAndFeel(

UIManager.getSystemLookAndFeelClassName());

} catch (Exception e) {

System.err.println("Couldn't use system look and feel.");

}

}

//Make sure we have nice window decorations.

JFrame.setDefaultLookAndFeelDecorated(true);

//Create and set up the window.

JFrame frame = new JFrame("TreeDemo");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//Create and set up the content pane.

TreeDemo newContentPane = new TreeDemo();

newContentPane.setOpaque(true); //content panes must be opaque

frame.setContentPane(newContentPane);

//Display the window.

frame.pack();

frame.setVisible(true);

}

public static void main(String[] args) {

//Schedule a job for the event-dispatching thread:

//creating and showing this application's GUI.

javax.swing.SwingUtilities.invokeLater(new Runnable() {

public void run() {

createAndShowGUI();

}

});

}

}

2:展开节点

点击节点左侧的圆圈图标可展开节点

3:收缩节点

点击节点左侧的圆圈图标可收缩节点

下面分析一下TreeDemo.java代码:

增加JTree实例并且把它放到面板上: