import java.awt.*;
import java.awt.dnd.*;
import java.awt.event.*;
import java.util.Locale;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;

public class DesktopTools extends JFrame implements DropTargetListener {

    private JScrollPane scrollPane;
    private JPanel panel;
    DropTarget dropTarget;
    private int i, j;

    public DesktopTools() {
        setTitle("Tools");
        setSize(370, 200);
        setLocation(100, 100);
        this.setAlwaysOnTop(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        dropTarget = new DropTarget(this, DnDConstants.ACTION_COPY_OR_MOVE,
                this, true, null);
        panel = new JPanel();
        scrollPane = new JScrollPane(panel, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        this.getContentPane().add(scrollPane);
        setVisible(true);
        setResizable(false);
        this.repaint();
    }

    public static void main(String args[]) {
        DesktopTools dt = new DesktopTools();
    }

    @Override
    public void dragEnter(DropTargetDragEvent dtde) {
//        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void dragOver(DropTargetDragEvent dtde) {
//        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void dropActionChanged(DropTargetDragEvent dtde) {
//        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void dragExit(DropTargetEvent dte) {
//        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void drop(DropTargetDropEvent dtde) {
//        throw new UnsupportedOperationException("Not supported yet.");
        int bWidth = 80;
        int bHeight = 80;


        if ((dtde.getDropAction() & DnDConstants.ACTION_COPY_OR_MOVE) != 0) {
            System.out.println("test");
            JButton jb = new JButton("test" + i);

            panel.add(jb);
            jb.setSize(bWidth, bHeight);
            jb.setLocation(5 + (i % 4) * (bWidth + 2), 20 + (j * (bHeight + 2)));
            if (((i + 1) % 4) == 0) {
                j++;
            }
            i++;
            [color=#FFFF00]//panel.updateUI();[/color]
            [color=#FF0000]panel.repaint();[/color]
            this.repaint();

        }
    }
}

    @Override
    public void drop(DropTargetDropEvent dtde) {
        // throw new UnsupportedOperationException("Not supported yet.");
        int bWidth = 80;
        int bHeight = 80;

        if ((dtde.getDropAction() & DnDConstants.ACTION_COPY_OR_MOVE) != 0) {
            System.out.println("test");
            JButton jb = new JButton("test" + i);
            panel.add(jb);
            Dimension d1 = new Dimension(bWidth, bHeight);
            jb.setPreferredSize(d1);
            jb
                    .setLocation(5 + (i % 4) * (bWidth + 2),
                            20 + (j * (bHeight + 2)));
            if (((i + 1) % 4) == 0) {
                Dimension d = new Dimension(this.getWidth(), this.getHeight()
                        + j * bHeight);
                panel.setPreferredSize(d);
                j++;
            }
            i++;
            panel.updateUI();
            panel.repaint();
            this.repaint();

        }
    }