Java – drag and drop nodes in JTree

I can't create a JTree that allows you to reorganize nodes by dragging and dropping in JTree It seems that this should be relatively simple I've looked at the example online, but I don't seem to be able to implement it in my own code

For example, this provided by sun allows you to drag between different components into the tree instead of from inside the tree

And I also found that in this way, you can drag text into JTree instead of in the tree

import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
import javax.swing.tree.*;

public class DndTree {

    public static void main(String args[]) {
        Runnable runner = new Runnable()  {

            public void run() {
                JFrame f = new JFrame("D-n-D JTree");
                f.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);

                JPanel top = new JPanel(new BorderLayout());
                JLabel dragLabel = new JLabel("Drag me:");
                JTextField text = new JTextField();
                text.setDragEnabled(true);
                top.add(dragLabel,BorderLayout.WEST);
                top.add(text,BorderLayout.CENTER);
                f.add(top,BorderLayout.NORTH);

                final JTree tree = new JTree();
                final DefaultTreeModel model = (DefaultTreeModel) tree.getModel();
                tree.setTransferHandler(new TransferHandler()  {

                    public boolean canImport(TransferHandler.TransferSupport support) {
                        if (!support.isDataFlavorSupported(DataFlavor.stringFlavor)
                                || !support.isDrop()) {
                            return false;
                        }

                        JTree.DropLocation dropLocation =
                                (JTree.DropLocation) support.getDropLocation();

                        return dropLocation.getPath() != null;
                    }

                    public boolean importData(TransferHandler.TransferSupport support) {
                        if (!canImport(support)) {
                            return false;
                        }

                        JTree.DropLocation dropLocation =
                                (JTree.DropLocation) support.getDropLocation();

                        TreePath path = dropLocation.getPath();

                        Transferable transferable = support.getTransferable();

                        String transferData;
                        try {
                            transferData = (String) transferable.getTransferData(
                                    DataFlavor.stringFlavor);
                        } catch (IOException e) {
                            return false;
                        } catch (UnsupportedFlavorException e) {
                            return false;
                        }

                        int childIndex = dropLocation.getChildIndex();
                        if (childIndex == -1) {
                            childIndex = model.getChildCount(path.getLastPathComponent());
                        }

                        DefaultMutableTreeNode newNode =
                                new DefaultMutableTreeNode(transferData);
                        DefaultMutableTreeNode parentNode =
                                (DefaultMutableTreeNode) path.getLastPathComponent();
                        model.insertNodeInto(newNode,parentNode,childIndex);

                        TreePath newPath = path.pathByAddingChild(newNode);
                        tree.makeVisible(newPath);
                        tree.scrollRectToVisible(tree.getPathBounds(newPath));

                        return true;
                    }
                });

                JScrollPane pane = new JScrollPane(tree);
                f.add(pane,BorderLayout.CENTER);

                JPanel bottom = new JPanel();
                JLabel comboLabel = new JLabel("DropMode");
                String options[] = {"USE_SELECTION","ON","INSERT","ON_OR_INSERT"
                };
                final DropMode mode[] = {DropMode.USE_SELECTION,DropMode.ON,DropMode.INSERT,DropMode.ON_OR_INSERT};
                final JCombo@R_807_2419@ combo = new JCombo@R_807_2419@(options);
                combo.addActionListener(new ActionListener()  {

                    public void actionPerformed(ActionEvent e) {
                        int selectedIndex = combo.getSelectedIndex();
                        tree.setDropMode(mode[selectedIndex]);
                    }
                });
                bottom.add(comboLabel);
                bottom.add(combo);
                f.add(bottom,BorderLayout.soUTH);
                f.setSize(300,400);
                f.setVisible(true);
            }
        };
        EventQueue.invokelater(runner);
    }
}

Any reference or suggestion will be huge thank you

Solution

This has not been done before, but a fast Google search raises the same question here: http://www.coderanch.com/t/346509/GUI/java/JTree-drag-drop-inside-one It has a visible work implementation

