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

/**
 * Description:
 * <br/>Copyright (C), 2005-2008, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @author  Yeeku.H.Lee kongyeeku@163.com
 * @version  1.0
 */
public class TestDropTarget
{
	final int DESKTOP_WIDTH = 480;
	final int DESKTOP_HEIGHT = 360;
	final int FRAME_DISTANCE = 30;
	JFrame jf = new JFrame("測試拖放目標——把圖片文件拖入該窗口");
	//定義一個虛擬桌面
	private JDesktopPane desktop = new JDesktopPane();
	//保存下一個內部窗口的座標點
	private int nextFrameX;
	private int nextFrameY;
	//定義內部窗口為虛擬桌面的1/2大小
	private int width = DESKTOP_WIDTH / 2;
	private int height = DESKTOP_HEIGHT / 2;

	public void init()
	{
		desktop.setPreferredSize(new Dimension(DESKTOP_WIDTH, DESKTOP_HEIGHT));
		//將當前窗口創建成拖放源
		new DropTarget(jf, DnDConstants.ACTION_COPY ,  new ImageDropTargetListener());
		jf.add(desktop);
		jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		jf.pack();
		jf.setVisible(true);
	}

	class ImageDropTargetListener extends DropTargetAdapter
	{
		public void drop(DropTargetDropEvent event)
		{
			//接受復制操作
			event.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
			//獲取拖放的內容
			Transferable transferable = event.getTransferable();
			DataFlavor[] flavors = transferable.getTransferDataFlavors();
			//遍歷拖放內容里的所有數據格式
			for (int i = 0; i < flavors.length; i++)
			{  
				DataFlavor d = flavors[i];
				try
				{
					//如果拖放內容的數據格式是文件列表
					if (d.equals(DataFlavor.javaFileListFlavor))
					{
						//取出拖放操作里的文件列表
						java.util.List fileList 
							= (java.util.List) transferable.getTransferData(d);
						for (Object f : fileList)
						{
							//顯示每個文件
							showImage((File)f , event);
						}
					}
				}
				catch (Exception e)
				{  
					e.printStackTrace();
				}
				//強制拖放操作結束，停止阻塞拖放源
				event.dropComplete(true);
			}
		}
		//顯示每個文件的工具方法
		private void showImage(File f , DropTargetDropEvent event)throws java.io.IOException
		{
			Image image = ImageIO.read(f);
			if (image == null)
			{
				//強制拖放操作結束，停止阻塞拖放源
				event.dropComplete(true);
				JOptionPane.showInternalMessageDialog(desktop , "系統不支持這種類型的文件");
				//方法返回，不會繼續操作
				return;
			}
			ImageIcon icon = new ImageIcon(image);
			//創建內部窗口顯示該圖片
			JInternalFrame iframe = new JInternalFrame(f.getName()
				,true , true , true , true);
			JLabel imageLabel = new JLabel(icon);
			iframe.add(new JScrollPane(imageLabel));
			desktop.add(iframe);
			//設置內部窗口的原始位置（內部窗口默認大小是0X0，放在0,0位置）
			iframe.reshape(nextFrameX, nextFrameY, width, height);
			//使該窗口可見，并嘗試選中它
			iframe.show();
			//計算下一個內部窗口的位置
			nextFrameX += FRAME_DISTANCE;
			nextFrameY += FRAME_DISTANCE;
			if (nextFrameX + width > desktop.getWidth()) nextFrameX = 0;
			if (nextFrameY + height > desktop.getHeight()) nextFrameY = 0;
		}
	}
	public static void main(String[] args)
	{
		new TestDropTarget().init();
	}
}