JTree Zustand speichern

Dieses Beispiel zeigt, wie wir den Zustand von einem JTree speichern können, so daß er nach einem Programmneustart wieder geladen werden kann.

<code=java>/*

* TreeStatusDemo.java
* 
* This example shows you how to store the tree status with XMLEncoder
* so that it can be reloaded after program restart.
* Maybe it can help you.
*
* Btw, we can use XMLEncoder not only to store the tree status, but for storing any
* object we like. To do so, it's enough that the objects respect the "Bean" format,
* which is extremely simple:
*
* a public class where we add a default constructor (without parameters)
* and the setXXX and getXXX (or isXXX) methods for the properties.
* That's already all for it to work!
*/

import java.awt.*; import java.awt.event.*; import java.beans.*; import java.io.*; import java.util.*; import java.util.List; import javax.swing.*; import javax.swing.tree.*;

public class TreeStatusDemo extends JFrame {

   private JToolBar toolbar;
   private JButton btAdd;
   private JTree tree;
   private TreeModel model;
   private List<TreeNode[]> expanded;
   private int countNew;

   public TreeStatusDemo() {
       super("Tree Status Demo");
       setSize(400, 300);
       setLocationRelativeTo(null);
       setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
       toolbar = new JToolBar();
       btAdd = new JButton("Add Node");
       tree = new JTree();
       toolbar.add(btAdd);
       getContentPane().add(toolbar, BorderLayout.NORTH);
       tree.setEditable(true);
       getContentPane().add(new JScrollPane(tree), BorderLayout.CENTER);
       try {
           deSerialize();
           restoreStatus();
       } catch (Exception e) {
       }
       model = tree.getModel();
       btAdd.addActionListener(new ActionListener() {

           public void actionPerformed(final ActionEvent evt) {
               addNode();
           }
       });
       addWindowListener(new WindowAdapter() {

           public void windowClosing(final WindowEvent e) {
               saveStatus();
               serialize();
               System.exit(0);
           }
       });
   }

   private void saveStatus() {
       //save the expanded Nodes:
       expanded = new ArrayList<TreeNode[]>();
       collectStatusInfo(model.getRoot());
   }

   private void restoreStatus() {
       //expand the saved Nodes:
       for (int i = expanded.size() - 1; i > -1; i--) {
           TreeNode[] ar = expanded.get(i);
           tree.expandPath(new TreePath(ar));
       }
   }

   private void collectStatusInfo(final Object o) {
       int cc = model.getChildCount(o);
       for (int i = 0; i < cc; i++) {
           DefaultMutableTreeNode child = (DefaultMutableTreeNode) model.getChild(o, i);
           TreeNode[] ar = child.getPath();
           if (!model.isLeaf(child) && tree.isExpanded(new TreePath(ar))) {
               expanded.add(ar);
               collectStatusInfo(child);
           }
       }
   }

   private void addNode() {
       TreePath selectedPath = tree.getSelectionPath();
       if (selectedPath == null) {
           return;
       }
       DefaultMutableTreeNode selectedNode = (DefaultMutableTreeNode) selectedPath.getLastPathComponent();
       DefaultMutableTreeNode newChild = new DefaultMutableTreeNode("new node " + countNew++);
       ((DefaultTreeModel) tree.getModel()).insertNodeInto(newChild, selectedNode, selectedNode.getChildCount());
       TreePath newPath = selectedPath.pathByAddingChild(newChild);
       tree.setSelectionPath(newPath);
       tree.startEditingAtPath(newPath);
   }

   public void serialize() {
       try {
           XMLEncoder o = new XMLEncoder(new BufferedOutputStream(new FileOutputStream("tree.xml")));
           o.writeObject(tree.getModel());
           o.writeObject(expanded);
           o.close();
       } catch (IOException e) {
           e.printStackTrace();
       }
   }

   @SuppressWarnings("unchecked")
   private void deSerialize() {
       try {
           XMLDecoder d = new XMLDecoder(new BufferedInputStream(new FileInputStream("tree.xml")));
           tree.setModel((TreeModel) d.readObject());
           expanded = (List<TreeNode[]>) d.readObject();
           d.close();
       } catch (FileNotFoundException ex) {
       }
   }

   public static void main(final String args[]) {
       SwingUtilities.invokeLater(new Runnable() {

           public void run() {
               new TreeStatusDemo().setVisible(true);
           }
       });
   }

}</code=java>