Updating a JTree
Hi, i'm relatively new to java, and i have a question about JTrees. I have created a GUI that uses a JTree with a root and a bunch of leaf nodes. In my program, the user must be able to click a button and add a new leaf node to the JTree. However, I dont know how to update the JTree so that the user can see the new nodes right after he/she clicks the button. Please do not use alot of jargon or condesed code in your replies, or i probably wont understand it. Thanks in advance.
[488 byte] By [
Tommasoa] at [2007-10-2 4:03:10]
To insert a node at the end of the roots children and have the tree update so you are shown it has been added:
DefaultMutableTreeNode root = (DefaultMutableTreeNode)tree.getModel().getRoot();
int childCnt = root.getChildcount();
DefaultMutableTreeNode newChild = new DefaultMutableTreeNode("new last child node");
root.insertNodeInto(newChild,root,childCnt+1);
insertNodeInto automatically calls nodesWereInserted, which then calls fireNodesInserted. These are the methods that update the GUI to reflect your new node in the model.
Thanks for the help, but for some reason i could not get the last line to compile. I also looked it up in the DefaultTreeModel class interface and it looked correct.
root.insertNodeInto(newChild,root,childCnt+1);
here is the error my compiler gives me:
cannot resolve symbol - method insertNodeInto(javax.swing.tree.DefaultMutableTreeNode, javax.swing.tree.DefaultMutableTreeNode, int)
Do i need to import a special class maybe?
Well, for sure you'd need to
import javax.swing.*;
import javax.swing.tree.*;
Also check that the version of javac you're using is more recent. I guess you could be using an old enough version that that particular function may not have existed yet?
Oh sorry, I see it. that method is not part of the node but of the model.
((DefaultTreeModel)tree.getModel()).insertNodeInto(newChild,root,childCnt+1);
I'm not sure if the +1 part will cause an ArrayOutOfBoundException. Give it a shot.
Ok, so the new code compiled, but the program terminates when i click the button to add a new node.
This is the error it Gives Me:
java.lang.ArrayIndexOutOfBoundsException: 4 > 3
at java.util.Vector.insertElementAt(Vector.java:557)
at javax.swing.tree.DefaultMutableTreeNode.insert(DefaultMutableTreeNode.java:177)
at javax.swing.tree.DefaultTreeModel.insertNodeInto(DefaultTreeModel.java:218)
at SuperCrap$clickListener.actionPerformed(SuperCrap.java:183)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1786)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1839)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:245)
at java.awt.Component.processMouseEvent(Component.java:5100)
at java.awt.Component.processEvent(Component.java:4897)
at java.awt.Container.processEvent(Container.java:1569)
at java.awt.Component.dispatchEventImpl(Component.java:3615)
at java.awt.Container.dispatchEventImpl(Container.java:1627)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
at java.awt.Container.dispatchEventImpl(Container.java:1613)
at java.awt.Window.dispatchEventImpl(Window.java:1606)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
