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Answer 1

A:

You need to ensure that after updating your model you instruct it to fire an event to cause any registered listeners to be notified of the event. One of the listeners will be the JTree and upon receiving the event it will repaint.

For example, DefaultTreeModel contains the methods:

nodeChanged nodesChanged nodeStructureChanged nodesWereInserted nodesWereRemoved

Also, as with all Swing programming you need to ensure you are updating your model on the Event Dispatch Thread.

Adamski 2010-09-29 13:04:25

You don't have to fire these events off yourself. All you have to do is update the model by calling the `insertNodeInto` method, for example, and let the model take care of firing events to the TreeModelListeners.

dogbane 2010-09-29 13:28:52

Good point, although in some cases it would be better to manage it yourself. For example, if I wanted to add 1000 child nodes I would not wish to fire 1000 "nodes were added" events.

Adamski 2010-09-29 14:13:11

Thank you Sir! But these methods you mentioned are private and couldn't be accessed.

sajad 2010-09-30 12:43:41

You're absolutely right! I've changed my answer to reflect the correct public methods you should be calling.

Adamski 2010-10-05 16:27:47

Answer 2

+1 A:

In addition to the insertNodeInto suggestion you can also use:

DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
DefaultMutableTreeNode root = (DefaultMutableTreeNode)model.getRoot();
root.add(new DefaultMutableTreeNode("another_child"));
model.reload(root);

camickr 2010-09-29 16:43:17

So thank you for your worthy answer ! Every time I want to update my tree I use this method.

sajad 2010-09-30 12:42:16

This will work but is a "brute force" approach when dealing with large trees. For example, if I were to loop and add 1000 nodes to a tree already containing 50,000 items this would be very inefficient.

Adamski 2010-10-05 16:30:39

Answer 3

A:

Do you mean the GUI aspect just isn't showing your change? You should probably look int repaint() and revalidate().

Here's a good description of when to call which one.

Bryan 2010-09-29 16:48:39

Yes calling this methods are necessary.

sajad 2010-09-30 12:44:33

-1, No repaint() and revalidate() are not necessary. When you udpate the model the model is responsible for notifying the view of the change so the tree can repaint itself.

camickr 2010-09-30 14:42:23

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updating JTree in java GUI

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