Dont collapse JTree after refresh?

[Max Power]

hello, is it somehow possible to save the expansion state of a jtree? the tree
collpases everytime i use the tree.setmodel method to refresh it....any ideas?

thank you :-)

[slade cox]

First I would say that you are using TreeModel incorrectly if you are modifying the JTree by calling setModel. This should only be used for creating a new JTree. Instead you should modify your TreeModel and call the reload() method of DefaultTreeModel (which you extended, right?). For a full description and example see:

http://java.sun.com/products/jfc/tsc/articles/jtree/

If you absolutely insist on using the setModel method to update your tree then you could do something like this. Keep track of the expanded paths in a list. Register a TreeExpansionListener that does something like this:

myJTree.addTreeExpansionListener(new TreeExpansionListener() {
  public void treeCollapsed(TreeExpansionEvent e) {
    myPathList.remove(e.getPath());
  }
  public void treeExpanded(TreeExpansionEvent e) {
    myPathList.add(e.getPath());
  }
});

Then after calling setModel iterate through the path list and call expandPath for each one. But, the first option is better.

[Max Power]

hi, thanks :-). i am implementing treemodel, can i use your first option anyway?

thanks

[slade cox]

Yes you can. On the page mentioned above see the FileExplorer example and the Dynamically Modifying a Tree section.

[Max Power]

hi again. i tried your second suggestion without success. :-( here is my example:

 
import javax.swing.*;
import javax.swing.tree.TreeModel;
import javax.swing.tree.TreePath;
import javax.swing.event.TreeModelListener;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.EventListenerList;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.*;
import java.util.HashMap;
import java.io.File;
import java.io.Serializable;
import javax.swing.tree.*;
import javax.swing.event.*; 
 

public class FileTreeModel implements TreeModel, Serializable, Cloneable {
protected EventListenerList listeners;
 
private Map map;
 
private File root;
 
static ArrayList myPathList = new ArrayList();
 
public FileTreeModel(File root) {
if (!root.exists())
throw new IllegalArgumentException(String.valueOf(root));
 
this.root = root;
 
this.listeners = new EventListenerList();
 
this.map = new HashMap();
}
 
public Object getRoot() {
return root;
}
 
public boolean isLeaf(Object node) {

return !((File) node).isDirectory();
}
 
public int getChildCount(Object node) {
List children = children(node);
 
if (children == null)
return 0;
 
return children.size();
}
 
public Object getChild(Object parent, int index) {
return children(parent).get(index);
}
 
public int getIndexOfChild(Object parent, Object child) {
return children(parent).indexOf(child);
}
 
public void valueForPathChanged(TreePath path, Object value) {
}
 
protected List children(Object node) {
File f = (File) node;
 
if (!f.isDirectory())
return null;
 
List children = (List) map.get(f);
 
if (children == null) {
File[] c = f.listFiles();
 
if (c == null)
return null;
 
children = new ArrayList(c.length);
 
for (int len = c.length, i = 0; i < len; i++)
children.add(c[i]);
 
map.put(f, children);
}
 
return children;
}
 
public Object clone() {
try {
FileTreeModel clone = (FileTreeModel) super.clone();
 
clone.listeners = new EventListenerList();
 
return clone;
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
}

 
//HAB ICH SCHON!!
public void addTreeModelListener(TreeModelListener l) {
listeners.add(TreeModelListener.class, l);
}
 
public void removeTreeModelListener(TreeModelListener l) {
listeners.remove(TreeModelListener.class, l);
}

public static void main(String[] args) {
if (args.length != 1) {
System.err.println("Usage: java FileTreeModel path");
System.exit(1);
}
 
File root = new File(args[0]);
 
if (!root.exists()) {
System.err.println(root + ": No such file or directory");
System.exit(2);
}
 
JTree t = new JTree(new FileTreeModel(root));
 
t.addTreeExpansionListener(new TreeExpansionListener() {
public void treeCollapsed(TreeExpansionEvent e) {
myPathList.remove(e.getPath());
}

public void treeExpanded(TreeExpansionEvent e) {
myPathList.add(e.getPath());
}
});
 
//t.setCellRenderer(new Renderer());
JFrame f = new JFrame(root.toString());
 
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
f.getContentPane().add(new JScrollPane(t));
 
f.pack();
f.setVisible(true);
try{
Thread.sleep(5000);
}catch(Exception te){
}

System.out.println("Calling...");
t.setModel(new FileTreeModel(root));

TreePath tpa = null;
for(int li=0;li<myPathList.size();li++){
String test=myPathList.get(li).toString();
test=test.replaceAll("^\\[", "");
test=test.replaceAll("\\]$", "");
tpa= new TreePath(test);

System.out.println("expanding: " + tpa);
t.expandPath(tpa);
//System.out.println("test: " + tpa);

    
 
}

/*for (Iterator it=myPathList.iterator(); it.hasNext(); ) {
String test=it.next().toString();
test=test.replaceAll("^\\[", "");
test=test.replaceAll("\\]$", "");
tpa= new TreePath(test);
t.expandPath(tpa);
System.out.println("test: " + tpa);

}
*/
}
}
 

after 5 seconds im trying to expand the paths but i am getting a classcastexception!! can you see why?

THANKS A LOT
[ July 19, 2004: Message edited by: Andreas Golchert ]

[slade cox]

What is the full exception message? ie. which line is causing the ClassCastException, which object is incorrectly cast?

Also, when you iterate through myPathList and expand the paths you could do something simpler like

for(int li=0;li<myPathList.size();li++){
t.expandPath((TreePath)myPathList.get(li));
}

[Max Power]

hi, yeah thats it...tHANKS

[slade cox]

Glad to help. Out of curiosity, how smoothly does the JTree work?