在JTree上获取多个根目录来选择叶子 - Swing

Question

我一直使用JTree来获取系统的multiple root directories，使用例子FileTreeModel.java来实现。并且还试图获取选定的叶子（路径），但它会抛出cast error，请给我一些指示，已经发布了到目前为止已经尝试过的代码。谢谢。

import java.io.File;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
import java.io.File;

public class FileTreeDemo {
   public static void main(String[] args) {
   // Figure out where in the filesystem to start displaying
    File root;
if (args.length > 0) {
    root = new File(args[0]);
    //System.out.println(args.length);
    }
else root = new File(System.getProperty("user.home"));
    //System.out.println(args.length);

// Create a TreeModel object to represent our tree of files
FileTreeModel model = new FileTreeModel(root);


// Create a JTree and tell it to display our model
JTree tree = new JTree();
tree.setModel(model);
tree.setRootVisible(true);
tree.setShowsRootHandles(true);
//tree.setShowsRootHandles(true);

// The JTree can get big, so allow it to scroll.
JScrollPane scrollpane = new JScrollPane(tree);

// Display it all in a window and make the window appear
JFrame frame = new JFrame("FileTreeDemo");
frame.getContentPane().add(scrollpane, "Center");
frame.setSize(400,600);
frame.setVisible(true);

// Add a listener
tree.addTreeSelectionListener(new TreeSelectionListener() {
  public void valueChanged(TreeSelectionEvent e) {
    DefaultMutableTreeNode node = (DefaultMutableTreeNode) e
        .getPath().getLastPathComponent();
    System.out.println("You selected " + node);
      }
    });

  }
}

class FileTreeModel implements TreeModel {
  protected File root;
  public FileTreeModel(File root) { this.root = root; }

  public Object getRoot() { return root; }

  public boolean isLeaf(Object node) {  return ((File)node).isFile(); }

  public int getChildCount(Object parent) {
     String[] children = ((File)parent).list();
    if (children == null) return 0;
    return children.length;
  }

  public Object getChild(Object parent, int index) {
    String[] children = ((File)parent).list();
    if ((children == null) || (index >= children.length)) return null;
    return new File((File) parent, children[index]);
  }

  public int getIndexOfChild(Object parent, Object child) {
    String[] children = ((File)parent).list();
    if (children == null) return -1;
    String childname = ((File)child).getName();
    for(int i = 0; i < children.length; i++) {
      if (childname.equals(children[i])) return i;
    }
    return -1;
  }

  public void valueForPathChanged(TreePath path, Object newvalue) {}


  public void addTreeModelListener(TreeModelListener l) {}
  public void removeTreeModelListener(TreeModelListener l) {}
}

Answer 1

在你的模型中你存储File而不是DefaultMutableTreeNode，因为你在这里得到ClassCastException：

DefaultMutableTreeNode node = (DefaultMutableTreeNode)e.getPath().getLastPathComponent();

像下一个一样改变你的听众：

tree.addTreeSelectionListener(new TreeSelectionListener() {
        public void valueChanged(TreeSelectionEvent e) {
            File node = (File) e.getPath().getLastPathComponent();
            System.out.println("You selected " + node);
        }
    });