The following are the relevant codes issued by Craig wood:

import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.util.*;
import java.util.List;
import javax.swing.*;
import javax.swing.tree.*;

public class TreeDragAndDrop {
    private JScrollPane getContent() {
        JTree tree = new JTree();
        tree.setDragEnabled(true);
        tree.setDropMode(DropMode.ON_OR_INSERT);
        tree.setTransferHandler(new TreeTransferHandler());
        tree.getSelectionModel().setSelectionMode(
                TreeSelectionModel.CONTIGUOUS_TREE_SELECTION);
        expandTree(tree);
        return new JScrollPane(tree);
    }

    private void expandTree(JTree tree) {
        DefaultMutableTreeNode root =
            (DefaultMutableTreeNode)tree.getModel().getRoot();
        Enumeration e = root.breadthFirstEnumeration();
        while(e.hasMoreElements()) {
            DefaultMutableTreeNode node =
                (DefaultMutableTreeNode)e.nextElement();
            if(node.isLeaf()) continue;
            int row = tree.getRowForPath(new TreePath(node.getPath()));
            tree.expandRow(row);
        }
    }

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new TreeDragAndDrop().getContent());
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}

class TreeTransferHandler extends TransferHandler {
    DataFlavor nodesFlavor;
    DataFlavor[] flavors = new DataFlavor[1];
    DefaultMutableTreeNode[] nodesToRemove;

    public TreeTransferHandler() {
        try {
            String mimeType = DataFlavor.javaJVMLocalObjectMimeType +
                              ";class=\"" +
                javax.swing.tree.DefaultMutableTreeNode[].class.getName() +
                              "\"";
            nodesFlavor = new DataFlavor(mimeType);
            flavors[0] = nodesFlavor;
        } catch(ClassNotFoundException e) {
            System.out.println("ClassNotFound: " + e.getMessage());
        }
    }

    public boolean canImport(TransferHandler.TransferSupport support) {
        if(!support.isDrop()) {
            return false;
        }
        support.setShowDropLocation(true);
        if(!support.isDataFlavorSupported(nodesFlavor)) {
            return false;
        }
        // Do not allow a drop on the drag source selections.
        JTree.DropLocation dl =
                (JTree.DropLocation)support.getDropLocation();
        JTree tree = (JTree)support.getComponent();
        int dropRow = tree.getRowForPath(dl.getPath());
        int[] selRows = tree.getSelectionRows();
        for(int i = 0; i < selRows.length; i++) {
            if(selRows[i] == dropRow) {
                return false;
            }
        }
        // Do not allow MOVE-action drops if a non-leaf node is
        // selected unless all of its children are also selected.
        int action = support.getDropAction();
        if(action == MOVE) {
            return haveCompleteNode(tree);
        }
        // Do not allow a non-leaf node to be copied to a level
        // which is less than its source level.
        TreePath dest = dl.getPath();
        DefaultMutableTreeNode target =
            (DefaultMutableTreeNode)dest.getLastPathComponent();
        TreePath path = tree.getPathForRow(selRows[0]);
        DefaultMutableTreeNode firstNode =
            (DefaultMutableTreeNode)path.getLastPathComponent();
        if(firstNode.getChildCount() > 0 &&
               target.getLevel() < firstNode.getLevel()) {
            return false;
        }
        return true;
    }

    private boolean haveCompleteNode(JTree tree) {
        int[] selRows = tree.getSelectionRows();
        TreePath path = tree.getPathForRow(selRows[0]);
        DefaultMutableTreeNode first =
            (DefaultMutableTreeNode)path.getLastPathComponent();
        int childCount = first.getChildCount();
        // first has children and no children are selected.
        if(childCount > 0 && selRows.length == 1)
            return false;
        // first may have children.
        for(int i = 1; i < selRows.length; i++) {
            path = tree.getPathForRow(selRows[i]);
            DefaultMutableTreeNode next =
                (DefaultMutableTreeNode)path.getLastPathComponent();
            if(first.isNodeChild(next)) {
                // Found a child of first.
                if(childCount > selRows.length-1) {
                    // Not all children of first are selected.
                    return false;
                }
            }
        }
        return true;
    }

