How to Write a Tree Selection Listener

To detect when the user selects a node in a tree, you need to register a tree selection listener. Here is an example, taken from the TreeDemo example discussed in Responding to Node Selection, of detecting node selection in a tree that can have at most one node selected at a time:

tree.addTreeSelectionListener(new TreeSelectionListener() {

public void valueChanged(TreeSelectionEvent e) {

DefaultMutableTreeNode node = (DefaultMutableTreeNode)

tree.getLastSelectedPathComponent();

/* if nothing is selected */

if (node == null) return;

/* retrieve the node that was selected */

Object nodeInfo = node.getUserObject();

...

/* React to the node selection. */

...

}

});

To specify that the tree should support single selection, the program uses this code:

tree.getSelectionModel().setSelectionMode

(TreeSelectionModel.SINGLE_TREE_SELECTION);

The TreeSelectionModel interface defines three values for the selection mode:

DISCONTIGUOUS_TREE_SELECTION

This is the default mode for the default tree selection model. With this mode, any combination of nodes can be selected.

SINGLE_TREE_SELECTION

This is the mode used by the preceding example. At most one node can be selected at a time.

CONTIGUOUS_TREE_SELECTION

With this mode, only nodes in adjoining rows can be selected.

Running Codes

http://docs.oracle.com/javase/tutorial/uiswing/events/treeselectionlistener.html