# Class BasicTreeUI.TreeExpansionHandler

java.lang.Object
javax.swing.plaf.basic.BasicTreeUI.TreeExpansionHandler

All Implemented Interfaces:
  `EventListener, TreeExpansionListener`

Enclosing class:
  `BasicTreeUI`

public class BasicTreeUI.TreeExpansionHandler extends Object implements TreeExpansionListener
Updates the TreeState in response to nodes expanding/collapsing.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `TreeExpansionHandler()`
  Constructs a `TreeExpansionHandler`.

- ## 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.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### TreeExpansionHandler

    public TreeExpansionHandler()
    Constructs a `TreeExpansionHandler`.

- ## Method Details

  - ### treeExpanded

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

  - ### treeCollapsed

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