// public class drag_bsp1 extends JPanel {
import javax.swing.*;
import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.event.*;

public class drag_bsp1 extends JPanel implements ActionListener {
    private JComboBox dropCombo;
    private JList list;
    
    public drag_bsp1() {
        super(new GridLayout(2,1));
        add(createArea());
        add(createList());
    }
    
    private JPanel createList() {
        DefaultListModel listModel = new DefaultListModel();
            
        for (int i = 0; i < 10; i++) {
            listModel.addElement("List Item " + i);
        }
        
        list = new JList(listModel);
        list.setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
        JScrollPane scrollPane = new JScrollPane(list);
        scrollPane.setPreferredSize(new Dimension(400,100));
        
        list.setDragEnabled(true);
        list.setTransferHandler(new ListTransferHandler());
        
        dropCombo = new JComboBox(new String[] {"USE_SELECTION", "ON", "INSERT", "ON_OR_INSERT"});
        dropCombo.addActionListener(this);
        JPanel dropPanel = new JPanel();
        dropPanel.add(new JLabel("List Drop Mode:"));
        dropPanel.add(dropCombo);
        
        JPanel panel = new JPanel(new BorderLayout());
        panel.add(scrollPane, BorderLayout.CENTER);
        panel.add(dropPanel, BorderLayout.SOUTH);
        panel.setBorder(BorderFactory.createTitledBorder("List"));
        return panel;
    }
    
    private JPanel createArea() {
        String text = "Drag from or drop into this area.\nThe default action is MOVE;\nhold the Control key to COPY.";
        
        JTextArea area = new JTextArea();
        area.setText(text);
        area.setDragEnabled(true);
        JScrollPane scrollPane = new JScrollPane(area);
        scrollPane.setPreferredSize(new Dimension(400,100));
        JPanel panel = new JPanel(new BorderLayout());
        panel.add(scrollPane, BorderLayout.CENTER);
        panel.setBorder(BorderFactory.createTitledBorder("Text Area"));
        return panel;
    }

    public void actionPerformed(ActionEvent ae) {
        Object val = dropCombo.getSelectedItem();
        if (val == "USE_SELECTION") {
            list.setDropMode(DropMode.USE_SELECTION);
        } else if (val == "ON") {
            list.setDropMode(DropMode.ON);
        } else if (val == "INSERT") {
            list.setDropMode(DropMode.INSERT);
        } else if (val == "ON_OR_INSERT") {
            list.setDropMode(DropMode.ON_OR_INSERT);
        }
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("DropDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        JComponent newContentPane = new drag_bsp1();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                //Turn off metal's use of bold fonts
	        UIManager.put("swing.boldMetal", Boolean.FALSE);
                createAndShowGUI();
            }
        });
    }
}


class ListTransferHandler extends TransferHandler {
    private int[] indices = null;
    private int addIndex = -1; //Location where items were added
    private int addCount = 0;  //Number of items added.
            
    public boolean canImport(TransferHandler.TransferSupport info) {
        // Check for String flavor
        if (!info.isDataFlavorSupported(DataFlavor.stringFlavor)) {
            return false;
        }
        return true;
   }

    protected Transferable createTransferable(JComponent c) {
        return new StringSelection(exportString(c));
    }
    
    public int getSourceActions(JComponent c) {
        return TransferHandler.COPY_OR_MOVE;
    }
    
    public boolean importData(TransferHandler.TransferSupport info) {
        if (!info.isDrop()) {
            return false;
        }

        JList list = (JList)info.getComponent();
        DefaultListModel listModel = (DefaultListModel)list.getModel();
        JList.DropLocation dl = (JList.DropLocation)info.getDropLocation();
        int index = dl.getIndex();
        boolean insert = dl.isInsert();

        // Get the string that is being dropped.
        Transferable t = info.getTransferable();
        String data;
        try {
            data = (String)t.getTransferData(DataFlavor.stringFlavor);
        } 
        catch (Exception e) { return false; }
                                
        // Perform the actual import.  
        if (insert) {
            listModel.add(index, data);
        } else {
            listModel.set(index, data);
        }
        return true;
    }

    protected void exportDone(JComponent c, Transferable data, int action) {
        cleanup(c, action == TransferHandler.MOVE);
    }

    //Bundle up the selected items in the list
    //as a single string, for export.
    protected String exportString(JComponent c) {
        JList list = (JList)c;
        indices = list.getSelectedIndices();
        Object[] values = list.getSelectedValues();
        
        StringBuffer buff = new StringBuffer();

        for (int i = 0; i < values.length; i++) {
            Object val = values[i];
            buff.append(val == null ? "" : val.toString());
            if (i != values.length - 1) {
                buff.append("\n");
            }
        }
        
        return buff.toString();
    }

    //Take the incoming string and wherever there is a
    //newline, break it into a separate item in the list.
    protected void importString(JComponent c, String str) {
        JList target = (JList)c;
        DefaultListModel listModel = (DefaultListModel)target.getModel();
        int index = target.getSelectedIndex();

        //Prevent the user from dropping data back on itself.
        //For example, if the user is moving items #4,#5,#6 and #7 and
        //attempts to insert the items after item #5, this would
        //be problematic when removing the original items.
        //So this is not allowed.
        if (indices != null && index >= indices[0] - 1 &&
              index <= indices[indices.length - 1]) {
            indices = null;
            return;
        }

        int max = listModel.getSize();
        if (index < 0) {
            index = max;
        } else {
            index++;
            if (index > max) {
                index = max;
            }
        }
        addIndex = index;
        String[] values = str.split("\n");
        addCount = values.length;
        for (int i = 0; i < values.length; i++) {
            listModel.add(index++, values[i]);
        }
    }
    
    //If the remove argument is true, the drop has been
    //successful and it's time to remove the selected items 
    //from the list. If the remove argument is false, it
    //was a Copy operation and the original list is left
    //intact.
    protected void cleanup(JComponent c, boolean remove) {
        if (remove && indices != null) {
            JList source = (JList)c;
            DefaultListModel model  = (DefaultListModel)source.getModel();
            //If we are moving items around in the same list, we
            //need to adjust the indices accordingly, since those
            //after the insertion point have moved.
            if (addCount > 0) {
                for (int i = 0; i < indices.length; i++) {
                    if (indices[i] > addIndex) {
                        indices[i] += addCount;
                    }
                }
            }
            for (int i = indices.length - 1; i >= 0; i--) {
                model.remove(indices[i]);
            }
        }
        indices = null;
        addCount = 0;
        addIndex = -1;
    }
}
