[JTree] Drag and drop

Un truc dans ce genre, qui permet aussi bien de deplacer des noeuds dans un arbre que de "dropper" la chaine de texte du noeud selectionne dans Word par exempe :

Code :

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package test;
 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
 
/**
 * <p>Title: </p>
 *
 * <p>Description: </p>
 *
 * <p>Copyright: Copyright (c) 2005</p>
 *
 * <p>Company: </p>
 *
 * @author not attributable
 * @version 1.0
 */
class Test {
  public Test() {
  }
 
  public static void main(String ...args) {
    DefaultTreeModel treeModel = createTreeModel();
    JTree tree = new JTree(treeModel);
    TreeSelectionModel treeSelectionModel = new DefaultTreeSelectionModel();
    treeSelectionModel.setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
    tree.setSelectionModel(treeSelectionModel);
    tree.setDragEnabled(true);
    tree.setTransferHandler(new TreeTransfertHandler());
    JFrame frame = new JFrame("Test");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLayout(new BorderLayout());
    frame.add(new JScrollPane(tree));
    frame.setSize(400, 300);
    frame.setVisible(true);
  }
 
  private static DefaultTreeModel createTreeModel() {
    DefaultMutableTreeNode root = createTreeNode(null, 5, 0);
    DefaultTreeModel result = new DefaultTreeModel(root);
    return result;
  }
 
  private static DefaultMutableTreeNode createTreeNode(DefaultMutableTreeNode parent, int level, int index) {
    if (level == 0) {
      return null;
    }
    DefaultMutableTreeNode node = new DefaultMutableTreeNode();
    StringBuilder buffer = new StringBuilder();
    if (parent != null) {
      buffer.append(parent.getUserObject());
      buffer.append("-");
    }
    buffer.append(index);
    String name = buffer.toString();
    node.setUserObject(name);
    level--;
    for (int i = 0; i < level; i++) {
      DefaultMutableTreeNode child = createTreeNode(node, level, i);
      if (child != null) {
        node.add(child);
      }
    }
    return node;
  }
}

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package test;
 
import java.awt.*;
import java.awt.datatransfer.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.tree.*;
 
/**
 * <p>Title: </p>
 *
 * <p>Description: </p>
 *
 * <p>Copyright: Copyright (c) 2005</p>
 *
 * <p>Company: </p>
 *
 * @author not attributable
 * @version 1.0
 */
class TreeTransfertHandler extends TransferHandler {
  /** Last imported tree node.
   */
  private DefaultMutableTreeNode importedNode = null;
 
  /** Creates a new instance.
   */
  public TreeTransfertHandler() {
  }
 
 
  /** {@inheritDoc}
   * <BR>As of Java 1.4.x and 5.0 this method does not work properly (see bug <A HREF="http://developer.java.sun.com/developer/bugParade/bugs/4816922.html">#4816922</A> at Sun's web site).
   */
  @Override public Icon getVisualRepresentation(Transferable t) {
    return super.getVisualRepresentation(t);
  }
 
  /** {@inheritDoc}
   */
  @Override protected Transferable createTransferable(JComponent component) {
    String entity = exportEntity(component);
    // We could use a better transferable that could handle several dataflavors (text+image+treePath to node+....) at once.
    // So far this one is good for this TransferHandler and to ANY (including non-Java) app that can receive the STRING_FLAVOR.
    return new StringSelection(entity);
  }
 
  /** {@inheritDoc}
   */
  @Override protected void exportDone(JComponent c, Transferable data, int action) {
    cleanup(c, action == MOVE);
  }
 
  /////////////////////////////////
  // TransferHelper overloading. //
  /////////////////////////////////
 
  /** {@inheritDoc}
   */
  @Override public int getSourceActions(JComponent component) {
    JTree tree = (JTree) component;
    Object lastPathComponent = tree.getSelectionPath().getLastPathComponent();
    if (lastPathComponent instanceof DefaultMutableTreeNode) {
      DefaultMutableTreeNode node = (DefaultMutableTreeNode) lastPathComponent;
      Object obj = node.getUserObject();
      if (obj instanceof String) {
        return COPY_OR_MOVE;
      }
    }
    return NONE;
  }
 
  /** {@inheritDoc}
   */
  @Override public boolean canImport(JComponent component, DataFlavor[] flavors) {
    for (DataFlavor f : flavors) {
      // We can only import STRING_FLAVOR (plain text) so far.
      // We may add additional data flavors here in the future.
      if (DataFlavor.stringFlavor.equals(f)) {
        return true;
      }
    }
    return false;
  }
 
