droptargettest.java

《Core Java2 Volume II-5e》源码

/**
 * @version 1.00 1999-09-11
 * @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.*;

public class DropTargetTest
{  public static void main(String[] args)
   {  JFrame frame = new DropTargetFrame();
      frame.show();
   }
}

class DropTargetFrame extends JFrame
{  public DropTargetFrame()
   {  setTitle("DropTarget");
      setSize(300, 300);
      addWindowListener(new WindowAdapter()
         {  public void windowClosing(WindowEvent e)
            {  System.exit(0);
            }
         } );

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

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


class TextDropTargetListener implements DropTargetListener
{  public TextDropTargetListener(JTextArea ta)
   {  textArea = ta;
   }

   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 fileList = (java.util.List)
                  transferable.getTransferData(d);
               Iterator iterator = fileList.iterator();
               while (iterator.hasNext())
               {  File f = (File)iterator.next();
                  textArea.append(f + "\n");
               }
            }
            else if (d.equals(DataFlavor.stringFlavor))
            {  String s = (String)
                  transferable.getTransferData(d);
               textArea.append(s + "\n");
            }
            else if (d.isMimeTypeEqual("text/plain"))
            {  String charset = d.getParameter("charset");
               InputStream in = (InputStream)
                  transferable.getTransferData(d);

               boolean more = true;
               int ch;
               if (charset.equals("ascii"))
               {  do
                  {  ch = in.read();
                     if (ch != 0 && ch != -1)
                        textArea.append("" + (char)ch);
                     else more = false;
                  } while (more);
               }
               else if (charset.equals("unicode"))
               {  boolean littleEndian = true;
                     // if no byte ordering mark, we assume
                     // Windows is the culprit
                  do
                  {  ch = in.read();
                     int ch2 = in.read();
                     if (ch != -1 && littleEndian)
                        ch = (ch & 0xFF) | ((ch2 & 0xFF) << 8);
                     if (ch == 0xFFFE)
                        littleEndian = false;
                     else if (ch != 0 && ch != -1)
                        textArea.append("" + (char)ch);
                     else more = false;
                  } while (more);
               }

               textArea.append("\n");
            }
         }
         catch(Exception e)
         {  textArea.append("Error: " + e + "\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;
}