java - 无法使用expandPath方法扩展JTree

Question

I've used an example by Ian F. Darwin关于如何在 JTree 上显示文件系统，虽然代码对我来说很清楚，但我不明白为什么我无法在 TreeSelectionListener 的 valueChanged 上伸展树(Splay Tree)。代码如下:

package ericsonwrp.republica.vintage.caixa;

/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.io.File;
import java.util.Collections;
import java.util.Vector;

import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;

/**
 * Display a file system in a JTree view
 * 
 * @version $Id: FileTree.java,v 1.9 2004/02/23 03:39:22 ian Exp $
 * @author Ian Darwin
 */
public class FileTree extends JPanel {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private JTree tree;
    private JScrollPane scrollpane;

    /** Construct a FileTree */
    public FileTree(File dir) {
        setLayout(new BorderLayout());

        tree = new JTree(addNodes(null, dir));
        tree.setRootVisible(false);

        // Add a listener
        tree.addTreeSelectionListener(new TreeSelectionListener() {
            public void valueChanged(TreeSelectionEvent e) {
                DefaultMutableTreeNode node = (DefaultMutableTreeNode) e
                        .getPath().getLastPathComponent();
                TreePath p = new TreePath(node.getPath());
                tree.expandPath(p); // HERE <<<<<<<<<<<<<<
            }
        });

        scrollpane = new JScrollPane();
        scrollpane.getViewport().add(tree);
        add(BorderLayout.CENTER, scrollpane);
    }

    /** Add nodes from under "dir" into curTop. Highly recursive. */
    DefaultMutableTreeNode addNodes(DefaultMutableTreeNode curTop, File dir) {
        String curPath = dir.getPath();
        DefaultMutableTreeNode curDir = new DefaultMutableTreeNode(curPath);
        if (curTop != null) { // should only be null at root
            curTop.add(curDir);
        }
        Vector<String> ol = new Vector<String>();
        String[] tmp = dir.list();
        for (int i = 0; i < tmp.length; i++)
            ol.addElement(tmp[i]);
        Collections.sort(ol, String.CASE_INSENSITIVE_ORDER);
        File f;
        Vector<String> files = new Vector<String>();
        // Make two passes, one for Dirs and one for Files. This is #1.
        for (int i = 0; i < ol.size(); i++) {
            String thisObject = (String) ol.elementAt(i);
            String newPath;
            if (curPath.equals("."))
                newPath = thisObject;
            else
                newPath = curPath + File.separator + thisObject;
            if ((f = new File(newPath)).isDirectory())
                addNodes(curDir, f);
            else
                files.addElement(thisObject);
        }
        // Pass two: for files.
        for (int fnum = 0; fnum < files.size(); fnum++)
            curDir.add(new DefaultMutableTreeNode(files.elementAt(fnum)));
        return curDir;
    }

    public Dimension getMinimumSize() {
        return new Dimension(200, 400);
    }

    public Dimension getPreferredSize() {
        return new Dimension(200, 400);
    }

}

这是我的“FileChooser”与此 JTree 的直观示例:

正如您所看到的，该节点应该在 valueChanged 上展开，但这并没有发生(“Games”是一个文件夹)。

Answer 1

在你的图片中，Games 不是一个文件夹。看图来自your link 。 addNodes() 中出现问题。你无法展开一片叶子;)

尝试使用new File(".")调用FileTree。您应该会看到您的项目文件夹。这对我有用。当我尝试调用 new FileTree(new File("/")) 来获取所有文件夹时...此处 addNodes() 失败。

使用this solution .

也许你必须做出一些改变:

... implements Comparable<File> {

和

public int compareTo(File object)...