java JTree not updating

I am having some issues with JTree. When I create my DefaultTreeModel within the same class, the JFrame updated fine. However, I want to call the update method from another class and when I do the JTree remains blank. The JTree is in the class GUI and stored like so in another class called store.

public static GUI UI = new GUI();

...

UI.init();
UI.buildJTree(xml);

However, this does nothing. I however inside the class GUI I call:

buildJTree(xml);

Everything works fine. Does anyone have any ideas as to why there might be a problem?

Build Tree method is as follows:

public void buildTree(String xml) {
    try {
        Console.output("Building tree");
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        InputSource is = new InputSource();
        is.setCharacterStream(new StringReader(XML.wrap(xml.trim())));
        Document doc = db.parse(is);
        NodeList xml_packet = doc.getElementsByTagName("packet");
        NodeList channels = xml_packet.item(0).getChildNodes().item(0).getChildNodes();

        Element start = (Element) xml_packet.item(0).getFirstChild();
        this.status_txt.setText(start.getAttribute("connected") + ", connected.");
        MutableTreeNode root = new DefaultMutableTreeNode(start.getAttribute("server"));

        for (int n = 0; n < channels.getLength(); n++) {
            Element fstElmnt = (Element) channels.item(n);
            Console.output("CHANNEL::" + fstElmnt.getAttribute("name"));
            DefaultMutableTreeNode userss = new DefaultMutableTreeNode(fstElmnt.getAttribute("name"));
            root.insert(userss, n);

            NodeLi开发者_如何学JAVAst users = channels.item(n).getFirstChild().getChildNodes();

            for (int usr = 0; usr < users.getLength(); usr++) {
                userss.insert(new DefaultMutableTreeNode(users.item(usr).getFirstChild().getNodeValue()), usr);
            }
        }


        model = new DefaultTreeModel(root);

        this.trees.setModel(model);

        for (int t = 0; t < this.trees.getRowCount(); t++) {
            this.trees.expandRow(t);
        }

    } catch (Exception e) {
        e.printStackTrace();
    }

}

Many Thanks in advance.

There's too little information in your question to be sure, but it's possible that you're running afoul of the requirement that all Swing-mutating work must be done in the event thread.

So, for example:

final Runnable swingTask = new Runnable() {
    public void run() {
        UI.init();
        UI.buildJTree(xml);
    }
};
if (EventQueue.isDispatchThread()) {
    swingTask.run();
} else {
    EventQueue.invokeAndWait(swingTask);
}