# Interface TreeExpansionListener

All Superinterfaces:
  `EventListener`

All Known Implementing Classes:
  `BasicTreeUI.TreeExpansionHandler, JTree.AccessibleJTree`

public interface TreeExpansionListener extends EventListener
The listener that's notified when a tree expands or collapses a node. For further documentation and examples see How to Write a Tree Expansion Listener, a section in The Java Tutorial.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `treeCollapsed(TreeExpansionEvent event)`
  Called whenever an item in the tree has been collapsed.
  `void`
  `treeExpanded(TreeExpansionEvent event)`
  Called whenever an item in the tree has been expanded.

- ## Method Details

  - ### treeExpanded

    void treeExpanded(TreeExpansionEvent event)
    Called whenever an item in the tree has been expanded.
    Parameters:
      `event` - a `TreeExpansionEvent` containing a `TreePath` object for the expanded node

  - ### treeCollapsed

    void treeCollapsed(TreeExpansionEvent event)
    Called whenever an item in the tree has been collapsed.
    Parameters:
      `event` - a `TreeExpansionEvent` containing a `TreePath` object for the collapsed node