Expansion and Collapse Events in a JTree are fired before a node is expanded or collapsed can be vetoed, thereby preventing the operation. : JTree « Swing « Java Tutorial

1. Java Tutorial
2. Swing
3. JTree

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeExpansionEvent;
import javax.swing.event.TreeExpansionListener;
import javax.swing.event.TreeWillExpandListener;
import javax.swing.tree.ExpandVetoException;
import javax.swing.tree.TreePath;

public class Main {
  public static void main() {
    JTree tree = new JTree();
    tree.addTreeWillExpandListener(new MyTreeWillExpandListener());
    tree.addTreeExpansionListener(new MyTreeExpansionListener());

    JFrame f = new JFrame();
    f.add(new JScrollPane(tree));
    f.setSize(300, 300);
    f.setVisible(true);

  }
}

class MyTreeWillExpandListener implements TreeWillExpandListener {
  public void treeWillExpand(TreeExpansionEvent evt) throws ExpandVetoException {
    JTree tree = (JTree) evt.getSource();

    TreePath path = evt.getPath();
    boolean veto = false;
    if (veto) {
      throw new ExpandVetoException(evt);
    }
  }

  public void treeWillCollapse(TreeExpansionEvent evt) throws ExpandVetoException {
    JTree tree = (JTree) evt.getSource();

    TreePath path = evt.getPath();
    boolean veto = false;
    if (veto) {
      throw new ExpandVetoException(evt);
    }
  }
}

class MyTreeExpansionListener implements TreeExpansionListener {
  public void treeExpanded(TreeExpansionEvent evt) {
    JTree tree = (JTree) evt.getSource();

    TreePath path = evt.getPath();
    System.out.println("treeExpanded");
  }

  public void treeCollapsed(TreeExpansionEvent evt) {
    JTree tree = (JTree) evt.getSource();

    TreePath path = evt.getPath();
    System.out.println("treeCollapsed");
  }
}

14.66.JTree
	14.66.1.	Creating a JTree
	14.66.2.	Using Vector to store JTree values
	14.66.3.	Create JTree from Vector
	14.66.4.	Working with the Nodes of the Tree
	14.66.5.	Scrolling Trees: public void scrollPathToVisible(TreePath path) and public void scrollRowToVisible(int row)
	14.66.6.	Traversing Trees
	14.66.7.	JTree.lineStyle client property
	14.66.8.	Changing the icons of a tree: UIManager.put(Tree.openIcon, new ImageIcon(yourFile.gif));
	14.66.9.	Produce horizontal lines between level-one nodes
	14.66.10.	Using Boolean value cell renderer to display boolean and non-boolean values
	14.66.11.	Creating DefaultTreeCellEditor from its Default Tree Renderer
	14.66.12.	Adding children DefaultMutableTreeNode to its parent
	14.66.13.	JTree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION)
	14.66.14.	Traveling to all the nodes
	14.66.15.	JTree.DynamicUtilTreeNode Class
	14.66.16.	Tree Will Expand Listener
	14.66.17.	To find out when a tree node has been expanded or collapsed
	14.66.18.	Dynamic Tree
	14.66.19.	Have the row height for each row computed individually
	14.66.20.	Setting the Row Height of a JTree
	14.66.21.	All rows will be given 15 pixels of height
	14.66.22.	Preventing Expansion or Collapse of a Node in a JTree: override JTree.setExpandedState()
	14.66.23.	Listening for Expansion and Collapse Events in a JTree Component
	14.66.24.	Expansion and Collapse Events in a JTree are fired before a node is expanded or collapsed can be vetoed, thereby preventing the operation.
	14.66.25.	Creating a JTree Component
	14.66.26.	Visiting All the Nodes in a JTree Component
	14.66.27.	Traverse all expanded nodes in tree
	14.66.28.	Finding a Node in a JTree Component
	14.66.29.	Search backward from last visible row looking for any visible node whose name starts with prefix.
	14.66.30.	Find the path regardless of visibility that matches the specified sequence of names
	14.66.31.	Preventing the Expansion or Collapse of a Node in a JTree Component
	14.66.32.	Have a popup attached to a JTree
	14.66.33.	Adding editable nodes to JTree
	14.66.34.	Drag and drop of a group of files into a tree
	14.66.35.	JTree Look and Feel