TreeWrapper: An easy way to add Drag and Drop support to JTrees.

TreeWrapper presents an easy way to add Drag and Drop support to any JTree that uses a DefaultTreeModel (or derivative).

For updated information on TreeWrapper visit the TreeWrapper homepage.

This is a list of features and limitations of TreeWrapper:

• Requires JDK5.0
• Any JTree with a DefaultTreeModel (or derivative) will work
• Gives visual feedback to the user about Drag and Drop.
• Minimal interference with custom CellRenderers (only borders are removed)
• Allows for presenting custom popup menus to the user depending on the selected node
• Automatic handling of copy and move operations between nodes in the same or different trees
• TreeTreeDnDListeners are informed about drag and drop operations between trees, and may cancel drag and drop operations and/or handle drag and drop operations themselves
• StringTreeDnDListeners are informed about drag and drop opertaionb between a String provider and a JTree, and again may forbid the drag and drop operation or handle the operation themselves.
• Automatic support for MutableTreeNodes (or derivatives). Does not allow drag and drop operations between plain TreeNodes
• Automatic scrolling support for large JTrees
• Automatically expands collapsed folders to ease the operation

Basic usage.

Using a TreeWrapper is very simple. You just need one line of code:

    JTree myJTree = ...;
    // Add a wrapper around myJTree: That's all, folks!
    TreeWrapper myWrapper = new TreeWrapper( myJTree );
    

Providing custom popup handlers

  class MyCustomPopupHandler
    implements CustomPopupHandler
  {
    public JPopupMenu getMenuAt(JTree aJTree, TreeNode aTreeNode)
    {
      private JPopupMenu myLeafPopupMenu = ...;
      private JPopupMenu myFolderPopupMenu = ...;
      if ( aTreeNode.isLeaf() )
      {
        return myLeafPopupMenu;
      }
      else
      {
        return myFolderPopupMenu;
      }
    }
  }
  ...
  
  MyCustomPopupHandler myHandler = new MyCustomPopupHandler();
  JTree myTree = ...
  // Create a wrapper for myTree
  TreeWrapper myWrapper = new TreeWrapper( myTree );
  // Set the custom popup handler into the wrapper
  myWrapper.setCustomPopupHandler( myHandler );
  
    

Listening to tree-tree drag and drop events

All TreeTreeDnDListeners are informed about drag and drop operations when the user drags a node from a JTree into the same or another JTree (both of them wrapped with respective TreeWrappers, of course).

By implementing a custom TreeTreeDnDListener you can control which nodes can be dragged into which others, and are informed when the drop operation finally happens.

Listening to String-tree drag and drop events

All StringTreeDnDListeners are informed about drag and drop operations between String sources (text fields, for instance, or even the Internet Explorer URL bar) into specific nodes of a JTree. These listeners indicate which nodes accept Strings and which nodes don't. These listeners are also informed when the drop operation happens, and may handle the drop operation themselves (by throwing a DnDVetoException or just let the TreeWrapper to handle the operation itself.