Problem with jtree selection

Question

Hi all,
I've got a JTree that represents a sort of data that I'm going to change dynamically in my application. I'd like to reset the selection of the user to the leaf she has selected before the change to the tree structure.
First of all my tree uses DefaultMutableTreeNode to build each node, and each DefaultMutableTreeNode contains a SingleKeyValue object, that is a key-value object (two strings) and that has an hashcode defined as follows:
public class SingleKeyValue extends BaseKeyValue{
      * The key of the database object.
     protected String key = null;
      * The description of this object.
     protected String value = null;
     public int hashCode() {
          return this.key.hashCode();
     I hope the hashcode can help me finding the right object even when its value changes (but the key is the same). The construction of the tree is the following:
DefaultMutableTreeNode root = new DefaultMutableTreeNode("The root");
// iterate and build each node
SingleKeyValue object = new SingleKeyValue("key","value");
DefaultMutableTreeNode node = new DefaultMutableTreeNode(object);
root.add(node);
DefaultTreeModel model = new DefaultTreeModel(root);
JTree  tree = new JTree(model);             
            so the tree is associated to a DefaultTreeModel. Then, when I need to change something in the tree I rebuild the tree and all leafs (with the SingleKeyValues) and rebuild the model:
          TreeModel treeModel = this.myTree.getModel();
          TreeSelectionModel selectionModel = this.myTree.getSelectionModel();
          DefaultTreeModel defaultTreeModel = null;
          DefaultTreeSelectionModel defaultTreeSelectionModel = null;
          TreePath selectedPath = null;
          TreeNode root = null;
          Logger.info("SimpleTreePanel.refreshDatabaseView: treemodel "+treeModel + " selectionModel " + selectionModel);
          if( treeModel != null && treeModel instanceof DefaultTreeModel ) {
               defaultTreeModel = (DefaultTreeModel) treeModel;
               root = this.getRoot();
               // get the selection
               if( selectionModel != null && selectionModel instanceof DefaultTreeSelectionModel ){
                    defaultTreeSelectionModel = (DefaultTreeSelectionModel) selectionModel;
                    selectedPath = defaultTreeSelectionModel.getSelectionPath();
                    Logger.warn("Selection path of the tree: "+selectedPath);
               // rebuild the tree
               defaultTreeModel.setRoot(root);
               // set the selected element
               defaultTreeSelectionModel.setSelectionPath(selectedPath);The problem is that after the above code the tree is all closed, no leaf are selected. I guess the problem is with the SingleKeyValueObject because I've tried the default model and it works with, for example, simple strings. Any idea about?
Thanks,
Luca

Answer 1

Here's a complete test program that creates a few SingleKeyValue objetcs (objects with a key and a description) and that then places them into a JTree using the DefaultMutableTreeNode. After that, the selection of user is took and one node is changed, but while the selection is working, the reload/refresh of the tree is not.
Any idea about how to work on it?
public class SingleKeyValue extends BaseKeyValue{
      * The key of the database object.
     protected String key = null;
      * The description of this object.
     protected String value = null;
     // constants related to the type of the table this object refers to
     public static final String COMPETENCE = "competenza";
     public static final String FAMILY            = "famiglia_competenza";
     public static final String ROLE              = "ruolo";
     public static final String PROVINCE      = "provincia";
     public static final String KNOWLEDGE  = "titolo_studio";
     public final static String OBJECTIVE      = "obiettivo";
     public final static String PERSON         = "persona";
     public SingleKeyValue( String key, String value, String table){
          super();
          this.key = key;
          this.value = value;
          this.SQLTable = table;
      * @return the key
     public final String getKey() {
          return key;
      * @param key the key to set
     public final void setKey(String key) {
          this.key = key;
      * @return the value
     public final String getValue() {
          return value;
      * @param value the value to set
     public final void setValue(String value) {
          this.value = value;
      * Shows this element.
     public String toString(){
          String ret;
          if( this.showKey ){
               ret =  this.label + this.key +" { "+ this.value +" }";
          else
               ret = this.label + this.value;
          // trim the string
          if( ret.length() > this.maxLength )
               return ret.substring(0 , this.maxLength);
          else
               return ret;
      * The hash code of this object is the hash code of the key.
      * @return the hash code of the key of the object
     public int hashCode() {
          return this.key.hashCode();
      * Returns true if the object passed is a single key value equals (i.e., with the same key) of this one.
     public boolean equals(Object o){
          if( o== null || (! (o instanceof SingleKeyValue) ) )     return false;
          else
               return (this.hashCode() == o.hashCode());
     public static void main(String argv[]) throws Exception{
         SingleKeyValue skv1 = new SingleKeyValue("Key1","Description1", SingleKeyValue.COMPETENCE);
         SingleKeyValue skv2 = new SingleKeyValue("Key1a","Description1a", SingleKeyValue.COMPETENCE);
         SingleKeyValue skv3 = new SingleKeyValue("Key1b","Description1b", SingleKeyValue.COMPETENCE);
         SingleKeyValue skv4 = new SingleKeyValue("Key2","Description2", SingleKeyValue.COMPETENCE);
         SingleKeyValue skv5 = new SingleKeyValue("Key2a","Description2a", SingleKeyValue.COMPETENCE);
         SingleKeyValue skv6 = new SingleKeyValue("Key2b","Description2b", SingleKeyValue.COMPETENCE);
         DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode("root");
         DefaultMutableTreeNode node1 = new DefaultMutableTreeNode(skv1);
         DefaultMutableTreeNode node2 = new DefaultMutableTreeNode(skv2);
         DefaultMutableTreeNode node3 = new DefaultMutableTreeNode(skv3);
         DefaultMutableTreeNode node4 = new DefaultMutableTreeNode(skv4);
         DefaultMutableTreeNode node5 = new DefaultMutableTreeNode(skv5);
         DefaultMutableTreeNode node6 = new DefaultMutableTreeNode(skv6);
         rootNode.add(node1);
         node1.add(node2);
         node1.add(node3);
         rootNode.add(node4);
         node4.add(node5);
         node4.add(node6);
         JTree tree = new JTree(rootNode);
         JFrame f = new JFrame("Tree try");
         f.add( new JScrollPane(tree) );
         f.setSize(300,300);
         f.setVisible(true);
         System.out.println("Please select a node within 10 seconds");
         Thread.sleep(10000);
         // now get the user selection
     TreeModel treeModel = tree.getModel();
     TreeSelectionModel selectionModel = tree.getSelectionModel();
     DefaultTreeModel defaultTreeModel = null;
     DefaultTreeSelectionModel defaultTreeSelectionModel = null;
     TreePath selectedPath = null;
     TreeNode root = null;
     if( treeModel != null && treeModel instanceof DefaultTreeModel ) {
          defaultTreeModel = (DefaultTreeModel) treeModel;
          // get the selection
          if( selectionModel != null && selectionModel instanceof DefaultTreeSelectionModel ){
               defaultTreeSelectionModel = (DefaultTreeSelectionModel) selectionModel;
               selectedPath = defaultTreeSelectionModel.getSelectionPath();
          // rebuild the tree
          node1.setUserObject(new SingleKeyValue("key20","key changed",SingleKeyValue.FAMILY));
          defaultTreeModel.reload();
          // set the selected element
          defaultTreeSelectionModel.setSelectionPath(selectedPath);
}