List files and directories with Jtree and File in Java

Question

I want to create a very very simple file manager with JTree, but I only saw a very hard code and I want to create this script very clean and simple.

Can you help me? How do I List the directories of my computer in JTree?

Answer 1

I wrote the simplest example of a file browser I could think of. It lists all of the directories and files on the C: drive on a Windows computer.

Here's the result.

And here's the code. I put everything together in one class to make it easier to paste here. You should separate the classes.

package com.ggl.testing;

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;

public class FileBrowser implements Runnable {

    private DefaultMutableTreeNode root;

    private DefaultTreeModel treeModel;

    private JTree tree;

    @Override
    public void run() {
        JFrame frame = new JFrame("File Browser");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        File fileRoot = new File("C:/");
        root = new DefaultMutableTreeNode(new FileNode(fileRoot));
        treeModel = new DefaultTreeModel(root);

        tree = new JTree(treeModel);
        tree.setShowsRootHandles(true);
        JScrollPane scrollPane = new JScrollPane(tree);

        frame.add(scrollPane);
        frame.setLocationByPlatform(true);
        frame.setSize(640, 480);
        frame.setVisible(true);

        CreateChildNodes ccn = 
                new CreateChildNodes(fileRoot, root);
        new Thread(ccn).start();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new FileBrowser());
    }

    public class CreateChildNodes implements Runnable {

        private DefaultMutableTreeNode root;

        private File fileRoot;

        public CreateChildNodes(File fileRoot, 
                DefaultMutableTreeNode root) {
            this.fileRoot = fileRoot;
            this.root = root;
        }

        @Override
        public void run() {
            createChildren(fileRoot, root);
        }

        private void createChildren(File fileRoot, 
                DefaultMutableTreeNode node) {
            File[] files = fileRoot.listFiles();
            if (files == null) return;

            for (File file : files) {
                DefaultMutableTreeNode childNode = 
                        new DefaultMutableTreeNode(new FileNode(file));
                node.add(childNode);
                if (file.isDirectory()) {
                    createChildren(file, childNode);
                }
            }
        }

    }

    public class FileNode {

        private File file;

        public FileNode(File file) {
            this.file = file;
        }

        @Override
        public String toString() {
            String name = file.getName();
            if (name.equals("")) {
                return file.getAbsolutePath();
            } else {
                return name;
            }
        }
    }

}

Answer 2

This is how I solved the problem when i encountered it for my project which involved a jtree to show results of my scan.

scanner function is used to initialise the parameters and call the displayDirectoryContents function

Here are some drawbacks of the method i used

• It shows empty folders as leaf nodes instead of showing them as a leaf with no children

• The model should be manually cleared by right clicking on the properties and clearing the model

  Function used

public void displayDirectoryContents(File dir, DefaultMutableTreeNode root2)
       throws InterruptedException {

    DefaultMutableTreeNode newdir = new DefaultMutableTreeNode();

    // creates array of file type for all the files found
    File[] files = dir.listFiles();

    for (File file : files) {
        if (file == null) {
            System.out.println("NUll directory found ");
            continue;
        }
        if (file.isDirectory()) {
            // file is a directory that is a folder has been dound

            if (file.listFiles() == null) {
                // skips null files
                continue;
            }

            // gets the current model of the jtree
            DefaultTreeModel model = (DefaultTreeModel) result.getModel();

            // gets the root
            DefaultMutableTreeNode root = (DefaultMutableTreeNode) model.getRoot();

            // generates a node newdir using filename
            newdir = new DefaultMutableTreeNode(file.getName());

            // adds a node to the root of the jtree
            root2.add(newdir);

            // refresh the model to show the changes
            model.reload();

            // recursively calls the function again to explore the contents
            // folder
            displayDirectoryContents(file, newdir);
        } else {
            // Else part File is not a directory

            // gets the current model of the tree
            DefaultTreeModel model = (DefaultTreeModel) result.getModel();

            // selected node is the position where the new node will be
            // inserted
            DefaultMutableTreeNode selectednode = root2;

            DefaultMutableTreeNode newfile = new DefaultMutableTreeNode(file.getName());

            // inserts a node newfile under selected node which is the root
            model.insertNodeInto(newfile, selectednode, selectednode.getChildCount());

            // refresh the model to show the changes
            model.reload();

        }

    }
}

Scanner Function to initialise the above function

public void scanner() throws InterruptedException {
    // creates a file with the location filename
    String location = "C:\\Users\\Ashish Padalkar\\Documents";
    File currentDir = new File(location);

    // result is the variable name for jtree
    DefaultTreeModel model = (DefaultTreeModel) result.getModel();
    // gets the root of the current model used only once at the starting
    DefaultMutableTreeNode root = (DefaultMutableTreeNode) model.getRoot();
    // function caled
    displayDirectoryContents(currentDir, root);
}