我想实现树， 要像myeclipse中的package explorer视图中的树那样的，那上面的树一个项目一个根，那是一个树还是多个树？
如果是多个树，在一个滚动面板上如果加多个树呢，一个滚动面板的viewport只能显示一个组件，viewport里加一个jpanel，jpanel里加两个树，tree展开时，滚动条又不出来。
如果只是一个树，用vector构造jtree，可以显示多个根的树，但显示出来后，再动态添加到vector里的节点就显示不了。
应该怎么弄呢？
如果是多个树，在一个滚动面板上如果加多个树呢，一个滚动面板的viewport只能显示一个组件，viewport里加一个jpanel，jpanel里加两个树，tree展开时，滚动条又不出来。
如果只是一个树，用vector构造jtree，可以显示多个根的树，但显示出来后，再动态添加到vector里的节点就显示不了。
应该怎么弄呢？
package components;/**
* 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.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreeSelectionModel;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.ImageIcon;import java.net.URL;
import java.io.IOException;
import java.awt.Dimension;
import java.awt.GridLayout;public class TreeIconDemo extends JPanel
implements TreeSelectionListener {
private JEditorPane htmlPane;
private JTree tree;
private URL helpURL;
private static boolean DEBUG = false; public TreeIconDemo() {
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);
tree.setRootVisible(false);
//Set the icon for leaf nodes.
ImageIcon leafIcon = createImageIcon("images/middle.gif");
if (leafIcon != null) {
DefaultTreeCellRenderer renderer = new DefaultTreeCellRenderer();
renderer.setLeafIcon(leafIcon);
tree.setCellRenderer(renderer);
} else {
System.err.println("Leaf icon missing; using default.");
} //Listen for when the selection changes.
tree.addTreeSelectionListener(this); //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 = TreeIconDemo.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 = TreeIconDemo.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);
} /** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
java.net.URL imgURL = TreeIconDemo.class.getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
} /**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("TreeIconDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane.
TreeIconDemo newContentPane = new TreeIconDemo();
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();
}
});
}
}