I am looking for a way to select the TreeNode before the actually selected node (if no Node is selected, the first Node AFTER the root should be selected) on Button click. I am basically having a Hashtable ht and a JTree filled with nodes (all Nodes allowing Children). Once i click a node, i want to look up in the Hashtable for that Object and the system should write something like "You selected the 'Object.name'". Then the user should be able to click a JButton and select the node before the clicked node. Of course there should also be this line with an updated 'Object.name'. Maybe there is even a way to update the GUI of the tree, so that the other TreeNode is shown as selected.
I have been trying around for quite a while with the treePath-Methods of the selectionModel and the TreeNodes (e.g. saving them in Lists and trying to select the Element before), but nothing seems to work. I am also not finding anything useful on Google or StackOverflow. I was thinking that it might work somehow with the getPreviousSibling-Method from the DefaultMutableTreeNode?
Last thing I tried:
DefaultMutableTreeNode treeNode = new DefaultMutableTreeNode();
treeNode = (DefaultMutableTreeNode) getLastSelectedPathComponent();
setSelectionPath(new TreePath(((DefaultTreeModel) treeModel).getPathToRoot(treeNode.getPreviousSibling())));
Unfortunately I keep getting a NullPointerException:
in line 2 of this snippet (although I selected another TreeNode before, wich has a sibling before).
Can anyone please tell me what I did wrong or tell me what other way might work? :D If you need more information please have no regard in asking me.
