Module java.desktop
Package 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 identifying 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 Details

    • 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
      index - index of child to be returned
      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)