    protected Transferable createTransferable(JComponent c) {
        JTree tree = (JTree)c;
        TreePath[] paths = tree.getSelectionPaths();
        if(paths != null) {
            // Make up a node array of copies for transfer and
            // another for/of the nodes that will be removed in
            // exportDone after a successful drop.
            List<DefaultMutableTreeNode> copies =
                new ArrayList<DefaultMutableTreeNode>();
            List<DefaultMutableTreeNode> toRemove =
                new ArrayList<DefaultMutableTreeNode>();
            DefaultMutableTreeNode node =
                (DefaultMutableTreeNode)paths[0].getLastPathComponent();
            DefaultMutableTreeNode copy = copy(node);
            copies.add(copy);
            toRemove.add(node);
            for(int i = 1; i < paths.length; i++) {
                DefaultMutableTreeNode next =
                    (DefaultMutableTreeNode)paths[i].getLastPathComponent();
                // Do not allow higher level nodes to be added to list.
                if(next.getLevel() < node.getLevel()) {
                    break;
                } else if(next.getLevel() > node.getLevel()) {  // child node
                    copy.add(copy(next));
                    // node already contains child
                } else {                                        // sibling
                    copies.add(copy(next));
                    toRemove.add(next);
                }
            }
            DefaultMutableTreeNode[] nodes =
                copies.toArray(new DefaultMutableTreeNode[copies.size()]);
            nodesToRemove =
                toRemove.toArray(new DefaultMutableTreeNode[toRemove.size()]);
            return new NodesTransferable(nodes);
        }
        return null;
    }

    /** Defensive copy used in createTransferable. */
    private DefaultMutableTreeNode copy(TreeNode node) {
        return new DefaultMutableTreeNode(node);
    }

    protected void exportDone(JComponent source,Transferable data,int action) {
        if((action & MOVE) == MOVE) {
            JTree tree = (JTree)source;
            DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
            // Remove nodes saved in nodesToRemove in createTransferable.
            for(int i = 0; i < nodesToRemove.length; i++) {
                model.removeNodeFromParent(nodesToRemove[i]);
            }
        }
    }

    public int getSourceActions(JComponent c) {
        return COPY_OR_MOVE;
    }

    public boolean importData(TransferHandler.TransferSupport support) {
        if(!canImport(support)) {
            return false;
        }
        // Extract transfer data.
        DefaultMutableTreeNode[] nodes = null;
        try {
            Transferable t = support.getTransferable();
            nodes = (DefaultMutableTreeNode[])t.getTransferData(nodesFlavor);
        } catch(UnsupportedFlavorException ufe) {
            System.out.println("UnsupportedFlavor: " + ufe.getMessage());
        } catch(java.io.IOException ioe) {
            System.out.println("I/O error: " + ioe.getMessage());
        }
        // Get drop location info.
        JTree.DropLocation dl =
                (JTree.DropLocation)support.getDropLocation();
        int childIndex = dl.getChildIndex();
        TreePath dest = dl.getPath();
        DefaultMutableTreeNode parent =
            (DefaultMutableTreeNode)dest.getLastPathComponent();
        JTree tree = (JTree)support.getComponent();
        DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
        // Configure for drop mode.
        int index = childIndex;    // DropMode.INSERT
        if(childIndex == -1) {     // DropMode.ON
            index = parent.getChildCount();
        }
        // Add data to model.
        for(int i = 0; i < nodes.length; i++) {
            model.insertNodeInto(nodes[i],parent,index++);
        }
        return true;
    }

    public String toString() {
        return getClass().getName();
    }

    public class NodesTransferable implements Transferable {
        DefaultMutableTreeNode[] nodes;

        public NodesTransferable(DefaultMutableTreeNode[] nodes) {
            this.nodes = nodes;
         }

        public Object getTransferData(DataFlavor flavor)
                                 throws UnsupportedFlavorException {
            if(!isDataFlavorSupported(flavor))
                throw new UnsupportedFlavorException(flavor);
            return nodes;
        }

        public DataFlavor[] getTransferDataFlavors() {
            return flavors;
        }

        public boolean isDataFlavorSupported(DataFlavor flavor) {
            return nodesFlavor.equals(flavor);
        }
    }
}