Trail: Creating a GUI With JFC/Swing
Lesson: Writing Event Listeners
Section: Implementing Listeners for Commonly Handled Events
How to Write a Tree Model Listener
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How to Write a Tree Model Listener

By implementing a tree model listener, you can detect when the data displayed by a tree changes. You can use a tree model listener to detect when the user edits tree nodes. All notifications describe changes relative to a node in the tree. For details, read Dynamically Changing a Tree.

The Tree Model Listener API

The TreeModelListener Interface

TreeModelListener has no adapter class.

Method Purpose
treeNodesChanged(TreeModelEvent) Called when one or more sibling nodes have changed in some way.
treeNodesInserted(TreeModelEvent) Called after nodes have been inserted into the tree.
treeNodesRemoved(TreeModelEvent) Called after nodes have been removed from the tree.
treeStructureChanged(TreeModelEvent) Called after the tree's structure has drastically changed from the current node on down. This event applies to all nodes connected to this node.

The TreeModelEvent API

Method Purpose
Object getSource()
(in java.util.EventObject)
Return the object that fired the event.
int[] getChildIndices() For treeNodesChanged, treeNodesInserted, and treeNodesRemoved, returns the indices of the changed, inserted, or deleted nodes, respectively. Returns nothing useful for treeStructureChanged.
Object[] getChildren() Returns the objects corresponding to the child indices.
Object[] getPath() Returns the path to the parent of the changed, inserted, or deleted nodes. For treeStructureChanged, returns the path to the node beneath which the structure has changed.
TreePath getTreePath() Returns the same thing as getPath, but as a TreePath object.

Examples that Use Tree Model Listeners

The following table lists the examples that use tree expansion listeners.

Example Where Described Notes
DynamicTreeDemo How to Use Trees The DynamicTree class implements a tree model listener to detect when the user has edited a node's data.

Problems with the examples? Try Compiling and Running the Examples: FAQs.
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