Java™ Platform
Standard Ed. 6

javax.swing.tree
Interface TreeModel

All Known Implementing Classes:
DefaultTreeModel

public interface TreeModel

The model used by JTree.

JTree and its related classes make extensive use of TreePaths for indentifying nodes in the TreeModel. If a TreeModel returns the same object, as compared by equals, at two different indices under the same parent than the resulting TreePath objects will be considered equal as well. Some implementations may assume that if two TreePaths are equal, they identify the same node. If this condition is not met, painting problems and other oddities may result. In other words, if getChild for a given parent returns the same Object (as determined by equals) problems may result, and it is recommended you avoid doing this.

Similarly JTree and its related classes place TreePaths in Maps. As such if a node is requested twice, the return values must be equal (using the equals method) and have the same hashCode.

For further information on tree models, including an example of a custom implementation, see How to Use Trees in The Java Tutorial.

See Also:
TreePath

Method Summary
 void addTreeModelListener(TreeModelListener l)
          Adds a listener for the TreeModelEvent posted after the tree changes.
 Object getChild(Object parent, int index)
          Returns the child of parent at index index in the parent's child array.
 int getChildCount(Object parent)
          Returns the number of children of parent.
 int getIndexOfChild(Object parent, Object child)
          Returns the index of child in parent.
 Object getRoot()
          Returns the root of the tree.
 boolean isLeaf(Object node)
          Returns true if node is a leaf.
 void removeTreeModelListener(TreeModelListener l)
          Removes a listener previously added with addTreeModelListener.
 void valueForPathChanged(TreePath path, Object newValue)
          Messaged when the user has altered the value for the item identified by path to newValue.
 

Method Detail

getRoot

Object getRoot()
Returns the root of the tree. Returns null only if the tree has no nodes.

Returns:
the root of the tree

getChild

Object getChild(Object parent,
                int index)
Returns the child of parent at index index in the parent's child array. parent must be a node previously obtained from this data source. This should not return null if index is a valid index for parent (that is index >= 0 && index < getChildCount(parent)).

Parameters:
parent - a node in the tree, obtained from this data source
Returns:
the child of parent at index index

getChildCount

int getChildCount(Object parent)
Returns the number of children of parent. Returns 0 if the node is a leaf or if it has no children. parent must be a node previously obtained from this data source.

Parameters:
parent - a node in the tree, obtained from this data source
Returns:
the number of children of the node parent

isLeaf

boolean isLeaf(Object node)
Returns true if node is a leaf. It is possible for this method to return false even if node has no children. A directory in a filesystem, for example, may contain no files; the node representing the directory is not a leaf, but it also has no children.

Parameters:
node - a node in the tree, obtained from this data source
Returns:
true if node is a leaf

valueForPathChanged

void valueForPathChanged(TreePath path,
                         Object newValue)
Messaged when the user has altered the value for the item identified by path to newValue. If newValue signifies a truly new value the model should post a treeNodesChanged event.

Parameters:
path - path to the node that the user has altered
newValue - the new value from the TreeCellEditor

getIndexOfChild

int getIndexOfChild(Object parent,
                    Object child)
Returns the index of child in parent. If either parent or child is null, returns -1. If either parent or child don't belong to this tree model, returns -1.

Parameters:
parent - a node in the tree, obtained from this data source
child - the node we are interested in
Returns:
the index of the child in the parent, or -1 if either child or parent are null or don't belong to this tree model

addTreeModelListener

void addTreeModelListener(TreeModelListener l)
Adds a listener for the TreeModelEvent posted after the tree changes.

Parameters:
l - the listener to add
See Also:
removeTreeModelListener(javax.swing.event.TreeModelListener)

removeTreeModelListener

void removeTreeModelListener(TreeModelListener l)
Removes a listener previously added with addTreeModelListener.

Parameters:
l - the listener to remove
See Also:
addTreeModelListener(javax.swing.event.TreeModelListener)

Java™ Platform
Standard Ed. 6

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