Question

I’m using a JTree that is populated from a database.

The tree is created by setting the root node and its childs with custom objects this way:

private DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode("Categorias");
...
ResultSet primaryCategories = dbm.fetchAllCategories();
while (primaryCategories.next()){
    Category category = new Category(primaryCategories.getLong("_id"), 
            primaryCategories.getString("category"));
    DefaultMutableTreeNode childNode = new DefaultMutableTreeNode(category);
    rootNode.add(childNode);

    ResultSet currentSubcategory = dbm.fetchChildSubcategories(category.getCatId());
    while (currentSubcategory.next()){
        Category subcategory = new Category(currentSubcategory.getLong("_id"), 
                currentSubcategory.getString("category"));
        childNode.add(new DefaultMutableTreeNode(subcategory, false));
    }
}
...

After this, the tree is perfectly created. Populated with “Category” Objects, every object has its own ID number and its name to use in toString() method.

The problem comes when it’s set editable. Once the node is renamed, the Category node is also converted into a String Object, so I cant update the new Category name value to the database.

I’ve tried to capture the renaming event with treeNodesChanged(TreeModelEvent e) but, the userObject is already changed to a String Object, and can’t get a referece of what object was edited.

What way can I solve this? Should I have a copy of the tree that’s shown and another of the downloaded from the database and uptade both everytime a change occurs?

*PD: *
I also tried to capture the changed node from the model overriding the method:

public void nodeChanged(TreeNode newNode) {
   DefaultMutableTreeNode parent = ((DefaultMutableTreeNode)newNode.getParent());
    int index = getIndexOfChild(parent, newNode);
    DefaultMutableTreeNode oldNode = (DefaultMutableTreeNode) getChild(parent, index);
    System.out.println(parent.getUserObject().getClass().toString());
    System.out.println(oldNode.getUserObject().getClass().toString());          
}

this prints:

class com.giorgi.commandserver.entity.Category
class java.lang.String

So the old node here has already been changed to a String and I’ve lost completely the reference to the older Category and its ID so I cannot update it in the database.

Any help is wellcome.

Answer 1

Okay, that took a bit of digging.

Basically, when the editing is “stopped”, the JTree will request the editor’s value via editor’s getCellEditorValue. This is then passed to the model via the valuesForPathChanged method, which finally calls the node’s setUserObject method.

Presumably, you are using either the default editor or one based on text field. This will return a String value.

What you need to do is trap the change to the setUserObject method of your tree node, access the value coming (ie, check if it’s a String or not) and update as required.