import java.awt.Color;
 import java.awt.Dimension;
 import java.awt.Graphics;
 import java.awt.Graphics2D;
 import java.awt.Point;
 import java.awt.event.MouseEvent;
 import java.awt.event.MouseListener;
 import java.awt.event.MouseMotionListener;
 import java.awt.event.MouseWheelEvent;
 import java.awt.event.MouseWheelListener;
 import java.awt.geom.AffineTransform;

 import javax.swing.JFrame;
 import javax.swing.JPanel;
 import javax.swing.JScrollPane;


 public class MyAppFrame extends JFrame {

    private JScrollPane scroll;
    private JPanel nullLayoutPanel;
    private JPanel subPanel;
    private double zoomFactor;
    private static Point pressed;

    public MyAppFrame(){
        setSize(200, 200);
        setLocation(50, 50);
        zoomFactor = 1.0;

        nullLayoutPanel = new JPanel(){
            private void zoom() {
                //the zoom logic should perform in here


            }

            //when you try it with the paint method you'll see my problem
            //move the rect by dragging it around then
            //scroll out or in and try to move the rect
            //you'll see that the position of the logical rect doesn't fit with the painted one
            @Override
            public void paint(Graphics g){
                Graphics2D g2d = (Graphics2D) g;
                AffineTransform old = g2d.getTransform();
                g2d.scale(zoomFactor, zoomFactor);
                super.paint(g);
                //old.translate(zoomFactor, zoomFactor);
                g2d.setTransform(old);
            }

        };
        nullLayoutPanel.setPreferredSize(new Dimension(400,400));
        nullLayoutPanel.setLayout(null);
        nullLayoutPanel.addMouseWheelListener(new MouseWheelListener() {

            @Override
            public void mouseWheelMoved(MouseWheelEvent e) {
                if (e.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL){
                    if((.1 * e.getWheelRotation()) > 0 && zoomFactor < 2.0){
                        zoomFactor += (.1 * e.getWheelRotation());
                    } else if((.1 * e.getWheelRotation()) < 0 && zoomFactor > 0.1){
                        zoomFactor += (.1 * e.getWheelRotation());
                    }
                    zoomFactor = Math.round(zoomFactor*10.0)/10.0;
                    nullLayoutPanel.repaint();
                }
            }
        });


        scroll = new JScrollPane(nullLayoutPanel);
        scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
        getContentPane().add(scroll);

        subPanel = new JPanel(){
            @Override
            public void paint(Graphics g){
                g.setColor(Color.BLUE);
                g.fillRect(0, 0, this.getWidth(), this.getHeight());
            }
        };

        subPanel.addMouseListener(new MouseListener() {

            @Override
            public void mouseReleased(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mousePressed(MouseEvent e) {
                pressed = e.getPoint();
            }

            @Override
            public void mouseExited(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mouseEntered(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mouseClicked(MouseEvent e) {
                // TODO Auto-generated method stub

            }
        });
        subPanel.addMouseMotionListener(new MouseMotionListener() {

            @Override
            public void mouseMoved(MouseEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void mouseDragged(MouseEvent e) {
                Point pPoint;
                pPoint = subPanel.getLocation();
                int x = (int)(pPoint.x - pressed.getX()+e.getX());
                int y = (int)(pPoint.y - pressed.getY()+e.getY());
                if(x>0&&y>0)
                    subPanel.setLocation(x,y);
            }
        });

        subPanel.setBounds(10, 10, 10, 10);
        nullLayoutPanel.add(subPanel);


        setVisible(true);

    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        new MyAppFrame();
    }

 }