droptargettest.java

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/**
   @version 1.02 2004-08-25
   @author Cay Horstmann
*/

import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.event.*;
import java.awt.dnd.*;
import java.io.*;
import java.util.*;
import javax.swing.*;

/**
   This is a test class to test drag and drop behavior. Drop items into the text area to see the 
   MIME types of the drop target.
*/
public class DropTargetTest
{  
   public static void main(String[] args)
   {  
      JFrame frame = new DropTargetFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

/**
   This frame contains a text area that is a simple drop target.
*/
class DropTargetFrame extends JFrame
{  
   public DropTargetFrame()
   {  
      setTitle("DropTarget");
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

      JTextArea textArea = new JTextArea("Drop items into this text area.\n");

      new DropTarget(textArea, new TextDropTargetListener(textArea));
      add(new JScrollPane(textArea), "Center");
   }

   private static final int DEFAULT_WIDTH = 300;
   private static final int DEFAULT_HEIGHT = 300;
}

/**
   This listener displays the properties of a dropped object.
*/
class TextDropTargetListener implements DropTargetListener
{  
   /**
      Constructs a listener.
      @param aTextArea the text area in which to display the
      properties of the dropped object.
   */
   public TextDropTargetListener(JTextArea aTextArea)
   {  
      textArea = aTextArea;
   }

   public void dragEnter(DropTargetDragEvent event)
   {  
      int a = event.getDropAction();
      if ((a & DnDConstants.ACTION_COPY) != 0)
         textArea.append("ACTION_COPY\n");
      if ((a & DnDConstants.ACTION_MOVE) != 0)
         textArea.append("ACTION_MOVE\n");
      if ((a & DnDConstants.ACTION_LINK) != 0)
         textArea.append("ACTION_LINK\n");

      if (!isDragAcceptable(event))
      {  
         event.rejectDrag();
         return;
      }
   }

   public void dragExit(DropTargetEvent event)
   {
   }

   public void dragOver(DropTargetDragEvent event)
   {  
      // you can provide visual feedback here
   }

   public void dropActionChanged(DropTargetDragEvent event)
   {  
      if (!isDragAcceptable(event))
      {  
         event.rejectDrag();
         return;
      }
   }

   public void drop(DropTargetDropEvent event)
   {  
      if (!isDropAcceptable(event))
      {  
         event.rejectDrop();
         return;
      }

      event.acceptDrop(DnDConstants.ACTION_COPY);

      Transferable transferable = event.getTransferable();

      DataFlavor[] flavors = transferable.getTransferDataFlavors();
      for (int i = 0; i < flavors.length; i++)
      {  
         DataFlavor d = flavors[i];
         textArea.append("MIME type=" + d.getMimeType() + "\n");

         try
         {  
            if (d.equals(DataFlavor.javaFileListFlavor))
            {  
               java.util.List<File> fileList 
                  = (java.util.List<File>) transferable.getTransferData(d);
               for (File f : fileList)
               {  
                  textArea.append(f + "\n");
               }
            }
            else if (d.equals(DataFlavor.stringFlavor))
            {  
               String s = (String) transferable.getTransferData(d);
               textArea.append(s + "\n");
            }
         }
         catch (Exception e)
         {  
            textArea.append(e + "\n");
         }
      }
      textArea.append("\n");
      event.dropComplete(true);
   }

   public boolean isDragAcceptable(DropTargetDragEvent event)
   {  
      // usually, you check the available data flavors here
      // in this program, we accept all flavors
      return (event.getDropAction() & DnDConstants.ACTION_COPY_OR_MOVE) != 0;
   }

   public boolean isDropAcceptable(DropTargetDropEvent event)
   {  
      // usually, you check the available data flavors here
      // in this program, we accept all flavors
      return (event.getDropAction() & DnDConstants.ACTION_COPY_OR_MOVE) != 0;
   }

   private JTextArea textArea;
}