Java如何扩展或折叠所有JTree节点？
本示例演示了如何在java.swing.JTreeswing组件中使用全部展开和/或折叠所有功能。
package org.nhooo.example.swing;
import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import javax.swing.tree.TreeNode;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.Enumeration;
public class JTreeNodeAutoExpandCollapse extends JFrame {
public JTreeNodeAutoExpandCollapse() throws HeadlessException {
initializeUI();
}
private void initializeUI() {
setSize(400, 400);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
DefaultMutableTreeNode chapter1 = new DefaultMutableTreeNode("Chapter 1");
DefaultMutableTreeNode sub1 = new DefaultMutableTreeNode("1.1");
DefaultMutableTreeNode sub2 = new DefaultMutableTreeNode("1.2");
DefaultMutableTreeNode sub3 = new DefaultMutableTreeNode("1.3");
DefaultMutableTreeNode sub31 = new DefaultMutableTreeNode("1.3.1");
DefaultMutableTreeNode sub32 = new DefaultMutableTreeNode("1.3.2");
root.add(chapter1);
chapter1.add(sub1);
chapter1.add(sub2);
chapter1.add(sub3);
sub3.add(sub31);
sub3.add(sub32);
final JTree tree = new JTree(root);
expandTree(tree, false);
JScrollPane pane = new JScrollPane(tree);
pane.setPreferredSize(new Dimension(400, 400));
JPanel buttonPanel = new JPanel(new BorderLayout());
JButton expandAll = new JButton("Expand All");
expandAll.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
expandTree(tree, true);
}
});
JButton collapseAll = new JButton("Collapse All");
collapseAll.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
expandTree(tree, false);
}
});
buttonPanel.add(expandAll, BorderLayout.WEST);
buttonPanel.add(collapseAll, BorderLayout.EAST);
getContentPane().setLayout(new BorderLayout());
getContentPane().add(pane, BorderLayout.CENTER);
getContentPane().add(buttonPanel, BorderLayout.SOUTH);
}
private void expandTree(JTree tree, boolean expand) {
TreeNode root = (TreeNode) tree.getModel().getRoot();
expandAll(tree, new TreePath(root), expand);
}
private void expandAll(JTree tree, TreePath path, boolean expand) {
TreeNode node = (TreeNode) path.getLastPathComponent();
if (node.getChildCount() >= 0) {
Enumeration enumeration = node.children();
while (enumeration.hasMoreElements()) {
TreeNode n = (TreeNode) enumeration.nextElement();
TreePath p = path.pathByAddingChild(n);
expandAll(tree, p, expand);
}
}
if (expand) {
tree.expandPath(path);
} else {
tree.collapsePath(path);
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new JTreeNodeAutoExpandCollapse().setVisible(true);
}
});
}
}