Thread: JTrees are a nightmare!

Hi,

I've been messing around with JTrees recently and I'm finding it rather difficult to get them to work the way I want. Firstly is to do with being able to rename nodes; I had it working at one point but not anymore.

Here is a very simplified example of the problem:

package gui;
 
import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.UIManager;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.TreeModelListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeSelectionModel;
 
public class TreeFrame extends JFrame implements TreeModelListener {
 
	public TreeFrame() {
 
		setSize(400, 300);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
 
		DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode(
				"Root Node");
		rootNode.add(new DefaultMutableTreeNode("1"));
		rootNode.add(new DefaultMutableTreeNode("2"));
		rootNode.add(new DefaultMutableTreeNode("3"));
		DefaultTreeModel treeModel = new DefaultTreeModel(rootNode);
		treeModel.addTreeModelListener(this);
 
		JTree tree = new JTree(treeModel);
		tree.setEditable(true);
		tree.setShowsRootHandles(true);
 
		add(tree);
		setVisible(true);
 
	}
 
	public static void main(String[] args) {
		try {
			UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
		} catch (Exception e) {
			System.out.println("Failed to load system look and feel.");
		}
		TreeFrame frame = new TreeFrame();
	}
 
	public void treeNodesChanged(TreeModelEvent e) {
		DefaultMutableTreeNode node;
		node = (DefaultMutableTreeNode) (e.getTreePath().getLastPathComponent());
		/*
		 * If the event lists children, then the changed node is the child of
		 * the node we have already gotten. Otherwise, the changed node and the
		 * specified node are the same.
		 */
		try {
			int index = e.getChildIndices()[0];
			node = (DefaultMutableTreeNode) (node.getChildAt(index));
		} catch (NullPointerException exc) {
		}
 
		System.out.println("The user has finished editing the node.");
		System.out.println("New value: " + node.getUserObject());
	}
 
	public void treeNodesInserted(TreeModelEvent e) {
	}
 
	public void treeNodesRemoved(TreeModelEvent e) {
	}
 
	public void treeStructureChanged(TreeModelEvent e) {
	}
 
}

Most of this is taken straight from Oracle's "How to Use Trees" guide. But basically this demonstrates the problem - click on a node, press "F2" and you can type in a name, but the name doesn't stay!

Does anyone know how to fix this so the nodes can be properly renamed?

Thanks,

- Danjb

Wow, that's really weird... I could have sworn it didn't work the other day! Perhaps I was clicking on another node instead of pressing "Enter".

I have a second problem, however, regarding sorting nodes:

Whenever I add or rename a node, I want the nodes to remain sorted alphabetically; just to complicate things further, however, I have 2 types of node, "Files" and "Folders", and I want "Folders" to always come first.

This is my sorting code, but I get some very strange results, such as disappearing nodes or even nodes showing up as just "...":

    /**
     * Sorts all the nodes in the tree
     * First by: "Folder" Status
     * Then: Alphabetically
     */
    public void sortNodes(TreeItem folder){
    	Enumeration<TreeItem> children = folder.children();
    	while (children.hasMoreElements()){
    		TreeItem node = children.nextElement();
    		sortNodes(node);
    		if (!node.isLeaf()) sortChildren(node);
    	}
    }
 
    /**
     * Sorts the children in a folder
     * First by: "Folder" Status
     * Then: Alphabetically
     * @param parent Folder TreeItem containing children
     */
    public void sortChildren(TreeItem parent){
    	ArrayList<TreeItem> folders = new ArrayList<TreeItem>();
		ArrayList<TreeItem> files = new ArrayList<TreeItem>();
		// Use Enumeration children()
		for (int j = 0; j < parent.getChildCount(); j++){
			TreeItem child = (TreeItem)parent.getChildAt(j);
			if (child.isFolder()){
				folders.add(child);
			} else {
				files.add(child);
			}
		}
		Collections.sort(folders);
		Collections.sort(files);
		parent.removeAllChildren();
		for (TreeItem child : folders){
			parent.add(child);
		}
		for (TreeItem child : files){
			parent.add(child);
		}
    }

Any help would be appreciated,

Thanks,

- Danjb

Does anyone know how I can fix this?