title: how to drag and drop files from a directory in java
body: <p>I want to implement dragging and dropping of files from a directory such as someones hard drive but can't figure out how to do it. I've read the java api but it talks of color pickers and dragging and dropping between lists but how to drag files from a computers file system and drop into my application. I tried writing the transferhandler class and a mouse event for when the drag starts but nothing seems to work. Now I'm back to just having my JFileChooser set so drag has been enabled but how to drop? </p>
  
  <p>Any info or point in the right direction greatly appreciated.</p>
  
  <pre><code>  import javax.swing.*;
  
    import java.awt.BorderLayout;
   import java.awt.GridLayout;
  import java.awt.event.ActionEvent;
  import java.awt.event.ActionListener;
  import java.io.File;
  
  import javax.swing.BorderFactory;
  import javax.swing.DefaultListModel;
  import javax.swing.JButton;
  import javax.swing.JComponent;
  import javax.swing.JFileChooser;
  import javax.swing.JFrame;
  
  import javax.swing.JLabel;
  import javax.swing.JList;
  import javax.swing.JPanel;
  import javax.swing.JScrollPane;
  import javax.swing.SwingUtilities;
  import javax.swing.filechooser.FileFilter;
  
   public class FileChooserDemo
   extends JPanel
   implements ActionListener 
    {
  
  JLabel selectedFileLabel;
   JList selectedFilesList;
   JLabel returnCodeLabel;
  
   public FileChooserDemo() 
      {
   super();
   createContent();
   }
  
  
  void initFrameContent() 
      {
          JPanel closePanel = new JPanel();
          add(closePanel, BorderLayout.SOUTH);
  }
  
  
   private void createContent()
      {
   setLayout(new BorderLayout());
  
          JPanel NorthPanel = new JPanel();
  
       JMenuBar menuBar = new JMenuBar();
          JMenu menu = new JMenu("File");
          JMenuItem quit = new JMenuItem("Quit");
  
          menuBar.add(menu);
          menu.add(quit);
  
          NorthPanel.add(menu,BorderLayout.NORTH);
  
  
    JPanel buttonPanel = new JPanel(new GridLayout(7,1 ));
    JButton openButton = new JButton("Open...");
    openButton.setActionCommand("OPEN");
    openButton.addActionListener(this);
   buttonPanel.add(openButton);
  
   JButton saveButton = new JButton("Save...");
   saveButton.setActionCommand("SAVE");
   saveButton.addActionListener(this);
   buttonPanel.add(saveButton);
  
  
  
  
    JButton delete = new JButton("Delete");
    delete.addActionListener(this);
    delete.setActionCommand("DELETE");
    buttonPanel.add(delete);
  
   add(buttonPanel, BorderLayout.WEST);
  
  
  
   // create a panel to display the selected file(s) and the return code
   JPanel displayPanel = new JPanel(new BorderLayout()); 
   selectedFileLabel = new JLabel("-");
  
   selectedFileLabel.setBorder(BorderFactory.createTitledBorder
   ("Selected File/Directory   "));
  
   displayPanel.add(selectedFileLabel, BorderLayout.NORTH);
  
   selectedFilesList = new JList();
   JScrollPane sp = new JScrollPane(selectedFilesList);
   sp.setBorder(BorderFactory.createTitledBorder("Selected Files "));
   MouseListener listener = new MouseAdapter()
   {
     public void mousePressed(MouseEvent me)
     {
         JComponent comp = (JComponent) me.getSource();
         TransferHandler handler = comp.getTransferHandler();
         handler.exportAsDrag(comp, me, TransferHandler.MOVE);   
     }
   };
   selectedFilesList.addMouseListener(listener);
  
   displayPanel.add(sp);
  
   returnCodeLabel = new JLabel("");
   returnCodeLabel.setBorder(BorderFactory.createTitledBorder("Return Code"));
   displayPanel.add(returnCodeLabel, BorderLayout.SOUTH);
  
   add(displayPanel);
  }
  
  
   public void actionPerformed(ActionEvent e)
      {
            int option = 0;
   File selectedFile = null;
   File[] selectedFiles = new File[0];
  
   if (e.getActionCommand().equals("CLOSE"))
        {
     System.exit(0);
   }
   else if (e.getActionCommand().equals("OPEN"))
          {
       JFileChooser chooser = new JFileChooser();
          chooser.setDragEnabled(true);
          chooser.setMultiSelectionEnabled(true);
       option = chooser.showOpenDialog(this);
       selectedFiles = chooser.getSelectedFiles();
     }
   else if (e.getActionCommand().equals("SAVE"))
          {
       JFileChooser chooser = new JFileChooser();
       option = chooser.showSaveDialog(this);
       selectedFiles = chooser.getSelectedFiles();
     }
  
   // display the selection and return code
   if (selectedFile != null)
     selectedFileLabel.setText(selectedFile.toString());
   else
     selectedFileLabel.setText("null");
   DefaultListModel listModel = new DefaultListModel();
   for (int i =0; i &lt; selectedFiles.length; i++)
     listModel.addElement(selectedFiles[i]);
  
   selectedFilesList.setModel(listModel);
   returnCodeLabel.setText(Integer.toString(option));
   }
  
   public static void main(String[] args) 
      {
   SwingUtilities.invokeLater
   (new Runnable()
         {
      public void run()
           {
        FileChooserDemo app = new FileChooserDemo();
        app.initFrameContent();
        JFrame frame = new JFrame("LoquetUP");
        frame.getContentPane().add(app);
           frame.setDefaultCloseOperation(3);
           frame.setSize(600,400);
           frame.setResizable(false);
           frame.setLocationRelativeTo(null);
  
        //frame.pack();
        frame.setVisible(true);
      }
    });
   }
  
  }
  </code></pre>