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Thread: JTrees are a nightmare!

  1. #1
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    Default 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


  2. #2
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    Default Re: JTrees are a nightmare!

    Hello Danjb,

    This code works perfectly

    Press F2 or double click the node, enter the new value and press enter. The new value remains!
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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  3. #3
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    Default Re: JTrees are a nightmare!

    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

  4. #4
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    Default Re: JTrees are a nightmare!

    Does anyone know how I can fix this?

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