treedragsource.java

来自「java swing 开发代码」· Java 代码 · 共 77 行

// TreeDragSource.java
// A drag source wrapper for a JTree.  This class can be used to make
// a rearrangeable DnD tree with the TransferableTreeNode class as the
// transfer data type.
//

package	jswing.ch24;

import java.awt.dnd.*;
import javax.swing.*;
import javax.swing.tree.*;

public class TreeDragSource 
implements DragSourceListener, DragGestureListener {

  DragSource source;
  DragGestureRecognizer recognizer;
  TransferableTreeNode transferable;
  DefaultMutableTreeNode oldNode;
  JTree sourceTree;

  public TreeDragSource(JTree tree, int actions) {
    sourceTree = tree;
    source = new DragSource();
    recognizer = source.createDefaultDragGestureRecognizer(
		 sourceTree, actions, this);
  }

  /*
   * Drag Gesture Handler
   */
  public void dragGestureRecognized(DragGestureEvent dge) {
    TreePath path = sourceTree.getSelectionPath();
    if ((path == null) || (path.getPathCount() <= 1)) {
      // We can't move the root node or an empty selection
      return;
    }
    oldNode = (DefaultMutableTreeNode)path.getLastPathComponent();
    transferable = new TransferableTreeNode(path);
    source.startDrag(dge, DragSource.DefaultMoveNoDrop, transferable, this);

    // If you support dropping the node anywhere, you should probably
    // start with a valid move cursor:
    //source.startDrag(dge, DragSource.DefaultMoveDrop, transferable, this);
  }

  /*
   * Drag Event Handlers
   */
  public void dragEnter(DragSourceDragEvent dsde) { }
  public void dragExit(DragSourceEvent dse) { }
  public void dragOver(DragSourceDragEvent dsde) { }
  public void dropActionChanged(DragSourceDragEvent dsde) { 
    System.out.println("Action: " + dsde.getDropAction());
    System.out.println("Target Action: " + dsde.getTargetActions());
    System.out.println("User Action: " + dsde.getUserAction());
  }
  public void dragDropEnd(DragSourceDropEvent dsde) {
    /*
     * to support move or copy, we have to check which occurred:
     */
    System.out.println("Drop Action: " + dsde.getDropAction());
    if (dsde.getDropSuccess() &&
        (dsde.getDropAction() == DnDConstants.ACTION_MOVE)) {
      ((DefaultTreeModel)sourceTree.getModel()).removeNodeFromParent(oldNode);
    }

    /*
     * to support move only...
    if (dsde.getDropSuccess()) {
      ((DefaultTreeModel)sourceTree.getModel()).removeNodeFromParent(oldNode);
    }
    */
  }  
}