Changing the tree in JTree?

Posted on 2001-06-12
Last Modified: 2010-08-05
I'm using Forte IDE and added a JTree via drag and drop.

It creates a default tree so now I want to change it.
the problem is that all the samples I have uses the following code:

DefaultMutableTreeNode root = new DefaultMutableTreeNode( "Top" );

DefaultMutableTreeNode col21 = new DefaultMutableTreeNode ("Line1" );


DefaultMutableTreeNode col22 = new DefaultMutableTreeNode ("line2" );


JTree tree = new JTree( root );

The problem is that Forte creates the instance of JTree already and its readonly since this is the part that the ide uses.  So I cant create the tree when creating a new instance of the tree.

Is there another way of doing this?  Maybe a different method?

Question by:eric07
  • 3
  • 2

Expert Comment

ID: 6184947

In the declarations you want to write:

  DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
  TreePath tp = null;
  JTree jTree1 = new JTree(root);

This creates a root node and assigns it to the JTree (like you have done).

Below is a method which is called when an add button is pressed by the mouse.  It takes a string from a JTextField (addTextField) and adds a def. mut. tree node to the selected node - from the tree.

  void addButton_mouseClicked(MouseEvent e)
    if(addTextField.getText().length() > 0)
        //create def. mut. tree node
          //and add text to it
          DefaultMutableTreeNode dMTN = new DefaultMutableTreeNode(addTextField.getText());
        //create a treepath and assign the selected path
          //from the JTree (the path that is currently selected)
          TreePath myTreePath = jTree1.getSelectionPath();

          //Obtain the last def. mut. tree node from the tree
          //and assign it to Temp
        DefaultMutableTreeNode temp = (DefaultMutableTreeNode)myTreePath.getLastPathComponent();
        //Add the new Def. mut. tree node to temp
          //Update the tree
          //Clear the text field.
        addTextField.setText(new String());
      catch(Exception ee)
        JOptionPane.showMessageDialog(this, "No Node is selected.\nPlease select then press the 'Add' button.");

      JOptionPane.showMessageDialog(this, "No data entered!\nPlease try again!");


This code is taken from a small Swing applet that I have created, if you want the code, html file and everything, provide your e-mail address!

I hope this helps.


Author Comment

ID: 6187236
What about this problem though.

Since Forte already did a new on the JTree control.
and now your code wants me to do a another new.  Isnt that creating another instance of the control?  And if so is that ok?

JTree tree = new JTree( root );

The problem is that Forte creates the instance of JTree already and its readonly since this is the part
that the ide uses.  So I cant create the tree when creating a new instance of the tree.

Expert Comment

by:Igor Bazarny
ID: 6189082

Create you data as DefaultTreeModel and set it using JTree.setModel().
Or take existing model using getModel() (It will amost certainly be
DefaultTreeModel with DefaultMutableTreeNodes inside) and modify it.

Igor Bazarny
Brainbench MVP for Java 1
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Author Comment

ID: 6189230
Do you happen to have a sample on how to do this.  Excuse my ignorance since i'm new to this.


Accepted Solution

Igor Bazarny earned 50 total points
ID: 6193407
OK, can you find a place in code where you want to update model? I'm not familiar with code generated by Forte. There should be init method or something like. At that place you can create your model:

    DefaultMutableTreeNode root = new DefaultMutableTreeNode("root");
    root.add(new DefaultMutableTreeNode("child1"));
    root.add(new DefaultMutableTreeNode("child2"));

    DefaultTreeModel model = new DefaultTreeModel(root);

And show that model in JTree:


Igor Bazarny

Author Comment

ID: 6193916
Thanks allot bazarny you really helped me.  I totally missed setModel() member function.  That did the trick

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