Why my JTree always collasped after refreshing?

[lmsook10]

Hello,
I have been spending whole day trying to figure out why my JTree always collasped after refreshing, but I haven't got any fruit.


I have a Tree and it is collasped in the beginning, and I can expand and do some work(adding nodes or deleting nodes - no problem)
But there is a button which validates the tree, and if a node has problem, its background changes which part is working Okay.
but the tree always goes back to collasped(original state)

I tried every methods that I searched, but nothing is working.

Below is the codes..

Code:

private void validateManifest() {
       	CP_EditorHandler.checkManifestErrors(_contentPackage, false);
        ManifestTree manifestTree = _manifestPanel.getManifestTree();
	// get the selected node before updating
        ManifestTreeNode selectedNode = (ManifestTreeNode) manifestTree.getSelectedNode();
	// get the selected path before updating
 
        TreePath selectedPath = (TreePath) manifestTree.getSelectionPath();
	// below code is the part that recreates nodes of the tree and updates nodes' background
        manifestTree.getModel().setContentPackage(_contentPackage);

	// I set below code to expand to selected path
        manifestTree.setExpandsSelectedPaths(true);
 
	// I even added this code to make it sure
        manifestTree.setExpandedState(selectedPath, true);
}

I even added addTreeWillExpandListener in the tree constructor, but it doesn't work either.

Code:

    	addTreeWillExpandListener
  	  (new TreeWillExpandListener() {
  	    public void treeWillExpand(TreeExpansionEvent e) { }
  	    public void treeWillCollapse(TreeExpansionEvent e)
  	         throws ExpandVetoException {
  	     throw new ExpandVetoException(e, "you can't collapse this JTree");
  	     }
  	    });

What did I do wrong or what should I do to make it work?

I really appreciate your help.

[hardwired]

Code:

import java.awt.*;
import java.util.Enumeration;
import javax.swing.*;
import javax.swing.tree.*;

public class TreeExpansionTest {
    private JScrollPane getContent() {
        JTree tree = new JTree();
        expand(tree, tree.getPathForRow(0));
        return new JScrollPane(tree);
    }

    private void expand(JTree tree, TreePath path) {
        TreeNode node = (TreeNode)path.getLastPathComponent();
        if (node.getChildCount() > 0) {
            Enumeration e = node.children();
            while(e.hasMoreElements()) {
                TreeNode n = (TreeNode)e.nextElement();
                expand(tree, path.pathByAddingChild(n));
            }
        }
        tree.expandPath(path);
    }

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new TreeExpansionTest().getContent());
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}

[lmsook10]

Now I got it work thanks to your codes sample.
Thanks a lot!!