  /** {@inheritDoc}
   */
  @Override public boolean importData(JComponent component, Transferable t) {
    if (canImport(component, t.getTransferDataFlavors())) {
      try {
        // Remember as of now, we can only deal with STRING_FLAVOR.
        String text = (String) t.getTransferData(DataFlavor.stringFlavor);
        // We cheat, normally we should look into the tree for the proper node.
        // We could export the tree path to the node as a custom data flavor.
        // We have to test this when doing DnD with 2 different trees.
        return importEntity((JTree) component, importedNode);
      }
      catch (UnsupportedFlavorException ufe) {
        System.err.println(ufe);
      }
      catch (IOException ioe) {
        System.err.println(ioe);
      }
    }
    return false;
  }
 
  /////////////////////////
  // Convenient methods. //
  /////////////////////////
 
  /** Exports an entity from a component.
   * @param component The source component.
   * @return The entity to be exported.
   */
  public String exportEntity(JComponent component) {
    JTree tree = (JTree) component;
    Object lastPathComponent = tree.getSelectionPath().getLastPathComponent();
    if (lastPathComponent instanceof DefaultMutableTreeNode) {
      DefaultMutableTreeNode node = (DefaultMutableTreeNode) lastPathComponent;
      Object obj = node.getUserObject();
      if (obj instanceof String) {
        importedNode = node;
        return (String) obj;
      }
    }
    return null;
  }
 
  /** Imports a string to a component.
   * @param component The target component.
   * @param importedNode The node to import.
   * @return <code>True</code> if import was successfull, <code>false</code> otherwise.
   */
  public boolean importEntity(JComponent component, DefaultMutableTreeNode importedNode) {
    JTree tree = (JTree) component;
    Object lastPathComponent = tree.getSelectionPath().getLastPathComponent();
    if (lastPathComponent instanceof DefaultMutableTreeNode) {
      DefaultMutableTreeNode targetNode = (DefaultMutableTreeNode) lastPathComponent;
      TreeNode rootNode = targetNode.getRoot();
      Enumeration ancestorEnumeration = targetNode.pathFromAncestorEnumeration(rootNode);
      // Verify we do not try to move the node to one of its sub-nodes.
      while (ancestorEnumeration.hasMoreElements()) {
        DefaultMutableTreeNode ancestorNode = (DefaultMutableTreeNode) ancestorEnumeration.nextElement();
        if (ancestorNode.equals(importedNode)) {
          System.err.println("Cannot import " + importedNode + " because " + ancestorNode + " is part of the path from " + targetNode + " to " + rootNode);
          return false;
        }
      }
      DefaultTreeModel model = (DefaultTreeModel) tree.getModel();
      // Create a copy of the node structure.
      DefaultMutableTreeNode nodeCopy = duplicateNodeStructure(importedNode);
      model.insertNodeInto(nodeCopy, targetNode, 0);
      return true;
    }
    return false;
  }
 
  /** Cleanup after export.
   * @param component The source component.
   * @param remove <CODE>True</CODE> if the selection should be removed from the component; <CODE>false</CODE> otherwise.
   */
  protected void cleanup(JComponent component, boolean remove) {
    JTree tree = (JTree) component;
    // Remove string node from parent node.
    if (remove) {
      DefaultTreeModel model = (DefaultTreeModel) tree.getModel();
      model.removeNodeFromParent(importedNode);
    }
    // Clean references.
    importedNode = null;
  }
 
  /** Duplicate a node structure.
   * @param sourceNode The source node.
   * @return A copy of the given node and all its sub-nodes.
   */
  private DefaultMutableTreeNode duplicateNodeStructure(DefaultMutableTreeNode sourceNode) {
    if (sourceNode == null) {
      return null;
    }
    DefaultMutableTreeNode result = new DefaultMutableTreeNode(sourceNode.getUserObject());
    Enumeration childrenEnumeration = sourceNode.children();
    while (childrenEnumeration.hasMoreElements()) {
      DefaultMutableTreeNode child = duplicateNodeStructure((DefaultMutableTreeNode) childrenEnumeration.nextElement());
      result.add(child);
    }
    return result;
  }
}

Effectivement le code du handler a l'air plus simple/court. Ah c'est bien ca de pouvoir specifier le mode de drop dans l'arbre (vivement la version finale de Java 6).

EDIT - je viens de jeter un coup d'oeuil a la javadoc de Mustang c'est vrai que les classe TransferHandler.TransferInfo et TransferHandler.DropLocation semblent bien pratiques.

Note : la javadoc de la methode TransferHandler.shouldIndicate() n'indique pas qu'elle a ete rajoutee dans la 1.6